diff --git a/.gitignore b/.gitignore
index 208b808d..e95cbaa8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,7 @@ bin/
 /CMakeScripts
 /doc/doxyxml
 /doc/html
+/doc/node_modules
 virtualenv
 /Testing
 /install_manifest.txt
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b2e2ad7b..977090f7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,15 +24,23 @@ function(join result_var)
   set(${result_var} "${result}" PARENT_SCOPE)
 endfunction()
 
+include(CMakeParseArguments)
+
 # Sets a cache variable with a docstring joined from multiple arguments:
 #   set(<variable> <value>... CACHE <type> <docstring>...)
 # This allows splitting a long docstring for readability.
 function(set_verbose)
-  cmake_parse_arguments(SET_VERBOSE "" "" "CACHE" ${ARGN})
-  list(GET SET_VERBOSE_CACHE 0 type)
-  list(REMOVE_AT SET_VERBOSE_CACHE 0)
-  join(doc ${SET_VERBOSE_CACHE})
-  set(${SET_VERBOSE_UNPARSED_ARGUMENTS} CACHE ${type} ${doc})
+  # cmake_parse_arguments is broken in CMake 3.4 (cannot parse CACHE) so use
+  # list instead.
+  list(GET ARGN 0 var)
+  list(REMOVE_AT ARGN 0)
+  list(GET ARGN 0 val)
+  list(REMOVE_AT ARGN 0)
+  list(REMOVE_AT ARGN 0)
+  list(GET ARGN 0 type)
+  list(REMOVE_AT ARGN 0)
+  join(doc ${ARGN})
+  set(${var} ${val} CACHE ${type} ${doc})
 endfunction()
 
 # Set the default CMAKE_BUILD_TYPE to Release.
@@ -44,6 +52,12 @@ if (MASTER_PROJECT AND NOT CMAKE_BUILD_TYPE)
               "CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel.")
 endif ()
 
+project(FMT CXX)
+include(GNUInstallDirs)
+set_verbose(FMT_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR} CACHE STRING
+            "Installation directory for include files, a relative path "
+            "that will be joined to ${CMAKE_INSTALL_PREFIX}, or an arbitrary absolute path.")
+
 option(FMT_PEDANTIC "Enable extra warnings and expensive tests." OFF)
 option(FMT_WERROR "Halt the compilation with an error on compiler warnings."
        OFF)
@@ -54,8 +68,7 @@ option(FMT_INSTALL "Generate the install target." ${MASTER_PROJECT})
 option(FMT_TEST "Generate the test target." ${MASTER_PROJECT})
 option(FMT_FUZZ "Generate the fuzz target." OFF)
 option(FMT_CUDA_TEST "Generate the cuda-test target." OFF)
-
-project(FMT CXX)
+option(FMT_OS "Include core requiring OS (Windows/Posix) " ON)
 
 # Get version from core.h
 file(READ include/fmt/core.h core_h)
@@ -81,6 +94,7 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}
 
 include(cxx14)
 include(CheckCXXCompilerFlag)
+include(JoinPaths)
 
 list(FIND CMAKE_CXX_COMPILE_FEATURES "cxx_variadic_templates" index)
 if (${index} GREATER -1)
@@ -173,7 +187,11 @@ endfunction()
 # Define the fmt library, its includes and the needed defines.
 add_headers(FMT_HEADERS chrono.h color.h compile.h core.h format.h format-inl.h
                         locale.h os.h ostream.h posix.h printf.h ranges.h)
-set(FMT_SOURCES src/format.cc src/os.cc)
+if (FMT_OS)
+  set(FMT_SOURCES src/format.cc src/os.cc)
+else()
+  set(FMT_SOURCES src/format.cc)
+endif ()
 
 add_library(fmt ${FMT_SOURCES} ${FMT_HEADERS} README.rst ChangeLog.rst)
 add_library(fmt::fmt ALIAS fmt)
@@ -182,6 +200,10 @@ if (HAVE_STRTOD_L)
   target_compile_definitions(fmt PUBLIC FMT_LOCALE)
 endif ()
 
+if (MINGW)
+  target_compile_options(fmt PUBLIC "-Wa,-mbig-obj")
+endif ()
+
 if (FMT_WERROR)
   target_compile_options(fmt PRIVATE ${WERROR_FLAG})
 endif ()
@@ -193,7 +215,7 @@ target_compile_features(fmt INTERFACE ${FMT_REQUIRED_FEATURES})
 
 target_include_directories(fmt PUBLIC
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:include>)
+  $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
 
 set(FMT_DEBUG_POSTFIX d CACHE STRING "Debug library postfix.")
 
@@ -209,7 +231,7 @@ if (CMAKE_BUILD_TYPE STREQUAL "Debug")
 endif ()
 
 if (BUILD_SHARED_LIBS)
-  if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS")
+  if (UNIX AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} MATCHES "SunOS" AND NOT EMSCRIPTEN)
     # Fix rpmlint warning:
     # unused-direct-shlib-dependency /usr/lib/libformat.so.1.1.0 /lib/libm.so.6.
     target_link_libraries(fmt -Wl,--as-needed)
@@ -228,42 +250,36 @@ target_compile_features(fmt-header-only INTERFACE ${FMT_REQUIRED_FEATURES})
 
 target_include_directories(fmt-header-only INTERFACE
   $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:include>)
+  $<INSTALL_INTERFACE:${FMT_INC_DIR}>)
 
 # Install targets.
 if (FMT_INSTALL)
-  include(GNUInstallDirs)
   include(CMakePackageConfigHelpers)
   set_verbose(FMT_CMAKE_DIR ${CMAKE_INSTALL_LIBDIR}/cmake/fmt CACHE STRING
-              "Installation directory for cmake files, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
+              "Installation directory for cmake files, a relative path "
+              "that will be joined to ${CMAKE_INSTALL_PREFIX}, or an arbitrary absolute path.")
   set(version_config ${PROJECT_BINARY_DIR}/fmt-config-version.cmake)
   set(project_config ${PROJECT_BINARY_DIR}/fmt-config.cmake)
   set(pkgconfig ${PROJECT_BINARY_DIR}/fmt.pc)
   set(targets_export_name fmt-targets)
 
-  set (INSTALL_TARGETS fmt)
-  if (TARGET fmt-header-only)
-    set(INSTALL_TARGETS ${INSTALL_TARGETS} fmt-header-only)
-  endif ()
-
   set_verbose(FMT_LIB_DIR ${CMAKE_INSTALL_LIBDIR} CACHE STRING
-              "Installation directory for libraries, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
-
-  set_verbose(FMT_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR}/fmt CACHE STRING
-              "Installation directory for include files, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
+              "Installation directory for libraries, a relative path "
+              "that will be joined to ${CMAKE_INSTALL_PREFIX}, or an arbitrary absolute path.")
 
   set_verbose(FMT_PKGCONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/pkgconfig CACHE PATH
-              "Installation directory for pkgconfig (.pc) files, relative to "
-              "${CMAKE_INSTALL_PREFIX}.")
+              "Installation directory for pkgconfig (.pc) files, a relative path "
+              "that will be joined to ${CMAKE_INSTALL_PREFIX}, or an arbitrary absolute path.")
 
   # Generate the version, config and target files into the build directory.
   write_basic_package_version_file(
     ${version_config}
     VERSION ${FMT_VERSION}
     COMPATIBILITY AnyNewerVersion)
+
+  join_paths(libdir_for_pc_file "\${exec_prefix}" "${FMT_LIB_DIR}")
+  join_paths(includedir_for_pc_file "\${prefix}" "${FMT_INC_DIR}")
+
   configure_file(
     "${PROJECT_SOURCE_DIR}/support/cmake/fmt.pc.in"
     "${pkgconfig}"
@@ -272,6 +288,8 @@ if (FMT_INSTALL)
     ${PROJECT_SOURCE_DIR}/support/cmake/fmt-config.cmake.in
     ${project_config}
     INSTALL_DESTINATION ${FMT_CMAKE_DIR})
+
+  set(INSTALL_TARGETS fmt fmt-header-only)
   # Use a namespace because CMake provides better diagnostics for namespaced
   # imported targets.
   export(TARGETS ${INSTALL_TARGETS} NAMESPACE fmt::
@@ -292,7 +310,7 @@ if (FMT_INSTALL)
 
   install(FILES $<TARGET_PDB_FILE:${INSTALL_TARGETS}>
           DESTINATION ${FMT_LIB_DIR} OPTIONAL)
-  install(FILES ${FMT_HEADERS} DESTINATION ${FMT_INC_DIR})
+  install(FILES ${FMT_HEADERS} DESTINATION "${FMT_INC_DIR}/fmt")
   install(FILES "${pkgconfig}" DESTINATION "${FMT_PKGCONFIG_DIR}")
 endif ()
 
@@ -308,6 +326,7 @@ endif ()
 # Control fuzzing independent of the unit tests.
 if (FMT_FUZZ)
   add_subdirectory(test/fuzzing)
+  target_compile_definitions(fmt PUBLIC FMT_FUZZ)
 endif ()
 
 set(gitignore ${PROJECT_SOURCE_DIR}/.gitignore)
diff --git a/ChangeLog.rst b/ChangeLog.rst
index 8e581c47..97a0a7da 100644
--- a/ChangeLog.rst
+++ b/ChangeLog.rst
@@ -1,3 +1,349 @@
+7.0.3 - 2020-08-06
+------------------
+
+* Worked around broken ``numeric_limits`` for 128-bit integers
+  (`#1787 <https://github.com/fmtlib/fmt/issues/1787>`_).
+
+* Added error reporting on missing named arguments
+  (`#1796 <https://github.com/fmtlib/fmt/issues/1796>`_).
+
+* Stopped using 128-bit integers with clang-cl
+  (`#1800 <https://github.com/fmtlib/fmt/pull/1800>`_).
+  Thanks `@Kingcom <https://github.com/Kingcom>`_.
+
+* Fixed issues in locale-specific integer formatting
+  (`#1782 <https://github.com/fmtlib/fmt/issues/1782>`_,
+  `#1801 <https://github.com/fmtlib/fmt/issues/1801>`_).
+
+7.0.2 - 2020-07-29
+------------------
+
+* Worked around broken ``numeric_limits`` for 128-bit integers
+  (`#1725 <https://github.com/fmtlib/fmt/issues/1725>`_).
+
+* Fixed compatibility with CMake 3.4
+  (`#1779 <https://github.com/fmtlib/fmt/issues/1779>`_).
+
+* Fixed handling of digit separators in locale-specific formatting
+  (`#1782 <https://github.com/fmtlib/fmt/issues/1782>`_).
+
+7.0.1 - 2020-07-07
+------------------
+
+* Updated the inline version namespace name.
+
+* Worked around a gcc bug in mangling of alias templates
+  (`#1753 <https://github.com/fmtlib/fmt/issues/1753>`_).
+
+* Fixed a linkage error on Windows
+  (`#1757 <https://github.com/fmtlib/fmt/issues/1757>`_).
+  Thanks `@Kurkin (Dmitry Kurkin) <https://github.com/Kurkin>`_.
+
+* Fixed minor issues with the documentation.
+
+7.0.0 - 2020-07-05
+------------------
+
+* Reduced the library size. For example, on macOS a stripped test binary
+  statically linked with {fmt} `shrank from ~368k to less than 100k
+  <http://www.zverovich.net/2020/05/21/reducing-library-size.html>`_.
+
+* Added a simpler and more efficient `format string compilation API
+  <https://fmt.dev/dev/api.html#compile-api>`_:
+
+  .. code:: c++
+
+     #include <fmt/compile.h>
+
+     // Converts 42 into std::string using the most efficient method and no
+     // runtime format string processing.
+     std::string s = fmt::format(FMT_COMPILE("{}"), 42);
+
+  The old ``fmt::compile`` API is now deprecated.
+
+* Optimized integer formatting: ``format_to`` with format string compilation
+  and a stack-allocated buffer is now `faster than to_chars on both
+  libc++ and libstdc++
+  <http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_.
+
+* Optimized handling of small format strings. For example,
+
+  .. code:: c++
+
+      fmt::format("Result: {}: ({},{},{},{})", str1, str2, str3, str4, str5)
+
+  is now ~40% faster (`#1685 <https://github.com/fmtlib/fmt/issues/1685>`_).
+
+* Applied extern templates to improve compile times when using the core API
+  and ``fmt/format.h`` (`#1452 <https://github.com/fmtlib/fmt/issues/1452>`_).
+  For example, on macOS with clang the compile time of a test translation unit
+  dropped from 2.3s to 0.3s with ``-O2`` and from 0.6s to 0.3s with the default
+  settings (``-O0``).
+
+  Before (``-O2``)::
+
+    % time c++ -c test.cc -I include -std=c++17 -O2
+    c++ -c test.cc -I include -std=c++17 -O2  2.22s user 0.08s system 99% cpu 2.311 total
+
+  After (``-O2``)::
+
+    % time c++ -c test.cc -I include -std=c++17 -O2
+    c++ -c test.cc -I include -std=c++17 -O2  0.26s user 0.04s system 98% cpu 0.303 total
+
+  Before (default)::
+
+    % time c++ -c test.cc -I include -std=c++17
+    c++ -c test.cc -I include -std=c++17  0.53s user 0.06s system 98% cpu 0.601 total
+
+  After (default)::
+
+    % time c++ -c test.cc -I include -std=c++17
+    c++ -c test.cc -I include -std=c++17  0.24s user 0.06s system 98% cpu 0.301 total
+
+  It is still recommended to use ``fmt/core.h`` instead of ``fmt/format.h`` but
+  the compile time difference is now smaller. Thanks
+  `@alex3d <https://github.com/alex3d>`_ for the suggestion.
+
+* Named arguments are now stored on stack (no dynamic memory allocations) and
+  the compiled code is more compact and efficient. For example
+
+  .. code:: c++
+
+     #include <fmt/core.h>
+
+     int main() {
+       fmt::print("The answer is {answer}\n", fmt::arg("answer", 42));
+     }
+
+  compiles to just (`godbolt <https://godbolt.org/z/NcfEp_>`__)
+
+  .. code:: asm
+
+      .LC0:
+              .string "answer"
+      .LC1:
+              .string "The answer is {answer}\n"
+      main:
+              sub     rsp, 56
+              mov     edi, OFFSET FLAT:.LC1
+              mov     esi, 23
+              movabs  rdx, 4611686018427387905
+              lea     rax, [rsp+32]
+              lea     rcx, [rsp+16]
+              mov     QWORD PTR [rsp+8], 1
+              mov     QWORD PTR [rsp], rax
+              mov     DWORD PTR [rsp+16], 42
+              mov     QWORD PTR [rsp+32], OFFSET FLAT:.LC0
+              mov     DWORD PTR [rsp+40], 0
+              call    fmt::v6::vprint(fmt::v6::basic_string_view<char>,
+                                      fmt::v6::format_args)
+              xor     eax, eax
+              add     rsp, 56
+              ret
+
+          .L.str.1:
+                  .asciz  "answer"
+
+* Implemented compile-time checks for dynamic width and precision
+  (`#1614 <https://github.com/fmtlib/fmt/issues/1614>`_):
+
+  .. code:: c++
+
+     #include <fmt/format.h>
+
+     int main() {
+       fmt::print(FMT_STRING("{0:{1}}"), 42);
+     }
+
+  now gives a compilation error because argument 1 doesn't exist::
+
+    In file included from test.cc:1:
+    include/fmt/format.h:2726:27: error: constexpr variable 'invalid_format' must be
+    initialized by a constant expression
+      FMT_CONSTEXPR_DECL bool invalid_format =
+                              ^
+    ...
+    include/fmt/core.h:569:26: note: in call to
+    '&checker(s, {}).context_->on_error(&"argument not found"[0])'
+        if (id >= num_args_) on_error("argument not found");
+                            ^
+
+* Added sentinel support to ``fmt::join``
+  (`#1689 <https://github.com/fmtlib/fmt/pull/1689>`_)
+
+  .. code:: c++
+
+    struct zstring_sentinel {};
+    bool operator==(const char* p, zstring_sentinel) { return *p == '\0'; }
+    bool operator!=(const char* p, zstring_sentinel) { return *p != '\0'; }
+
+    struct zstring {
+      const char* p;
+      const char* begin() const { return p; }
+      zstring_sentinel end() const { return {}; }
+    };
+
+    auto s = fmt::format("{}", fmt::join(zstring{"hello"}, "_"));
+    // s == "h_e_l_l_o"
+
+  Thanks `@BRevzin (Barry Revzin) <https://github.com/BRevzin>`_.
+
+* Added support for named args, ``clear`` and ``reserve`` to
+  ``dynamic_format_arg_store``
+  (`#1655 <https://github.com/fmtlib/fmt/issues/1655>`_,
+  `#1663 <https://github.com/fmtlib/fmt/pull/1663>`_,
+  `#1674 <https://github.com/fmtlib/fmt/pull/1674>`_,
+  `#1677 <https://github.com/fmtlib/fmt/pull/1677>`_).
+  Thanks `@vsolontsov-ll (Vladimir Solontsov)
+  <https://github.com/vsolontsov-ll>`_.
+
+* Added support for the ``'c'`` format specifier to integral types for
+  compatibility with ``std::format``
+  (`#1652 <https://github.com/fmtlib/fmt/issues/1652>`_).
+
+* Replaced the ``'n'`` format specifier with ``'L'`` for compatibility with
+  ``std::format`` (`#1624 <https://github.com/fmtlib/fmt/issues/1624>`_).
+  The ``'n'`` specifier can be enabled via the ``FMT_DEPRECATED_N_SPECIFIER``
+  macro.
+
+* The ``'='`` format specifier is now disabled by default for compatibility with
+  ``std::format``. It can be enabled via the ``FMT_DEPRECATED_NUMERIC_ALIGN``
+  macro.
+
+* Removed the following deprecated APIs:
+
+  * ``FMT_STRING_ALIAS`` and ``fmt`` macros - replaced by ``FMT_STRING``
+  * ``fmt::basic_string_view::char_type`` - replaced by
+    ``fmt::basic_string_view::value_type``
+  * ``convert_to_int``
+  * ``format_arg_store::types``
+  * ``*parse_context`` - replaced by ``*format_parse_context``
+  * ``FMT_DEPRECATED_INCLUDE_OS``
+  * ``FMT_DEPRECATED_PERCENT`` - incompatible with ``std::format``
+  * ``*writer`` - replaced by compiled format API
+
+* Renamed the ``internal`` namespace to ``detail``
+  (`#1538 <https://github.com/fmtlib/fmt/issues/1538>`_). The former is still
+  provided as an alias if the ``FMT_USE_INTERNAL`` macro is defined.
+
+* Improved compatibility between ``fmt::printf`` with the standard specs
+  (`#1595 <https://github.com/fmtlib/fmt/issues/1595>`_,
+  `#1682 <https://github.com/fmtlib/fmt/pull/1682>`_,
+  `#1683 <https://github.com/fmtlib/fmt/pull/1683>`_,
+  `#1687 <https://github.com/fmtlib/fmt/pull/1687>`_,
+  `#1699 <https://github.com/fmtlib/fmt/pull/1699>`_).
+  Thanks `@rimathia <https://github.com/rimathia>`_.
+
+* Fixed handling of ``operator<<`` overloads that use ``copyfmt``
+  (`#1666 <https://github.com/fmtlib/fmt/issues/1666>`_).
+
+* Added the ``FMT_OS`` CMake option to control inclusion of OS-specific APIs
+  in the fmt target. This can be useful for embedded platforms
+  (`#1654 <https://github.com/fmtlib/fmt/issues/1654>`_,
+  `#1656 <https://github.com/fmtlib/fmt/pull/1656>`_).
+  Thanks `@kwesolowski (Krzysztof Wesolowski)
+  <https://github.com/kwesolowski>`_.
+
+* Replaced ``FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION`` with the ``FMT_FUZZ``
+  macro to prevent interferring with fuzzing of projects using {fmt}
+  (`#1650 <https://github.com/fmtlib/fmt/pull/1650>`_).
+  Thanks `@asraa (Asra Ali) <https://github.com/asraa>`_.
+
+* Fixed compatibility with emscripten
+  (`#1636 <https://github.com/fmtlib/fmt/issues/1636>`_,
+  `#1637 <https://github.com/fmtlib/fmt/pull/1637>`_).
+  Thanks `@ArthurSonzogni (Arthur Sonzogni)
+  <https://github.com/ArthurSonzogni>`_.
+
+* Improved documentation
+  (`#704 <https://github.com/fmtlib/fmt/issues/704>`_,
+  `#1643 <https://github.com/fmtlib/fmt/pull/1643>`_,
+  `#1660 <https://github.com/fmtlib/fmt/pull/1660>`_,
+  `#1681 <https://github.com/fmtlib/fmt/pull/1681>`_,
+  `#1691 <https://github.com/fmtlib/fmt/pull/1691>`_,
+  `#1706 <https://github.com/fmtlib/fmt/pull/1706>`_,
+  `#1714 <https://github.com/fmtlib/fmt/pull/1714>`_,
+  `#1721 <https://github.com/fmtlib/fmt/pull/1721>`_,
+  `#1739 <https://github.com/fmtlib/fmt/pull/1739>`_,
+  `#1740 <https://github.com/fmtlib/fmt/pull/1740>`_,
+  `#1741 <https://github.com/fmtlib/fmt/pull/1741>`_,
+  `#1751 <https://github.com/fmtlib/fmt/pull/1751>`_).
+  Thanks `@senior7515 (Alexander Gallego) <https://github.com/senior7515>`_,
+  `@lsr0 (Lindsay Roberts) <https://github.com/lsr0>`_,
+  `@puetzk (Kevin Puetz) <https://github.com/puetzk>`_,
+  `@fpelliccioni (Fernando Pelliccioni) <https://github.com/fpelliccioni>`_,
+  Alexey Kuzmenko, `@jelly (jelle van der Waa) <https://github.com/jelly>`_,
+  `@claremacrae (Clare Macrae) <https://github.com/claremacrae>`_,
+  `@jiapengwen (文佳鹏) <https://github.com/jiapengwen>`_,
+  `@gsjaardema (Greg Sjaardema) <https://github.com/gsjaardema>`_,
+  `@alexey-milovidov <https://github.com/alexey-milovidov>`_.
+
+* Implemented various build configuration fixes and improvements
+  (`#1603 <https://github.com/fmtlib/fmt/pull/1603>`_,
+  `#1657 <https://github.com/fmtlib/fmt/pull/1657>`_,
+  `#1702 <https://github.com/fmtlib/fmt/pull/1702>`_,
+  `#1728 <https://github.com/fmtlib/fmt/pull/1728>`_).
+  Thanks `@scramsby (Scott Ramsby) <https://github.com/scramsby>`_,
+  `@jtojnar (Jan Tojnar) <https://github.com/jtojnar>`_,
+  `@orivej (Orivej Desh) <https://github.com/orivej>`_,
+  `@flagarde <https://github.com/flagarde>`_.
+
+* Fixed various warnings and compilation issues
+  (`#1616 <https://github.com/fmtlib/fmt/pull/1616>`_,
+  `#1620 <https://github.com/fmtlib/fmt/issues/1620>`_,
+  `#1622 <https://github.com/fmtlib/fmt/issues/1622>`_,
+  `#1625 <https://github.com/fmtlib/fmt/issues/1625>`_,
+  `#1627 <https://github.com/fmtlib/fmt/pull/1627>`_,
+  `#1628 <https://github.com/fmtlib/fmt/issues/1628>`_,
+  `#1629 <https://github.com/fmtlib/fmt/pull/1629>`_,
+  `#1631 <https://github.com/fmtlib/fmt/issues/1631>`_,
+  `#1633 <https://github.com/fmtlib/fmt/pull/1633>`_,
+  `#1649 <https://github.com/fmtlib/fmt/pull/1649>`_,
+  `#1658 <https://github.com/fmtlib/fmt/issues/1658>`_,
+  `#1661 <https://github.com/fmtlib/fmt/pull/1661>`_,
+  `#1667 <https://github.com/fmtlib/fmt/pull/1667>`_,
+  `#1668 <https://github.com/fmtlib/fmt/issues/1668>`_,
+  `#1669 <https://github.com/fmtlib/fmt/pull/1669>`_,
+  `#1692 <https://github.com/fmtlib/fmt/issues/1692>`_,
+  `#1696 <https://github.com/fmtlib/fmt/pull/1696>`_,
+  `#1697 <https://github.com/fmtlib/fmt/pull/1697>`_,
+  `#1707 <https://github.com/fmtlib/fmt/issues/1707>`_,
+  `#1712 <https://github.com/fmtlib/fmt/pull/1712>`_,
+  `#1716 <https://github.com/fmtlib/fmt/pull/1716>`_,
+  `#1722 <https://github.com/fmtlib/fmt/pull/1722>`_,
+  `#1724 <https://github.com/fmtlib/fmt/issues/1724>`_,
+  `#1729 <https://github.com/fmtlib/fmt/pull/1729>`_,
+  `#1738 <https://github.com/fmtlib/fmt/pull/1738>`_,
+  `#1742 <https://github.com/fmtlib/fmt/issues/1742>`_,
+  `#1743 <https://github.com/fmtlib/fmt/issues/1743>`_,
+  `#1744 <https://github.com/fmtlib/fmt/pull/1744>`_,
+  `#1747 <https://github.com/fmtlib/fmt/issues/1747>`_,
+  `#1750 <https://github.com/fmtlib/fmt/pull/1750>`_).
+  Thanks `@gsjaardema (Greg Sjaardema) <https://github.com/gsjaardema>`_,
+  `@gabime (Gabi Melman) <https://github.com/gabime>`_,
+  `@johnor (Johan) <https://github.com/johnor>`_,
+  `@Kurkin (Dmitry Kurkin) <https://github.com/Kurkin>`_,
+  `@invexed (James Beach) <https://github.com/invexed>`_,
+  `@peterbell10 <https://github.com/peterbell10>`_,
+  `@daixtrose (Markus Werle) <https://github.com/daixtrose>`_,
+  `@petrutlucian94 (Lucian Petrut) <https://github.com/petrutlucian94>`_,
+  `@Neargye (Daniil Goncharov) <https://github.com/Neargye>`_,
+  `@ambitslix (Attila M. Szilagyi) <https://github.com/ambitslix>`_,
+  `@gabime (Gabi Melman) <https://github.com/gabime>`_,
+  `@erthink (Leonid Yuriev) <https://github.com/erthink>`_,
+  `@tohammer (Tobias Hammer) <https://github.com/tohammer>`_,
+  `@0x8000-0000 (Florin Iucha) <https://github.com/0x8000-0000>`_.
+
+6.2.1 - 2020-05-09
+------------------
+
+* Fixed ostream support in ``sprintf``
+  (`#1631 <https://github.com/fmtlib/fmt/issues/1631>`_).
+
+* Fixed type detection when using implicit conversion to ``string_view`` and
+  ostream ``operator<<`` inconsistently
+  (`#1662 <https://github.com/fmtlib/fmt/issues/1662>`_).
+
 6.2.0 - 2020-04-05
 ------------------
 
@@ -24,7 +370,7 @@
 
   if ``S`` is not formattable.
 
-* Reduced library size by ~10%.
+* Reduced the library size by ~10%.
 
 * Always print decimal point if ``#`` is specified
   (`#1476 <https://github.com/fmtlib/fmt/issues/1476>`_,
@@ -587,16 +933,16 @@
      #include <fmt/compile.h>
 
      auto f = fmt::compile<int>("{}");
-     std::string s = fmt::format(f, 42); // can be called multiple times to format
-                                         // different values
+     std::string s = fmt::format(f, 42); // can be called multiple times to
+                                         // format different values
      // s == "42"
 
   It moves the cost of parsing a format string outside of the format function
   which can be beneficial when identically formatting many objects of the same
   types. Thanks `@stryku (Mateusz Janek) <https://github.com/stryku>`_.
 
-* Added the ``%`` format specifier that formats floating-point values as
-  percentages (`#1060 <https://github.com/fmtlib/fmt/pull/1060>`_,
+* Added experimental ``%`` format specifier that formats floating-point values
+  as percentages (`#1060 <https://github.com/fmtlib/fmt/pull/1060>`_,
   `#1069 <https://github.com/fmtlib/fmt/pull/1069>`_,
   `#1071 <https://github.com/fmtlib/fmt/pull/1071>`_):
 
diff --git a/README.rst b/README.rst
index af9f9252..722a65eb 100644
--- a/README.rst
+++ b/README.rst
@@ -9,7 +9,9 @@
 
 .. image:: https://oss-fuzz-build-logs.storage.googleapis.com/badges/libfmt.svg
    :alt: fmt is continuously fuzzed att oss-fuzz
-   :target: https://bugs.chromium.org/p/oss-fuzz/issues/list?colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20Summary&q=proj%3Dlibfmt&can=1
+   :target: https://bugs.chromium.org/p/oss-fuzz/issues/list?\
+            colspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20\
+            Summary&q=proj%3Dlibfmt&can=1
 
 .. image:: https://img.shields.io/badge/stackoverflow-fmt-blue.svg
    :alt: Ask questions at StackOverflow with the tag fmt
@@ -20,42 +22,46 @@ It can be used as a safe and fast alternative to (s)printf and iostreams.
 
 `Documentation <https://fmt.dev/latest/>`__
 
-Q&A: ask questions on `StackOverflow with the tag fmt <https://stackoverflow.com/questions/tagged/fmt>`_.
+Q&A: ask questions on `StackOverflow with the tag fmt
+<https://stackoverflow.com/questions/tagged/fmt>`_.
 
 Features
 --------
 
-* Replacement-based `format API <https://fmt.dev/dev/api.html>`_ with
-  positional arguments for localization.
+* Simple `format API <https://fmt.dev/dev/api.html>`_ with positional arguments
+  for localization
+* Implementation of `C++20 std::format
+  <https://en.cppreference.com/w/cpp/utility/format>`__
 * `Format string syntax <https://fmt.dev/dev/syntax.html>`_ similar to the one
-  of `str.format <https://docs.python.org/3/library/stdtypes.html#str.format>`_
-  in Python.
+  of Python's
+  `format <https://docs.python.org/3/library/stdtypes.html#str.format>`_
 * Safe `printf implementation
   <https://fmt.dev/latest/api.html#printf-formatting>`_ including
-  the POSIX extension for positional arguments.
-* Implementation of `C++20 std::format <https://en.cppreference.com/w/cpp/utility/format>`__.
-* Support for user-defined types.
+  the POSIX extension for positional arguments
+* Extensibility: support for user-defined types
 * High performance: faster than common standard library implementations of
-  `printf <https://en.cppreference.com/w/cpp/io/c/fprintf>`_ and
-  iostreams. See `Speed tests`_ and `Fast integer to string conversion in C++
-  <http://zverovich.net/2013/09/07/integer-to-string-conversion-in-cplusplus.html>`_.
+  `printf <https://en.cppreference.com/w/cpp/io/c/fprintf>`_,
+  iostreams, ``to_string`` and ``to_chars``, see `Speed tests`_ and
+  `Converting a hundred million integers to strings per second
+  <http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_
 * Small code size both in terms of source code (the minimum configuration
   consists of just three header files, ``core.h``, ``format.h`` and
-  ``format-inl.h``) and compiled code. See `Compile time and code bloat`_.
+  ``format-inl.h``) and compiled code. See `Compile time and code bloat`_
 * Reliability: the library has an extensive set of `unit tests
-  <https://github.com/fmtlib/fmt/tree/master/test>`_ and is continuously fuzzed.
+  <https://github.com/fmtlib/fmt/tree/master/test>`_ and is continuously fuzzed
 * Safety: the library is fully type safe, errors in format strings can be
   reported at compile time, automatic memory management prevents buffer overflow
-  errors.
+  errors
 * Ease of use: small self-contained code base, no external dependencies,
   permissive MIT `license
   <https://github.com/fmtlib/fmt/blob/master/LICENSE.rst>`_
 * `Portability <https://fmt.dev/latest/index.html#portability>`_ with
-  consistent output across platforms and support for older compilers.
+  consistent output across platforms and support for older compilers
 * Clean warning-free codebase even on high warning levels
-  (``-Wall -Wextra -pedantic``).
-* Support for wide strings.
-* Optional header-only configuration enabled with the ``FMT_HEADER_ONLY`` macro.
+  (``-Wall -Wextra -pedantic``)
+* Locale-independence by default
+* Support for wide strings
+* Optional header-only configuration enabled with the ``FMT_HEADER_ONLY`` macro
 
 See the `documentation <https://fmt.dev/latest/>`_ for more details.
 
@@ -66,37 +72,49 @@ Print ``Hello, world!`` to ``stdout``:
 
 .. code:: c++
 
-    fmt::print("Hello, {}!", "world");  // Python-like format string syntax
-    fmt::printf("Hello, %s!", "world"); // printf format string syntax
+    #include <fmt/core.h>
+    
+    int main() {
+      fmt::print("Hello, world!\n");
+    }
 
-Format a string and use positional arguments:
+Format a string:
+
+.. code:: c++
+
+    std::string s = fmt::format("The answer is {}.", 42);
+    // s == "The answer is 42."
+
+Format a string using positional arguments:
 
 .. code:: c++
 
     std::string s = fmt::format("I'd rather be {1} than {0}.", "right", "happy");
     // s == "I'd rather be happy than right."
 
+Print a chrono duration:
+
+.. code:: c++
+
+    #include <fmt/chrono.h>
+
+    int main() {
+      using namespace std::chrono_literals;
+      fmt::print("Elapsed time: {}", 42ms);
+    }
+
+prints "Elapsed time: 42ms".
+
 Check a format string at compile time:
 
 .. code:: c++
 
     // test.cc
     #include <fmt/format.h>
-    std::string s = format(FMT_STRING("{2}"), 42);
+    std::string s = format(FMT_STRING("{:d}"), "hello");
 
-.. code::
-
-    $ c++ -Iinclude -std=c++14 test.cc
-    ...
-    test.cc:4:17: note: in instantiation of function template specialization 'fmt::v5::format<S, int>' requested here
-    std::string s = format(FMT_STRING("{2}"), 42);
-                    ^
-    include/fmt/core.h:778:19: note: non-constexpr function 'on_error' cannot be used in a constant expression
-        ErrorHandler::on_error(message);
-                      ^
-    include/fmt/format.h:2226:16: note: in call to '&checker.context_->on_error(&"argument index out of range"[0])'
-          context_.on_error("argument index out of range");
-                   ^
+gives a compile-time error because ``d`` is an invalid format specifier for a
+string.
 
 Use {fmt} as a safe portable replacement for ``itoa``
 (`godbolt <https://godbolt.org/g/NXmpU4>`_):
@@ -113,7 +131,7 @@ Format objects of user-defined types via a simple `extension API
 
 .. code:: c++
 
-    #include "fmt/format.h"
+    #include <fmt/format.h>
 
     struct date {
       int year, month, day;
@@ -174,15 +192,15 @@ Folly Format      folly::format   2.23
 {fmt} is the fastest of the benchmarked methods, ~35% faster than ``printf``.
 
 The above results were generated by building ``tinyformat_test.cpp`` on macOS
-10.14.6 with ``clang++ -O3 -DSPEED_TEST -DHAVE_FORMAT``, and taking the best of
-three runs. In the test, the format string ``"%0.10f:%04d:%+g:%s:%p:%c:%%\n"``
+10.14.6 with ``clang++ -O3 -DNDEBUG -DSPEED_TEST -DHAVE_FORMAT``, and taking the
+best of three runs. In the test, the format string ``"%0.10f:%04d:%+g:%s:%p:%c:%%\n"``
 or equivalent is filled 2,000,000 times with output sent to ``/dev/null``; for
 further details refer to the `source
 <https://github.com/fmtlib/format-benchmark/blob/master/tinyformat_test.cpp>`_.
 
-{fmt} is 10x faster than ``std::ostringstream`` and ``sprintf`` on floating-point
-formatting (`dtoa-benchmark <https://github.com/fmtlib/dtoa-benchmark>`_)
-and as fast as `double-conversion <https://github.com/google/double-conversion>`_:
+{fmt} is up to 10x faster than ``std::ostringstream`` and ``sprintf`` on
+floating-point formatting (`dtoa-benchmark <https://github.com/fmtlib/dtoa-benchmark>`_)
+and faster than `double-conversion <https://github.com/google/double-conversion>`_:
 
 .. image:: https://user-images.githubusercontent.com/576385/69767160-cdaca400-112f-11ea-9fc5-347c9f83caad.png
    :target: https://fmt.dev/unknown_mac64_clang10.0.html
@@ -264,12 +282,15 @@ or the bloat test::
 Projects using this library
 ---------------------------
 
-* `0 A.D. <https://play0ad.com/>`_: A free, open-source, cross-platform real-time
-  strategy game
+* `0 A.D. <https://play0ad.com/>`_: A free, open-source, cross-platform
+  real-time strategy game
 
 * `AMPL/MP <https://github.com/ampl/mp>`_:
   An open-source library for mathematical programming
-  
+
+* `Aseprite <https://github.com/aseprite/aseprite>`_:
+  Animated sprite editor & pixel art tool 
+
 * `AvioBook <https://www.aviobook.aero/en>`_: A comprehensive aircraft
   operations suite
   
@@ -279,9 +300,21 @@ Projects using this library
 
 * `ccache <https://ccache.dev/>`_: A compiler cache
 
+* `ClickHouse <https://github.com/ClickHouse/ClickHouse>`_: analytical database management system
+
 * `CUAUV <http://cuauv.org/>`_: Cornell University's autonomous underwater
   vehicle
 
+* `Drake <https://drake.mit.edu/>`_: A planning, control, and analysis toolbox
+  for nonlinear dynamical systems (MIT)
+
+* `Envoy <https://lyft.github.io/envoy/>`_: C++ L7 proxy and communication bus
+  (Lyft)
+
+* `FiveM <https://fivem.net/>`_: a modification framework for GTA V
+
+* `Folly <https://github.com/facebook/folly>`_: Facebook open-source library
+
 * `HarpyWar/pvpgn <https://github.com/pvpgn/pvpgn-server>`_:
   Player vs Player Gaming Network with tweaks
 
@@ -291,27 +324,25 @@ Projects using this library
 
 * `Kodi <https://kodi.tv/>`_ (formerly xbmc): Home theater software
 
-* `Lifeline <https://github.com/peter-clark/lifeline>`_: A 2D game
+* `Knuth <https://kth.cash/>`_: High-performance Bitcoin full-node
 
-* `Drake <https://drake.mit.edu/>`_: A planning, control, and analysis toolbox
-  for nonlinear dynamical systems (MIT)
-
-* `Envoy <https://lyft.github.io/envoy/>`_: C++ L7 proxy and communication bus
-  (Lyft)
-
-* `FiveM <https://fivem.net/>`_: a modification framework for GTA V
+* `Microsoft Verona <https://github.com/microsoft/verona>`_:
+  Research programming language for concurrent ownership
 
 * `MongoDB <https://mongodb.com/>`_: Distributed document database
 
 * `MongoDB Smasher <https://github.com/duckie/mongo_smasher>`_: A small tool to
   generate randomized datasets
 
-* `OpenSpace <https://openspaceproject.com/>`_: An open-source astrovisualization
-  framework
+* `OpenSpace <https://openspaceproject.com/>`_: An open-source
+  astrovisualization framework
 
 * `PenUltima Online (POL) <https://www.polserver.com/>`_:
   An MMO server, compatible with most Ultima Online clients
 
+* `PyTorch <https://github.com/pytorch/pytorch>`_: An open-source machine
+  learning library
+
 * `quasardb <https://www.quasardb.net/>`_: A distributed, high-performance,
   associative database
 
@@ -320,13 +351,14 @@ Projects using this library
 * `redis-cerberus <https://github.com/HunanTV/redis-cerberus>`_: A Redis cluster
   proxy
 
+* `redpanda <https://vectorized.io/redpanda>`_: A 10x faster Kafka® replacement
+  for mission critical systems written in C++
+
 * `rpclib <http://rpclib.net/>`_: A modern C++ msgpack-RPC server and client
   library
 
-* `Saddy <https://github.com/mamontov-cpp/saddy-graphics-engine-2d>`_:
-  Small crossplatform 2D graphic engine
-
-* `Salesforce Analytics Cloud <https://www.salesforce.com/analytics-cloud/overview/>`_:
+* `Salesforce Analytics Cloud
+  <https://www.salesforce.com/analytics-cloud/overview/>`_:
   Business intelligence software
 
 * `Scylla <https://www.scylladb.com/>`_: A Cassandra-compatible NoSQL data store
@@ -344,6 +376,9 @@ Projects using this library
 * `TrinityCore <https://github.com/TrinityCore/TrinityCore>`_: Open-source
   MMORPG framework
 
+* `Windows Terminal <https://github.com/microsoft/terminal>`_: The new Windows
+  Terminal
+
 `More... <https://github.com/search?q=fmtlib&type=Code>`_
 
 If you are aware of other projects using this library, please let me know
@@ -407,8 +442,8 @@ Format also has excessive build times and severe code bloat issues (see
 FastFormat
 ~~~~~~~~~~
 
-This is an interesting library which is fast, safe and has positional
-arguments. However it has significant limitations, citing its author:
+This is an interesting library which is fast, safe and has positional arguments.
+However, it has significant limitations, citing its author:
 
     Three features that have no hope of being accommodated within the
     current design are:
@@ -417,8 +452,8 @@ arguments. However it has significant limitations, citing its author:
     * Octal/hexadecimal encoding
     * Runtime width/alignment specification
 
-It is also quite big and has a heavy dependency, STLSoft, which might be
-too restrictive for using it in some projects.
+It is also quite big and has a heavy dependency, STLSoft, which might be too
+restrictive for using it in some projects.
 
 Boost Spirit.Karma
 ~~~~~~~~~~~~~~~~~~
@@ -426,32 +461,9 @@ Boost Spirit.Karma
 This is not really a formatting library but I decided to include it here for
 completeness. As iostreams, it suffers from the problem of mixing verbatim text
 with arguments. The library is pretty fast, but slower on integer formatting
-than ``fmt::format_int`` on Karma's own benchmark,
-see `Fast integer to string conversion in C++
-<http://zverovich.net/2013/09/07/integer-to-string-conversion-in-cplusplus.html>`_.
-
-FAQ
----
-
-Q: how can I capture formatting arguments and format them later?
-
-A: use ``std::tuple``:
-
-.. code:: c++
-
-   template <typename... Args>
-   auto capture(const Args&... args) {
-     return std::make_tuple(args...);
-   }
-
-   auto print_message = [](const auto&... args) {
-     fmt::print(args...);
-   };
-
-   // Capture and store arguments:
-   auto args = capture("{} {}", 42, "foo");
-   // Do formatting:
-   std::apply(print_message, args);
+than ``fmt::format_to`` with format string compilation on Karma's own benchmark,
+see `Converting a hundred million integers to strings per second
+<http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html>`_.
 
 License
 -------
@@ -459,18 +471,19 @@ License
 {fmt} is distributed under the MIT `license
 <https://github.com/fmtlib/fmt/blob/master/LICENSE.rst>`_.
 
-The `Format String Syntax
-<https://fmt.dev/latest/syntax.html>`_
-section in the documentation is based on the one from Python `string module
-documentation <https://docs.python.org/3/library/string.html#module-string>`_
-adapted for the current library. For this reason the documentation is
-distributed under the Python Software Foundation license available in
-`doc/python-license.txt
-<https://raw.github.com/fmtlib/fmt/master/doc/python-license.txt>`_.
-It only applies if you distribute the documentation of fmt.
+Documentation License
+---------------------
 
-Acknowledgments
----------------
+The `Format String Syntax <https://fmt.dev/latest/syntax.html>`_
+section in the documentation is based on the one from Python `string module
+documentation <https://docs.python.org/3/library/string.html#module-string>`_.
+For this reason the documentation is distributed under the Python Software
+Foundation license available in `doc/python-license.txt
+<https://raw.github.com/fmtlib/fmt/master/doc/python-license.txt>`_.
+It only applies if you distribute the documentation of {fmt}.
+
+Maintainers
+-----------
 
 The {fmt} library is maintained by Victor Zverovich (`vitaut
 <https://github.com/vitaut>`_) and Jonathan Müller (`foonathan
@@ -479,23 +492,3 @@ See `Contributors <https://github.com/fmtlib/fmt/graphs/contributors>`_ and
 `Releases <https://github.com/fmtlib/fmt/releases>`_ for some of the names.
 Let us know if your contribution is not listed or mentioned incorrectly and
 we'll make it right.
-
-The benchmark section of this readme file and the performance tests are taken
-from the excellent `tinyformat <https://github.com/c42f/tinyformat>`_ library
-written by Chris Foster.  Boost Format library is acknowledged transitively
-since it had some influence on tinyformat.
-Some ideas used in the implementation are borrowed from `Loki
-<http://loki-lib.sourceforge.net/>`_ SafeFormat and `Diagnostic API
-<https://clang.llvm.org/doxygen/classclang_1_1Diagnostic.html>`_ in
-`Clang <https://clang.llvm.org/>`_.
-Format string syntax and the documentation are based on Python's `str.format
-<https://docs.python.org/3/library/stdtypes.html#str.format>`_.
-Thanks `Doug Turnbull <https://github.com/softwaredoug>`_ for his valuable
-comments and contribution to the design of the type-safe API and
-`Gregory Czajkowski <https://github.com/gcflymoto>`_ for implementing binary
-formatting. Thanks `Ruslan Baratov <https://github.com/ruslo>`_ for comprehensive
-`comparison of integer formatting algorithms <https://github.com/ruslo/int-dec-format-tests>`_
-and useful comments regarding performance, `Boris Kaul <https://github.com/localvoid>`_ for
-`C++ counting digits benchmark <https://github.com/localvoid/cxx-benchmark-count-digits>`_.
-Thanks to `CarterLi <https://github.com/CarterLi>`_ for contributing various
-improvements to the code.
diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index f3dae606..108aa71e 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -9,4 +9,5 @@ add_custom_target(doc
   SOURCES api.rst syntax.rst usage.rst build.py conf.py _templates/layout.html)
 
 install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/html/
-        DESTINATION share/doc/fmt OPTIONAL)
+        DESTINATION share/doc/fmt OPTIONAL
+        PATTERN ".doctrees" EXCLUDE)
diff --git a/doc/_templates/layout.html b/doc/_templates/layout.html
index d5f4b70d..333a606c 100644
--- a/doc/_templates/layout.html
+++ b/doc/_templates/layout.html
@@ -6,14 +6,13 @@
 <meta name="author" content="Victor Zverovich">
 <link rel="stylesheet" href="_static/fmt.css">
 {# Google Analytics #}
+<script async src="https://www.googletagmanager.com/gtag/js?id=UA-20116650-4"></script>
 <script>
-  (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
-    (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();
-    a=s.createElement(o),m=s.getElementsByTagName(o)[0];a.async=1;
-    a.src=g;m.parentNode.insertBefore(a,m)
-  })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
-  ga('create', 'UA-20116650-4', 'fmtlib.net');
-  ga('send', 'pageview');
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
+
+  gtag('config', 'UA-20116650-4');
 </script>
 {% endblock %}
 
diff --git a/doc/api.rst b/doc/api.rst
index 4e370252..ca016895 100644
--- a/doc/api.rst
+++ b/doc/api.rst
@@ -9,10 +9,12 @@ The {fmt} library API consists of the following parts:
 * :ref:`fmt/core.h <core-api>`: the core API providing argument handling
   facilities and a lightweight subset of formatting functions
 * :ref:`fmt/format.h <format-api>`: the full format API providing compile-time
-  format string checks, output iterator and user-defined type support
+  format string checks, wide string, output iterator and user-defined type
+  support
 * :ref:`fmt/ranges.h <ranges-api>`: additional formatting support for ranges
   and tuples
 * :ref:`fmt/chrono.h <chrono-api>`: date and time formatting
+* :ref:`fmt/compile.h <compile-api>`: format string compilation
 * :ref:`fmt/ostream.h <ostream-api>`: ``std::ostream`` support
 * :ref:`fmt/printf.h <printf-api>`: ``printf`` formatting
 
@@ -43,7 +45,7 @@ participate in an overload resolution if the latter is not a string.
 .. _format:
 
 .. doxygenfunction:: format(const S&, Args&&...)
-.. doxygenfunction:: vformat(const S&, basic_format_args<buffer_context<Char>>)
+.. doxygenfunction:: vformat(const S&, basic_format_args<buffer_context<type_identity_t<Char>>>)
 
 .. _print:
 
@@ -68,6 +70,9 @@ Argument Lists
 .. doxygenclass:: fmt::format_arg_store
    :members:
 
+.. doxygenclass:: fmt::dynamic_format_arg_store
+   :members:
+
 .. doxygenclass:: fmt::basic_format_args
    :members:
 
@@ -96,7 +101,7 @@ locale::
   #include <locale>
 
   std::locale::global(std::locale("en_US.UTF-8"));
-  auto s = fmt::format("{:n}", 1000000);  // s == "1,000,000"
+  auto s = fmt::format("{:L}", 1000000);  // s == "1,000,000"
 
 .. _format-api:
 
@@ -104,7 +109,7 @@ Format API
 ==========
 
 ``fmt/format.h`` defines the full format API providing compile-time format
-string checks, output iterator and user-defined type support.
+string checks, wide string, output iterator and user-defined type support.
 
 Compile-time Format String Checks
 ---------------------------------
@@ -132,6 +137,7 @@ template and implement ``parse`` and ``format`` methods::
 
     // Parses format specifications of the form ['f' | 'e'].
     constexpr auto parse(format_parse_context& ctx) {
+    // auto parse(format_parse_context &ctx) -> decltype(ctx.begin()) // c++11
       // [ctx.begin(), ctx.end()) is a character range that contains a part of
       // the format string starting from the format specifications to be parsed,
       // e.g. in
@@ -159,6 +165,7 @@ template and implement ``parse`` and ``format`` methods::
     // stored in this formatter.
     template <typename FormatContext>
     auto format(const point& p, FormatContext& ctx) {
+    // auto format(const point &p, FormatContext &ctx) -> decltype(ctx.out()) // c++11
       // ctx.out() is an output iterator to write to.
       return format_to(
           ctx.out(),
@@ -178,8 +185,7 @@ example::
 
   enum class color {red, green, blue};
 
-  template <>
-  struct fmt::formatter<color>: formatter<string_view> {
+  template <> struct fmt::formatter<color>: formatter<string_view> {
     // parse is inherited from formatter<string_view>.
     template <typename FormatContext>
     auto format(color c, FormatContext& ctx) {
@@ -193,6 +199,15 @@ example::
     }
   };
 
+Since ``parse`` is inherited from ``formatter<string_view>`` it will recognize
+all string format specifications, for example
+
+.. code-block:: c++
+
+   fmt::format("{:>10}", color::blue)
+
+will return ``"      blue"``.
+
 You can also write a formatter for a hierarchy of classes::
 
   #include <type_traits>
@@ -229,7 +244,7 @@ Output Iterator Support
 -----------------------
 
 .. doxygenfunction:: fmt::format_to(OutputIt, const S&, Args&&...)
-.. doxygenfunction:: fmt::format_to_n(OutputIt, std::size_t, string_view, Args&&...)
+.. doxygenfunction:: fmt::format_to_n(OutputIt, size_t, const S&, const Args&...)
 .. doxygenstruct:: fmt::format_to_n_result
    :members:
 
@@ -238,9 +253,9 @@ Literal-based API
 
 The following user-defined literals are defined in ``fmt/format.h``.
 
-.. doxygenfunction:: operator""_format(const char *, std::size_t)
+.. doxygenfunction:: operator""_format(const char *, size_t)
 
-.. doxygenfunction:: operator""_a(const char *, std::size_t)
+.. doxygenfunction:: operator""_a(const char *, size_t)
 
 Utilities
 ---------
@@ -259,7 +274,10 @@ Utilities
 
 .. doxygenfunction:: fmt::join(const Range&, string_view)
 
-.. doxygenfunction:: fmt::join(It, It, string_view)
+.. doxygenfunction:: fmt::join(It, Sentinel, string_view)
+
+.. doxygenclass:: fmt::detail::buffer
+   :members:
 
 .. doxygenclass:: fmt::basic_memory_buffer
    :protected-members:
@@ -317,50 +335,6 @@ arguments, the container that stores pointers to them will be allocated using
 the default allocator. Also floating-point formatting falls back on ``sprintf``
 which may do allocations.
 
-Custom Formatting of Built-in Types
------------------------------------
-
-It is possible to change the way arguments are formatted by providing a
-custom argument formatter class::
-
-  using arg_formatter = fmt::arg_formatter<fmt::buffer_range<char>>;
-
-  // A custom argument formatter that formats negative integers as unsigned
-  // with the ``x`` format specifier.
-  class custom_arg_formatter : public arg_formatter {
-   public:
-    custom_arg_formatter(fmt::format_context& ctx,
-                         fmt::format_parse_context* parse_ctx = nullptr,
-                         fmt::format_specs* spec = nullptr)
-      : arg_formatter(ctx, parse_ctx, spec) {}
-
-    using arg_formatter::operator();
-
-    auto operator()(int value) {
-      if (specs() && specs()->type == 'x')
-        return (*this)(static_cast<unsigned>(value)); // convert to unsigned and format
-      return arg_formatter::operator()(value);
-    }
-  };
-
-  std::string custom_vformat(fmt::string_view format_str, fmt::format_args args) {
-    fmt::memory_buffer buffer;
-    // Pass custom argument formatter as a template arg to vformat_to.
-    fmt::vformat_to<custom_arg_formatter>(buffer, format_str, args);
-    return fmt::to_string(buffer);
-  }
-
-  template <typename ...Args>
-  inline std::string custom_format(
-      fmt::string_view format_str, const Args&... args) {
-    return custom_vformat(format_str, fmt::make_format_args(args...));
-  }
-
-  std::string s = custom_format("{:x}", -42); // s == "ffffffd6"
-
-.. doxygenclass:: fmt::arg_formatter
-   :members:
-
 .. _ranges-api:
 
 Ranges and Tuple Formatting
@@ -399,11 +373,26 @@ formatting::
 
   std::time_t t = std::time(nullptr);
   // Prints "The date is 2016-04-29." (with the current date)
-  fmt::print("The date is {:%Y-%m-%d}.", *std::localtime(&t));
+  fmt::print("The date is {:%Y-%m-%d}.", fmt::localtime(t));
 
 The format string syntax is described in the documentation of
 `strftime <http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
 
+.. _compile-api:
+
+Format string compilation
+=========================
+
+``fmt/compile.h`` provides format string compilation support. Format strings
+are parsed at compile time and converted into efficient formatting code. This
+supports arguments of built-in and string types as well as user-defined types
+with ``constexpr`` ``parse`` functions in their ``formatter`` specializations.
+Format string compilation can generate more binary code compared to the default
+API and is only recommended in places where formatting is a performance
+bottleneck.
+
+.. doxygendefine:: FMT_COMPILE
+
 .. _ostream-api:
 
 ``std::ostream`` Support
@@ -448,3 +437,19 @@ argument type doesn't match its format specification.
 .. doxygenfunction:: fprintf(std::basic_ostream<Char>&, const S&, const Args&...)
 
 .. doxygenfunction:: sprintf(const S&, const Args&...)
+
+Compatibility with C++20 ``std::format``
+========================================
+
+{fmt} implements nearly all of the `C++20 formatting library
+<https://en.cppreference.com/w/cpp/utility/format>`_ with the following
+differences:
+
+* Names are defined in the ``fmt`` namespace instead of ``std`` to avoid
+  collisions with standard library implementations.
+* The ``'L'`` format specifier cannot be combined with presentation specifiers
+  yet.
+* Width calculation doesn't use grapheme clusterization. The latter has been
+  implemented in a separate branch but hasn't been integrated yet.
+* Chrono formatting doesn't support C++20 date types since they are not provided
+  by standard library implementations.
diff --git a/doc/build.py b/doc/build.py
index a7bfcf73..06e105aa 100755
--- a/doc/build.py
+++ b/doc/build.py
@@ -6,7 +6,7 @@ import errno, os, shutil, sys, tempfile
 from subprocess import check_call, check_output, CalledProcessError, Popen, PIPE
 from distutils.version import LooseVersion
 
-versions = ['1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0', '5.0.0', '5.1.0', '5.2.0', '5.2.1', '5.3.0', '6.0.0', '6.1.0', '6.1.1', '6.1.2', '6.2.0']
+versions = ['1.0.0', '1.1.0', '2.0.0', '3.0.2', '4.0.0', '4.1.0', '5.0.0', '5.1.0', '5.2.0', '5.2.1', '5.3.0', '6.0.0', '6.1.0', '6.1.1', '6.1.2', '6.2.0', '6.2.1', '7.0.0', '7.0.1', '7.0.2', '7.0.3']
 
 def pip_install(package, commit=None, **kwargs):
   "Install package using pip."
@@ -74,8 +74,8 @@ def build_docs(version='dev', **kwargs):
       GENERATE_MAN      = NO
       GENERATE_RTF      = NO
       CASE_SENSE_NAMES  = NO
-      INPUT             = {0}/core.h {0}/format.h {0}/os.h {0}/ostream.h \
-                          {0}/printf.h {0}/time.h
+      INPUT             = {0}/core.h {0}/compile.h {0}/format.h {0}/os.h \
+                          {0}/ostream.h {0}/printf.h {0}/time.h
       QUIET             = YES
       JAVADOC_AUTOBRIEF = YES
       AUTOLINK_SUPPORT  = NO
diff --git a/doc/index.rst b/doc/index.rst
index d02ab0b0..59dc6652 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -22,7 +22,7 @@ Format API
 ----------
 
 The format API is similar in spirit to the C ``printf`` family of function but
-is safer, simpler and serveral times `faster
+is safer, simpler and several times `faster
 <http://zverovich.net/2013/09/07/integer-to-string-conversion-in-cplusplus.html>`_
 than common standard library implementations.
 The `format string syntax <syntax.html>`_ is similar to the one used by
diff --git a/doc/syntax.rst b/doc/syntax.rst
index bf2f1b6b..8265f702 100644
--- a/doc/syntax.rst
+++ b/doc/syntax.rst
@@ -79,8 +79,8 @@ The general form of a *standard format specifier* is:
    fill: <a character other than '{' or '}'>
    align: "<" | ">" | "^"
    sign: "+" | "-" | " "
-   width: `integer` | "{" `arg_id` "}"
-   precision: `integer` | "{" `arg_id` "}"
+   width: `integer` | "{" [`arg_id`] "}"
+   precision: `integer` | "{" [`arg_id`] "}"
    type: `int_type` | "a" | "A" | "c" | "e" | "E" | "f" | "F" | "g" | "G" | "L" | "p" | "s"
    int_type: "b" | "B" | "d" | "o" | "x" | "X"
 
diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index 421d464a..e70b8053 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -48,7 +48,7 @@ FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
     // From fits in To without any problem.
   } else {
     // From does not always fit in To, resort to a dynamic check.
-    if (from < T::min() || from > T::max()) {
+    if (from < (T::min)() || from > (T::max)()) {
       // outside range.
       ec = 1;
       return {};
@@ -74,7 +74,7 @@ FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
 
   if (F::is_signed && !T::is_signed) {
     // From may be negative, not allowed!
-    if (fmt::internal::is_negative(from)) {
+    if (fmt::detail::is_negative(from)) {
       ec = 1;
       return {};
     }
@@ -84,7 +84,7 @@ FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
       // yes, From always fits in To.
     } else {
       // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
+      if (from > static_cast<From>((T::max)())) {
         ec = 1;
         return {};
       }
@@ -97,7 +97,7 @@ FMT_CONSTEXPR To lossless_integral_conversion(const From from, int& ec) {
       // yes, From always fits in To.
     } else {
       // from may not fit in To, we have to do a dynamic check
-      if (from > static_cast<From>(T::max())) {
+      if (from > static_cast<From>((T::max)())) {
         // outside range.
         ec = 1;
         return {};
@@ -141,7 +141,7 @@ FMT_CONSTEXPR To safe_float_conversion(const From from, int& ec) {
 
   // catch the only happy case
   if (std::isfinite(from)) {
-    if (from >= T::lowest() && from <= T::max()) {
+    if (from >= T::lowest() && from <= (T::max)()) {
       return static_cast<To>(from);
     }
     // not within range.
@@ -195,12 +195,13 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
   }
   // multiply with Factor::num without overflow or underflow
   if (Factor::num != 1) {
-    const auto max1 = internal::max_value<IntermediateRep>() / Factor::num;
+    const auto max1 = detail::max_value<IntermediateRep>() / Factor::num;
     if (count > max1) {
       ec = 1;
       return {};
     }
-    const auto min1 = std::numeric_limits<IntermediateRep>::min() / Factor::num;
+    const auto min1 =
+        (std::numeric_limits<IntermediateRep>::min)() / Factor::num;
     if (count < min1) {
       ec = 1;
       return {};
@@ -269,7 +270,7 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
 
   // multiply with Factor::num without overflow or underflow
   if (Factor::num != 1) {
-    constexpr auto max1 = internal::max_value<IntermediateRep>() /
+    constexpr auto max1 = detail::max_value<IntermediateRep>() /
                           static_cast<IntermediateRep>(Factor::num);
     if (count > max1) {
       ec = 1;
@@ -306,12 +307,12 @@ To safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
 // Usage: f FMT_NOMACRO()
 #define FMT_NOMACRO
 
-namespace internal {
+namespace detail {
 inline null<> localtime_r FMT_NOMACRO(...) { return null<>(); }
 inline null<> localtime_s(...) { return null<>(); }
 inline null<> gmtime_r(...) { return null<>(); }
 inline null<> gmtime_s(...) { return null<>(); }
-}  // namespace internal
+}  // namespace detail
 
 // Thread-safe replacement for std::localtime
 inline std::tm localtime(std::time_t time) {
@@ -322,22 +323,22 @@ inline std::tm localtime(std::time_t time) {
     dispatcher(std::time_t t) : time_(t) {}
 
     bool run() {
-      using namespace fmt::internal;
+      using namespace fmt::detail;
       return handle(localtime_r(&time_, &tm_));
     }
 
     bool handle(std::tm* tm) { return tm != nullptr; }
 
-    bool handle(internal::null<>) {
-      using namespace fmt::internal;
+    bool handle(detail::null<>) {
+      using namespace fmt::detail;
       return fallback(localtime_s(&tm_, &time_));
     }
 
     bool fallback(int res) { return res == 0; }
 
 #if !FMT_MSC_VER
-    bool fallback(internal::null<>) {
-      using namespace fmt::internal;
+    bool fallback(detail::null<>) {
+      using namespace fmt::detail;
       std::tm* tm = std::localtime(&time_);
       if (tm) tm_ = *tm;
       return tm != nullptr;
@@ -359,21 +360,21 @@ inline std::tm gmtime(std::time_t time) {
     dispatcher(std::time_t t) : time_(t) {}
 
     bool run() {
-      using namespace fmt::internal;
+      using namespace fmt::detail;
       return handle(gmtime_r(&time_, &tm_));
     }
 
     bool handle(std::tm* tm) { return tm != nullptr; }
 
-    bool handle(internal::null<>) {
-      using namespace fmt::internal;
+    bool handle(detail::null<>) {
+      using namespace fmt::detail;
       return fallback(gmtime_s(&tm_, &time_));
     }
 
     bool fallback(int res) { return res == 0; }
 
 #if !FMT_MSC_VER
-    bool fallback(internal::null<>) {
+    bool fallback(detail::null<>) {
       std::tm* tm = std::gmtime(&time_);
       if (tm) tm_ = *tm;
       return tm != nullptr;
@@ -386,17 +387,17 @@ inline std::tm gmtime(std::time_t time) {
   return gt.tm_;
 }
 
-namespace internal {
-inline std::size_t strftime(char* str, std::size_t count, const char* format,
-                            const std::tm* time) {
+namespace detail {
+inline size_t strftime(char* str, size_t count, const char* format,
+                       const std::tm* time) {
   return std::strftime(str, count, format, time);
 }
 
-inline std::size_t strftime(wchar_t* str, std::size_t count,
-                            const wchar_t* format, const std::tm* time) {
+inline size_t strftime(wchar_t* str, size_t count, const wchar_t* format,
+                       const std::tm* time) {
   return std::wcsftime(str, count, format, time);
 }
-}  // namespace internal
+}  // namespace detail
 
 template <typename Char> struct formatter<std::tm, Char> {
   template <typename ParseContext>
@@ -405,7 +406,7 @@ template <typename Char> struct formatter<std::tm, Char> {
     if (it != ctx.end() && *it == ':') ++it;
     auto end = it;
     while (end != ctx.end() && *end != '}') ++end;
-    tm_format.reserve(internal::to_unsigned(end - it + 1));
+    tm_format.reserve(detail::to_unsigned(end - it + 1));
     tm_format.append(it, end);
     tm_format.push_back('\0');
     return end;
@@ -414,11 +415,10 @@ template <typename Char> struct formatter<std::tm, Char> {
   template <typename FormatContext>
   auto format(const std::tm& tm, FormatContext& ctx) -> decltype(ctx.out()) {
     basic_memory_buffer<Char> buf;
-    std::size_t start = buf.size();
+    size_t start = buf.size();
     for (;;) {
-      std::size_t size = buf.capacity() - start;
-      std::size_t count =
-          internal::strftime(&buf[start], size, &tm_format[0], &tm);
+      size_t size = buf.capacity() - start;
+      size_t count = detail::strftime(&buf[start], size, &tm_format[0], &tm);
       if (count != 0) {
         buf.resize(start + count);
         break;
@@ -430,7 +430,7 @@ template <typename Char> struct formatter<std::tm, Char> {
         // https://github.com/fmtlib/fmt/issues/367
         break;
       }
-      const std::size_t MIN_GROWTH = 10;
+      const size_t MIN_GROWTH = 10;
       buf.reserve(buf.capacity() + (size > MIN_GROWTH ? size : MIN_GROWTH));
     }
     return std::copy(buf.begin(), buf.end(), ctx.out());
@@ -439,7 +439,7 @@ template <typename Char> struct formatter<std::tm, Char> {
   basic_memory_buffer<Char> tm_format;
 };
 
-namespace internal {
+namespace detail {
 template <typename Period> FMT_CONSTEXPR const char* get_units() {
   return nullptr;
 }
@@ -768,19 +768,25 @@ OutputIt format_duration_value(OutputIt out, Rep val, int precision) {
   return format_to(out, std::is_floating_point<Rep>::value ? fp_f : format,
                    val);
 }
+template <typename Char, typename OutputIt>
+OutputIt copy_unit(string_view unit, OutputIt out, Char) {
+  return std::copy(unit.begin(), unit.end(), out);
+}
+
+template <typename OutputIt>
+OutputIt copy_unit(string_view unit, OutputIt out, wchar_t) {
+  // This works when wchar_t is UTF-32 because units only contain characters
+  // that have the same representation in UTF-16 and UTF-32.
+  utf8_to_utf16 u(unit);
+  return std::copy(u.c_str(), u.c_str() + u.size(), out);
+}
 
 template <typename Char, typename Period, typename OutputIt>
 OutputIt format_duration_unit(OutputIt out) {
-  if (const char* unit = get_units<Period>()) {
-    string_view s(unit);
-    if (const_check(std::is_same<Char, wchar_t>())) {
-      utf8_to_utf16 u(s);
-      return std::copy(u.c_str(), u.c_str() + u.size(), out);
-    }
-    return std::copy(s.begin(), s.end(), out);
-  }
+  if (const char* unit = get_units<Period>())
+    return copy_unit(string_view(unit), out, Char());
   const Char num_f[] = {'[', '{', '}', ']', 's', 0};
-  if (Period::den == 1) return format_to(out, num_f, Period::num);
+  if (const_check(Period::den == 1)) return format_to(out, num_f, Period::num);
   const Char num_def_f[] = {'[', '{', '}', '/', '{', '}', ']', 's', 0};
   return format_to(out, num_def_f, Period::num, Period::den);
 }
@@ -874,9 +880,9 @@ struct chrono_formatter {
     if (isnan(value)) return write_nan();
     uint32_or_64_or_128_t<int> n =
         to_unsigned(to_nonnegative_int(value, max_value<int>()));
-    int num_digits = internal::count_digits(n);
+    int num_digits = detail::count_digits(n);
     if (width > num_digits) out = std::fill_n(out, width - num_digits, '0');
-    out = format_decimal<char_type>(out, n, num_digits);
+    out = format_decimal<char_type>(out, n, num_digits).end;
   }
 
   void write_nan() { std::copy_n("nan", 3, out); }
@@ -1004,14 +1010,14 @@ struct chrono_formatter {
     out = format_duration_unit<char_type, Period>(out);
   }
 };
-}  // namespace internal
+}  // namespace detail
 
 template <typename Rep, typename Period, typename Char>
 struct formatter<std::chrono::duration<Rep, Period>, Char> {
  private:
   basic_format_specs<Char> specs;
   int precision;
-  using arg_ref_type = internal::arg_ref<Char>;
+  using arg_ref_type = detail::arg_ref<Char>;
   arg_ref_type width_ref;
   arg_ref_type precision_ref;
   mutable basic_string_view<Char> format_str;
@@ -1032,7 +1038,7 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
       return arg_ref_type(arg_id);
     }
 
-    FMT_CONSTEXPR arg_ref_type make_arg_ref(internal::auto_id) {
+    FMT_CONSTEXPR arg_ref_type make_arg_ref(detail::auto_id) {
       return arg_ref_type(context.next_arg_id());
     }
 
@@ -1062,17 +1068,17 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
     auto begin = ctx.begin(), end = ctx.end();
     if (begin == end || *begin == '}') return {begin, begin};
     spec_handler handler{*this, ctx, format_str};
-    begin = internal::parse_align(begin, end, handler);
+    begin = detail::parse_align(begin, end, handler);
     if (begin == end) return {begin, begin};
-    begin = internal::parse_width(begin, end, handler);
+    begin = detail::parse_width(begin, end, handler);
     if (begin == end) return {begin, begin};
     if (*begin == '.') {
       if (std::is_floating_point<Rep>::value)
-        begin = internal::parse_precision(begin, end, handler);
+        begin = detail::parse_precision(begin, end, handler);
       else
         handler.on_error("precision not allowed for this argument type");
     }
-    end = parse_chrono_format(begin, end, internal::chrono_format_checker());
+    end = parse_chrono_format(begin, end, detail::chrono_format_checker());
     return {begin, end};
   }
 
@@ -1083,7 +1089,7 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
       -> decltype(ctx.begin()) {
     auto range = do_parse(ctx);
     format_str = basic_string_view<Char>(
-        &*range.begin, internal::to_unsigned(range.end - range.begin));
+        &*range.begin, detail::to_unsigned(range.end - range.begin));
     return range.end;
   }
 
@@ -1094,23 +1100,21 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
     // is not specified.
     basic_memory_buffer<Char> buf;
     auto out = std::back_inserter(buf);
-    using range = internal::output_range<decltype(ctx.out()), Char>;
-    internal::basic_writer<range> w(range(ctx.out()));
-    internal::handle_dynamic_spec<internal::width_checker>(specs.width,
-                                                           width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
-        precision, precision_ref, ctx);
+    detail::handle_dynamic_spec<detail::width_checker>(specs.width, width_ref,
+                                                       ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(precision,
+                                                           precision_ref, ctx);
     if (begin == end || *begin == '}') {
-      out = internal::format_duration_value<Char>(out, d.count(), precision);
-      internal::format_duration_unit<Char, Period>(out);
+      out = detail::format_duration_value<Char>(out, d.count(), precision);
+      detail::format_duration_unit<Char, Period>(out);
     } else {
-      internal::chrono_formatter<FormatContext, decltype(out), Rep, Period> f(
+      detail::chrono_formatter<FormatContext, decltype(out), Rep, Period> f(
           ctx, out, d);
       f.precision = precision;
       parse_chrono_format(begin, end, f);
     }
-    w.write(buf.data(), buf.size(), specs);
-    return w.out();
+    return detail::write(
+        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
   }
 };
 
diff --git a/include/fmt/color.h b/include/fmt/color.h
index 96d9ab6b..b65f892a 100644
--- a/include/fmt/color.h
+++ b/include/fmt/color.h
@@ -198,7 +198,7 @@ struct rgb {
   uint8_t b;
 };
 
-namespace internal {
+namespace detail {
 
 // color is a struct of either a rgb color or a terminal color.
 struct color_type {
@@ -221,7 +221,7 @@ struct color_type {
     uint32_t rgb_color;
   } value;
 };
-}  // namespace internal
+}  // namespace detail
 
 // Experimental text formatting support.
 class text_style {
@@ -298,11 +298,11 @@ class text_style {
   FMT_CONSTEXPR bool has_emphasis() const FMT_NOEXCEPT {
     return static_cast<uint8_t>(ems) != 0;
   }
-  FMT_CONSTEXPR internal::color_type get_foreground() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR detail::color_type get_foreground() const FMT_NOEXCEPT {
     FMT_ASSERT(has_foreground(), "no foreground specified for this style");
     return foreground_color;
   }
-  FMT_CONSTEXPR internal::color_type get_background() const FMT_NOEXCEPT {
+  FMT_CONSTEXPR detail::color_type get_background() const FMT_NOEXCEPT {
     FMT_ASSERT(has_background(), "no background specified for this style");
     return background_color;
   }
@@ -313,7 +313,7 @@ class text_style {
 
  private:
   FMT_CONSTEXPR text_style(bool is_foreground,
-                           internal::color_type text_color) FMT_NOEXCEPT
+                           detail::color_type text_color) FMT_NOEXCEPT
       : set_foreground_color(),
         set_background_color(),
         ems() {
@@ -326,23 +326,23 @@ class text_style {
     }
   }
 
-  friend FMT_CONSTEXPR_DECL text_style fg(internal::color_type foreground)
+  friend FMT_CONSTEXPR_DECL text_style fg(detail::color_type foreground)
       FMT_NOEXCEPT;
-  friend FMT_CONSTEXPR_DECL text_style bg(internal::color_type background)
+  friend FMT_CONSTEXPR_DECL text_style bg(detail::color_type background)
       FMT_NOEXCEPT;
 
-  internal::color_type foreground_color;
-  internal::color_type background_color;
+  detail::color_type foreground_color;
+  detail::color_type background_color;
   bool set_foreground_color;
   bool set_background_color;
   emphasis ems;
 };
 
-FMT_CONSTEXPR text_style fg(internal::color_type foreground) FMT_NOEXCEPT {
+FMT_CONSTEXPR text_style fg(detail::color_type foreground) FMT_NOEXCEPT {
   return text_style(/*is_foreground=*/true, foreground);
 }
 
-FMT_CONSTEXPR text_style bg(internal::color_type background) FMT_NOEXCEPT {
+FMT_CONSTEXPR text_style bg(detail::color_type background) FMT_NOEXCEPT {
   return text_style(/*is_foreground=*/false, background);
 }
 
@@ -350,21 +350,21 @@ FMT_CONSTEXPR text_style operator|(emphasis lhs, emphasis rhs) FMT_NOEXCEPT {
   return text_style(lhs) | rhs;
 }
 
-namespace internal {
+namespace detail {
 
 template <typename Char> struct ansi_color_escape {
-  FMT_CONSTEXPR ansi_color_escape(internal::color_type text_color,
+  FMT_CONSTEXPR ansi_color_escape(detail::color_type text_color,
                                   const char* esc) FMT_NOEXCEPT {
     // If we have a terminal color, we need to output another escape code
     // sequence.
     if (!text_color.is_rgb) {
-      bool is_background = esc == internal::data::background_color;
+      bool is_background = esc == detail::data::background_color;
       uint32_t value = text_color.value.term_color;
       // Background ASCII codes are the same as the foreground ones but with
       // 10 more.
       if (is_background) value += 10u;
 
-      std::size_t index = 0;
+      size_t index = 0;
       buffer[index++] = static_cast<Char>('\x1b');
       buffer[index++] = static_cast<Char>('[');
 
@@ -398,7 +398,7 @@ template <typename Char> struct ansi_color_escape {
     if (em_bits & static_cast<uint8_t>(emphasis::strikethrough))
       em_codes[3] = 9;
 
-    std::size_t index = 0;
+    size_t index = 0;
     for (int i = 0; i < 4; ++i) {
       if (!em_codes[i]) continue;
       buffer[index++] = static_cast<Char>('\x1b');
@@ -429,14 +429,14 @@ template <typename Char> struct ansi_color_escape {
 
 template <typename Char>
 FMT_CONSTEXPR ansi_color_escape<Char> make_foreground_color(
-    internal::color_type foreground) FMT_NOEXCEPT {
-  return ansi_color_escape<Char>(foreground, internal::data::foreground_color);
+    detail::color_type foreground) FMT_NOEXCEPT {
+  return ansi_color_escape<Char>(foreground, detail::data::foreground_color);
 }
 
 template <typename Char>
 FMT_CONSTEXPR ansi_color_escape<Char> make_background_color(
-    internal::color_type background) FMT_NOEXCEPT {
-  return ansi_color_escape<Char>(background, internal::data::background_color);
+    detail::color_type background) FMT_NOEXCEPT {
+  return ansi_color_escape<Char>(background, detail::data::background_color);
 }
 
 template <typename Char>
@@ -455,11 +455,11 @@ inline void fputs<wchar_t>(const wchar_t* chars, FILE* stream) FMT_NOEXCEPT {
 }
 
 template <typename Char> inline void reset_color(FILE* stream) FMT_NOEXCEPT {
-  fputs(internal::data::reset_color, stream);
+  fputs(detail::data::reset_color, stream);
 }
 
 template <> inline void reset_color<wchar_t>(FILE* stream) FMT_NOEXCEPT {
-  fputs(internal::data::wreset_color, stream);
+  fputs(detail::data::wreset_color, stream);
 }
 
 template <typename Char>
@@ -476,33 +476,31 @@ void vformat_to(basic_memory_buffer<Char>& buf, const text_style& ts,
   bool has_style = false;
   if (ts.has_emphasis()) {
     has_style = true;
-    auto emphasis = internal::make_emphasis<Char>(ts.get_emphasis());
+    auto emphasis = detail::make_emphasis<Char>(ts.get_emphasis());
     buf.append(emphasis.begin(), emphasis.end());
   }
   if (ts.has_foreground()) {
     has_style = true;
-    auto foreground =
-        internal::make_foreground_color<Char>(ts.get_foreground());
+    auto foreground = detail::make_foreground_color<Char>(ts.get_foreground());
     buf.append(foreground.begin(), foreground.end());
   }
   if (ts.has_background()) {
     has_style = true;
-    auto background =
-        internal::make_background_color<Char>(ts.get_background());
+    auto background = detail::make_background_color<Char>(ts.get_background());
     buf.append(background.begin(), background.end());
   }
-  internal::vformat_to(buf, format_str, args);
-  if (has_style) internal::reset_color<Char>(buf);
+  detail::vformat_to(buf, format_str, args);
+  if (has_style) detail::reset_color<Char>(buf);
 }
-}  // namespace internal
+}  // namespace detail
 
 template <typename S, typename Char = char_t<S>>
 void vprint(std::FILE* f, const text_style& ts, const S& format,
             basic_format_args<buffer_context<Char>> args) {
   basic_memory_buffer<Char> buf;
-  internal::vformat_to(buf, ts, to_string_view(format), args);
+  detail::vformat_to(buf, ts, to_string_view(format), args);
   buf.push_back(Char(0));
-  internal::fputs(buf.data(), f);
+  detail::fputs(buf.data(), f);
 }
 
 /**
@@ -513,10 +511,10 @@ void vprint(std::FILE* f, const text_style& ts, const S& format,
                "Elapsed time: {0:.2f} seconds", 1.23);
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 void print(std::FILE* f, const text_style& ts, const S& format_str,
            const Args&... args) {
-  internal::check_format_string<Args...>(format_str);
+  detail::check_format_string<Args...>(format_str);
   using context = buffer_context<char_t<S>>;
   format_arg_store<context, Args...> as{args...};
   vprint(f, ts, format_str, basic_format_args<context>(as));
@@ -530,7 +528,7 @@ void print(std::FILE* f, const text_style& ts, const S& format_str,
                "Elapsed time: {0:.2f} seconds", 1.23);
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 void print(const text_style& ts, const S& format_str, const Args&... args) {
   return print(stdout, ts, format_str, args...);
 }
@@ -540,7 +538,7 @@ inline std::basic_string<Char> vformat(
     const text_style& ts, const S& format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buf;
-  internal::vformat_to(buf, ts, to_string_view(format_str), args);
+  detail::vformat_to(buf, ts, to_string_view(format_str), args);
   return fmt::to_string(buf);
 }
 
@@ -560,7 +558,7 @@ template <typename S, typename... Args, typename Char = char_t<S>>
 inline std::basic_string<Char> format(const text_style& ts, const S& format_str,
                                       const Args&... args) {
   return vformat(ts, to_string_view(format_str),
-                 internal::make_args_checked<Args...>(format_str, args...));
+                 detail::make_args_checked<Args...>(format_str, args...));
 }
 
 FMT_END_NAMESPACE
diff --git a/include/fmt/compile.h b/include/fmt/compile.h
index e4b12f34..d7e6449e 100644
--- a/include/fmt/compile.h
+++ b/include/fmt/compile.h
@@ -13,7 +13,33 @@
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
+
+// A compile-time string which is compiled into fast formatting code.
+class compiled_string {};
+
+template <typename S>
+struct is_compiled_string : std::is_base_of<compiled_string, S> {};
+
+/**
+  \rst
+  Converts a string literal *s* into a format string that will be parsed at
+  compile time and converted into efficient formatting code. Requires C++17
+  ``constexpr if`` compiler support.
+
+  **Example**::
+
+    // Converts 42 into std::string using the most efficient method and no
+    // runtime format string processing.
+    std::string s = fmt::format(FMT_COMPILE("{}"), 42);
+  \endrst
+ */
+#define FMT_COMPILE(s) FMT_STRING_IMPL(s, fmt::detail::compiled_string)
+
+template <typename T, typename... Tail>
+const T& first(const T& value, const Tail&...) {
+  return value;
+}
 
 // Part of a compiled format string. It can be either literal text or a
 // replacement field.
@@ -62,13 +88,15 @@ template <typename Char> struct part_counter {
     if (begin != end) ++num_parts;
   }
 
-  FMT_CONSTEXPR void on_arg_id() { ++num_parts; }
-  FMT_CONSTEXPR void on_arg_id(int) { ++num_parts; }
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) { ++num_parts; }
+  FMT_CONSTEXPR int on_arg_id() { return ++num_parts, 0; }
+  FMT_CONSTEXPR int on_arg_id(int) { return ++num_parts, 0; }
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char>) {
+    return ++num_parts, 0;
+  }
 
-  FMT_CONSTEXPR void on_replacement_field(const Char*) {}
+  FMT_CONSTEXPR void on_replacement_field(int, const Char*) {}
 
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin,
+  FMT_CONSTEXPR const Char* on_format_specs(int, const Char* begin,
                                             const Char* end) {
     // Find the matching brace.
     unsigned brace_counter = 0;
@@ -116,25 +144,28 @@ class format_string_compiler : public error_handler {
       handler_(part::make_text({begin, to_unsigned(end - begin)}));
   }
 
-  FMT_CONSTEXPR void on_arg_id() {
+  FMT_CONSTEXPR int on_arg_id() {
     part_ = part::make_arg_index(parse_context_.next_arg_id());
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_arg_id(int id) {
+  FMT_CONSTEXPR int on_arg_id(int id) {
     parse_context_.check_arg_id(id);
     part_ = part::make_arg_index(id);
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char> id) {
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char> id) {
     part_ = part::make_arg_name(id);
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_replacement_field(const Char* ptr) {
+  FMT_CONSTEXPR void on_replacement_field(int, const Char* ptr) {
     part_.arg_id_end = ptr;
     handler_(part_);
   }
 
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin,
+  FMT_CONSTEXPR const Char* on_format_specs(int, const Char* begin,
                                             const Char* end) {
     auto repl = typename part::replacement();
     dynamic_specs_handler<basic_format_parse_context<Char>> handler(
@@ -160,23 +191,24 @@ FMT_CONSTEXPR void compile_format_string(basic_string_view<Char> format_str,
       format_string_compiler<Char, PartHandler>(format_str, handler));
 }
 
-template <typename Range, typename Context, typename Id>
+template <typename OutputIt, typename Context, typename Id>
 void format_arg(
-    basic_format_parse_context<typename Range::value_type>& parse_ctx,
+    basic_format_parse_context<typename Context::char_type>& parse_ctx,
     Context& ctx, Id arg_id) {
-  ctx.advance_to(
-      visit_format_arg(arg_formatter<Range>(ctx, &parse_ctx), ctx.arg(arg_id)));
+  ctx.advance_to(visit_format_arg(
+      arg_formatter<OutputIt, typename Context::char_type>(ctx, &parse_ctx),
+      ctx.arg(arg_id)));
 }
 
 // vformat_to is defined in a subnamespace to prevent ADL.
 namespace cf {
-template <typename Context, typename Range, typename CompiledFormat>
-auto vformat_to(Range out, CompiledFormat& cf, basic_format_args<Context> args)
-    -> typename Context::iterator {
+template <typename Context, typename OutputIt, typename CompiledFormat>
+auto vformat_to(OutputIt out, CompiledFormat& cf,
+                basic_format_args<Context> args) -> typename Context::iterator {
   using char_type = typename Context::char_type;
   basic_format_parse_context<char_type> parse_ctx(
       to_string_view(cf.format_str_));
-  Context ctx(out.begin(), args);
+  Context ctx(out, args);
 
   const auto& parts = cf.parts();
   for (auto part_it = std::begin(parts); part_it != std::end(parts);
@@ -197,12 +229,12 @@ auto vformat_to(Range out, CompiledFormat& cf, basic_format_args<Context> args)
 
     case format_part_t::kind::arg_index:
       advance_to(parse_ctx, part.arg_id_end);
-      internal::format_arg<Range>(parse_ctx, ctx, value.arg_index);
+      detail::format_arg<OutputIt>(parse_ctx, ctx, value.arg_index);
       break;
 
     case format_part_t::kind::arg_name:
       advance_to(parse_ctx, part.arg_id_end);
-      internal::format_arg<Range>(parse_ctx, ctx, value.str);
+      detail::format_arg<OutputIt>(parse_ctx, ctx, value.str);
       break;
 
     case format_part_t::kind::replacement: {
@@ -226,7 +258,9 @@ auto vformat_to(Range out, CompiledFormat& cf, basic_format_args<Context> args)
 
       advance_to(parse_ctx, part.arg_id_end);
       ctx.advance_to(
-          visit_format_arg(arg_formatter<Range>(ctx, nullptr, &specs), arg));
+          visit_format_arg(arg_formatter<OutputIt, typename Context::char_type>(
+                               ctx, nullptr, &specs),
+                           arg));
       break;
     }
     }
@@ -240,7 +274,7 @@ struct basic_compiled_format {};
 template <typename S, typename = void>
 struct compiled_format_base : basic_compiled_format {
   using char_type = char_t<S>;
-  using parts_container = std::vector<internal::format_part<char_type>>;
+  using parts_container = std::vector<detail::format_part<char_type>>;
 
   parts_container compiled_parts;
 
@@ -305,7 +339,7 @@ struct compiled_format_base<S, enable_if_t<is_compile_string<S>::value>>
   const parts_container& parts() const {
     static FMT_CONSTEXPR_DECL const auto compiled_parts =
         compile_to_parts<char_type, num_format_parts>(
-            internal::to_string_view(S()));
+            detail::to_string_view(S()));
     return compiled_parts.data;
   }
 };
@@ -318,8 +352,8 @@ class compiled_format : private compiled_format_base<S> {
  private:
   basic_string_view<char_type> format_str_;
 
-  template <typename Context, typename Range, typename CompiledFormat>
-  friend auto cf::vformat_to(Range out, CompiledFormat& cf,
+  template <typename Context, typename OutputIt, typename CompiledFormat>
+  friend auto cf::vformat_to(OutputIt out, CompiledFormat& cf,
                              basic_format_args<Context> args) ->
       typename Context::iterator;
 
@@ -359,8 +393,7 @@ template <typename Char> struct text {
 
   template <typename OutputIt, typename... Args>
   OutputIt format(OutputIt out, const Args&...) const {
-    // TODO: reserve
-    return copy_str<Char>(data.begin(), data.end(), out);
+    return write<Char>(out, data);
   }
 };
 
@@ -373,33 +406,6 @@ constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
   return {{&s[pos], size}};
 }
 
-template <typename Char, typename OutputIt, typename T,
-          std::enable_if_t<std::is_integral_v<T>, int> = 0>
-OutputIt format_default(OutputIt out, T value) {
-  // TODO: reserve
-  format_int fi(value);
-  return std::copy(fi.data(), fi.data() + fi.size(), out);
-}
-
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, double value) {
-  writer w(out);
-  w.write(value);
-  return w.out();
-}
-
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, Char value) {
-  *out++ = value;
-  return out;
-}
-
-template <typename Char, typename OutputIt>
-OutputIt format_default(OutputIt out, const Char* value) {
-  auto length = std::char_traits<Char>::length(value);
-  return copy_str<Char>(value, value + length, out);
-}
-
 // A replacement field that refers to argument N.
 template <typename Char, typename T, int N> struct field {
   using char_type = Char;
@@ -408,13 +414,30 @@ template <typename Char, typename T, int N> struct field {
   OutputIt format(OutputIt out, const Args&... args) const {
     // This ensures that the argument type is convertile to `const T&`.
     const T& arg = get<N>(args...);
-    return format_default<Char>(out, arg);
+    return write<Char>(out, arg);
   }
 };
 
 template <typename Char, typename T, int N>
 struct is_compiled_format<field<Char, T, N>> : std::true_type {};
 
+// A replacement field that refers to argument N and has format specifiers.
+template <typename Char, typename T, int N> struct spec_field {
+  using char_type = Char;
+  mutable formatter<T, Char> fmt;
+
+  template <typename OutputIt, typename... Args>
+  OutputIt format(OutputIt out, const Args&... args) const {
+    // This ensures that the argument type is convertile to `const T&`.
+    const T& arg = get<N>(args...);
+    basic_format_context<OutputIt, Char> ctx(out, {});
+    return fmt.format(arg, ctx);
+  }
+};
+
+template <typename Char, typename T, int N>
+struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {};
+
 template <typename L, typename R> struct concat {
   L lhs;
   R rhs;
@@ -450,7 +473,8 @@ constexpr auto compile_format_string(S format_str);
 
 template <typename Args, size_t POS, int ID, typename T, typename S>
 constexpr auto parse_tail(T head, S format_str) {
-  if constexpr (POS != to_string_view(format_str).size()) {
+  if constexpr (POS !=
+                basic_string_view<typename S::char_type>(format_str).size()) {
     constexpr auto tail = compile_format_string<Args, POS, ID>(format_str);
     if constexpr (std::is_same<remove_cvref_t<decltype(tail)>,
                                unknown_format>())
@@ -462,6 +486,21 @@ constexpr auto parse_tail(T head, S format_str) {
   }
 }
 
+template <typename T, typename Char> struct parse_specs_result {
+  formatter<T, Char> fmt;
+  size_t end;
+};
+
+template <typename T, typename Char>
+constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
+                                                  size_t pos) {
+  str.remove_prefix(pos);
+  auto ctx = basic_format_parse_context<Char>(str);
+  auto f = formatter<T, Char>();
+  auto end = f.parse(ctx);
+  return {f, pos + (end - str.data()) + 1};
+}
+
 // Compiles a non-empty format string and returns the compiled representation
 // or unknown_format() on unrecognized input.
 template <typename Args, size_t POS, int ID, typename S>
@@ -475,12 +514,13 @@ constexpr auto compile_format_string(S format_str) {
       return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
     } else if constexpr (str[POS + 1] == '}') {
       using type = get_type<ID, Args>;
-      if constexpr (std::is_same<type, int>::value) {
-        return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
-                                                 format_str);
-      } else {
-        return unknown_format();
-      }
+      return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
+                                               format_str);
+    } else if constexpr (str[POS + 1] == ':') {
+      using type = get_type<ID, Args>;
+      constexpr auto result = parse_specs<type>(str, POS + 2);
+      return parse_tail<Args, result.end, ID + 1>(
+          spec_field<char_type, type, ID>{result.fmt}, format_str);
     } else {
       return unknown_format();
     }
@@ -494,100 +534,130 @@ constexpr auto compile_format_string(S format_str) {
                                      format_str);
   }
 }
-#endif  // __cpp_if_constexpr
-}  // namespace internal
 
-#if FMT_USE_CONSTEXPR
-#  ifdef __cpp_if_constexpr
 template <typename... Args, typename S,
-          FMT_ENABLE_IF(is_compile_string<S>::value)>
+          FMT_ENABLE_IF(is_compile_string<S>::value ||
+                        detail::is_compiled_string<S>::value)>
 constexpr auto compile(S format_str) {
   constexpr basic_string_view<typename S::char_type> str = format_str;
   if constexpr (str.size() == 0) {
-    return internal::make_text(str, 0, 0);
+    return detail::make_text(str, 0, 0);
   } else {
     constexpr auto result =
-        internal::compile_format_string<internal::type_list<Args...>, 0, 0>(
+        detail::compile_format_string<detail::type_list<Args...>, 0, 0>(
             format_str);
     if constexpr (std::is_same<remove_cvref_t<decltype(result)>,
-                               internal::unknown_format>()) {
-      return internal::compiled_format<S, Args...>(to_string_view(format_str));
+                               detail::unknown_format>()) {
+      return detail::compiled_format<S, Args...>(to_string_view(format_str));
     } else {
       return result;
     }
   }
 }
-
-template <typename CompiledFormat, typename... Args,
-          typename Char = typename CompiledFormat::char_type,
-          FMT_ENABLE_IF(internal::is_compiled_format<CompiledFormat>::value)>
-std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
-  basic_memory_buffer<Char> buffer;
-  cf.format(std::back_inserter(buffer), args...);
-  return to_string(buffer);
-}
-
-template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(internal::is_compiled_format<CompiledFormat>::value)>
-OutputIt format_to(OutputIt out, const CompiledFormat& cf,
-                   const Args&... args) {
-  return cf.format(out, args...);
-}
-#  else
+#else
 template <typename... Args, typename S,
           FMT_ENABLE_IF(is_compile_string<S>::value)>
-constexpr auto compile(S format_str) -> internal::compiled_format<S, Args...> {
-  return internal::compiled_format<S, Args...>(to_string_view(format_str));
+constexpr auto compile(S format_str) -> detail::compiled_format<S, Args...> {
+  return detail::compiled_format<S, Args...>(to_string_view(format_str));
 }
-#  endif  // __cpp_if_constexpr
-#endif    // FMT_USE_CONSTEXPR
+#endif  // __cpp_if_constexpr
 
 // Compiles the format string which must be a string literal.
 template <typename... Args, typename Char, size_t N>
 auto compile(const Char (&format_str)[N])
-    -> internal::compiled_format<const Char*, Args...> {
-  return internal::compiled_format<const Char*, Args...>(
+    -> detail::compiled_format<const Char*, Args...> {
+  return detail::compiled_format<const Char*, Args...>(
       basic_string_view<Char>(format_str, N - 1));
 }
+}  // namespace detail
+
+// DEPRECATED! use FMT_COMPILE instead.
+template <typename... Args>
+FMT_DEPRECATED auto compile(const Args&... args)
+    -> decltype(detail::compile(args...)) {
+  return detail::compile(args...);
+}
+
+#if FMT_USE_CONSTEXPR
+#  ifdef __cpp_if_constexpr
 
 template <typename CompiledFormat, typename... Args,
           typename Char = typename CompiledFormat::char_type,
-          FMT_ENABLE_IF(std::is_base_of<internal::basic_compiled_format,
-                                        CompiledFormat>::value)>
-std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
+                                          const Args&... args) {
   basic_memory_buffer<Char> buffer;
-  using range = buffer_range<Char>;
-  using context = buffer_context<Char>;
-  internal::cf::vformat_to<context>(range(buffer), cf,
-                                    make_format_args<context>(args...));
+  detail::buffer<Char>& base = buffer;
+  cf.format(std::back_inserter(base), args...);
   return to_string(buffer);
 }
 
 template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(std::is_base_of<internal::basic_compiled_format,
+          FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
+OutputIt format_to(OutputIt out, const CompiledFormat& cf,
+                   const Args&... args) {
+  return cf.format(out, args...);
+}
+#  endif  // __cpp_if_constexpr
+#endif    // FMT_USE_CONSTEXPR
+
+template <typename CompiledFormat, typename... Args,
+          typename Char = typename CompiledFormat::char_type,
+          FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
+                                        CompiledFormat>::value)>
+std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
+  basic_memory_buffer<Char> buffer;
+  using context = buffer_context<Char>;
+  detail::buffer<Char>& base = buffer;
+  detail::cf::vformat_to<context>(std::back_inserter(base), cf,
+                                  make_format_args<context>(args...));
+  return to_string(buffer);
+}
+
+template <typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
+                                                           Args&&... args) {
+  constexpr basic_string_view<typename S::char_type> str = S();
+  if (str.size() == 2 && str[0] == '{' && str[1] == '}')
+    return fmt::to_string(detail::first(args...));
+  constexpr auto compiled = detail::compile<Args...>(S());
+  return format(compiled, std::forward<Args>(args)...);
+}
+
+template <typename OutputIt, typename CompiledFormat, typename... Args,
+          FMT_ENABLE_IF(std::is_base_of<detail::basic_compiled_format,
                                         CompiledFormat>::value)>
 OutputIt format_to(OutputIt out, const CompiledFormat& cf,
                    const Args&... args) {
   using char_type = typename CompiledFormat::char_type;
-  using range = internal::output_range<OutputIt, char_type>;
   using context = format_context_t<OutputIt, char_type>;
-  return internal::cf::vformat_to<context>(range(out), cf,
-                                           make_format_args<context>(args...));
+  return detail::cf::vformat_to<context>(out, cf,
+                                         make_format_args<context>(args...));
 }
 
-template <typename OutputIt, typename CompiledFormat, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value)>
+template <typename OutputIt, typename S, typename... Args,
+          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+OutputIt format_to(OutputIt out, const S&, const Args&... args) {
+  constexpr auto compiled = detail::compile<Args...>(S());
+  return format_to(out, compiled, args...);
+}
+
+template <
+    typename OutputIt, typename CompiledFormat, typename... Args,
+    FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value&& std::is_base_of<
+                  detail::basic_compiled_format, CompiledFormat>::value)>
 format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
                                          const CompiledFormat& cf,
                                          const Args&... args) {
   auto it =
-      format_to(internal::truncating_iterator<OutputIt>(out, n), cf, args...);
+      format_to(detail::truncating_iterator<OutputIt>(out, n), cf, args...);
   return {it.base(), it.count()};
 }
 
 template <typename CompiledFormat, typename... Args>
-std::size_t formatted_size(const CompiledFormat& cf, const Args&... args) {
-  return format_to(internal::counting_iterator(), cf, args...).count();
+size_t formatted_size(const CompiledFormat& cf, const Args&... args) {
+  return format_to(detail::counting_iterator(), cf, args...).count();
 }
 
 FMT_END_NAMESPACE
diff --git a/include/fmt/core.h b/include/fmt/core.h
index 6df2875a..37799a3a 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -18,8 +18,45 @@
 #include <vector>
 
 // The fmt library version in the form major * 10000 + minor * 100 + patch.
-#define FMT_VERSION 60200
+#define FMT_VERSION 70003
 
+#ifdef __clang__
+#  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
+#else
+#  define FMT_CLANG_VERSION 0
+#endif
+
+#if defined(__GNUC__) && !defined(__clang__)
+#  define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
+#else
+#  define FMT_GCC_VERSION 0
+#endif
+
+#if defined(__INTEL_COMPILER)
+#  define FMT_ICC_VERSION __INTEL_COMPILER
+#else
+#  define FMT_ICC_VERSION 0
+#endif
+
+#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
+#  define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
+#else
+#  define FMT_HAS_GXX_CXX11 0
+#endif
+
+#ifdef __NVCC__
+#  define FMT_NVCC __NVCC__
+#else
+#  define FMT_NVCC 0
+#endif
+
+#ifdef _MSC_VER
+#  define FMT_MSC_VER _MSC_VER
+#  define FMT_SUPPRESS_MSC_WARNING(n) __pragma(warning(suppress : n))
+#else
+#  define FMT_MSC_VER 0
+#  define FMT_SUPPRESS_MSC_WARNING(n)
+#endif
 #ifdef __has_feature
 #  define FMT_HAS_FEATURE(x) __has_feature(x)
 #else
@@ -27,7 +64,7 @@
 #endif
 
 #if defined(__has_include) && !defined(__INTELLISENSE__) && \
-    !(defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1600)
+    !(FMT_ICC_VERSION && FMT_ICC_VERSION < 1600)
 #  define FMT_HAS_INCLUDE(x) __has_include(x)
 #else
 #  define FMT_HAS_INCLUDE(x) 0
@@ -45,43 +82,13 @@
 #define FMT_HAS_CPP17_ATTRIBUTE(attribute) \
   (__cplusplus >= 201703L && FMT_HAS_CPP_ATTRIBUTE(attribute))
 
-#ifdef __clang__
-#  define FMT_CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
-#else
-#  define FMT_CLANG_VERSION 0
-#endif
-
-#if defined(__GNUC__) && !defined(__clang__)
-#  define FMT_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
-#else
-#  define FMT_GCC_VERSION 0
-#endif
-
-#if __cplusplus >= 201103L || defined(__GXX_EXPERIMENTAL_CXX0X__)
-#  define FMT_HAS_GXX_CXX11 FMT_GCC_VERSION
-#else
-#  define FMT_HAS_GXX_CXX11 0
-#endif
-
-#ifdef __NVCC__
-#  define FMT_NVCC __NVCC__
-#else
-#  define FMT_NVCC 0
-#endif
-
-#ifdef _MSC_VER
-#  define FMT_MSC_VER _MSC_VER
-#else
-#  define FMT_MSC_VER 0
-#endif
-
 // Check if relaxed C++14 constexpr is supported.
 // GCC doesn't allow throw in constexpr until version 6 (bug 67371).
 #ifndef FMT_USE_CONSTEXPR
 #  define FMT_USE_CONSTEXPR                                           \
     (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
      (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L)) &&           \
-        !FMT_NVCC
+        !FMT_NVCC && !FMT_ICC_VERSION
 #endif
 #if FMT_USE_CONSTEXPR
 #  define FMT_CONSTEXPR constexpr
@@ -141,14 +148,6 @@
 #  define FMT_NORETURN
 #endif
 
-#ifndef FMT_MAYBE_UNUSED
-#  if FMT_HAS_CPP17_ATTRIBUTE(maybe_unused)
-#    define FMT_MAYBE_UNUSED [[maybe_unused]]
-#  else
-#    define FMT_MAYBE_UNUSED
-#  endif
-#endif
-
 #ifndef FMT_DEPRECATED
 #  if FMT_HAS_CPP14_ATTRIBUTE(deprecated) || FMT_MSC_VER >= 1900
 #    define FMT_DEPRECATED [[deprecated]]
@@ -164,12 +163,20 @@
 #endif
 
 // Workaround broken [[deprecated]] in the Intel, PGI and NVCC compilers.
-#if defined(__INTEL_COMPILER) || defined(__PGI) || FMT_NVCC
+#if FMT_ICC_VERSION || defined(__PGI) || FMT_NVCC
 #  define FMT_DEPRECATED_ALIAS
 #else
 #  define FMT_DEPRECATED_ALIAS FMT_DEPRECATED
 #endif
 
+#ifndef FMT_INLINE
+#  if FMT_GCC_VERSION || FMT_CLANG_VERSION
+#    define FMT_INLINE inline __attribute__((always_inline))
+#  else
+#    define FMT_INLINE inline
+#  endif
+#endif
+
 #ifndef FMT_BEGIN_NAMESPACE
 #  if FMT_HAS_FEATURE(cxx_inline_namespaces) || FMT_GCC_VERSION >= 404 || \
       FMT_MSC_VER >= 1900
@@ -181,39 +188,29 @@
 #    define FMT_INLINE_NAMESPACE namespace
 #    define FMT_END_NAMESPACE \
       }                       \
-      using namespace v6;     \
+      using namespace v7;     \
       }
 #  endif
 #  define FMT_BEGIN_NAMESPACE \
     namespace fmt {           \
-    FMT_INLINE_NAMESPACE v6 {
+    FMT_INLINE_NAMESPACE v7 {
 #endif
 
 #if !defined(FMT_HEADER_ONLY) && defined(_WIN32)
-#  if FMT_MSC_VER
-#    define FMT_NO_W4275 __pragma(warning(suppress : 4275))
-#  else
-#    define FMT_NO_W4275
-#  endif
-#  define FMT_CLASS_API FMT_NO_W4275
+#  define FMT_CLASS_API FMT_SUPPRESS_MSC_WARNING(4275)
 #  ifdef FMT_EXPORT
 #    define FMT_API __declspec(dllexport)
+#    define FMT_EXTERN_TEMPLATE_API FMT_API
+#    define FMT_EXPORTED
 #  elif defined(FMT_SHARED)
 #    define FMT_API __declspec(dllimport)
 #    define FMT_EXTERN_TEMPLATE_API FMT_API
 #  endif
-#endif
-#ifndef FMT_CLASS_API
+#else
 #  define FMT_CLASS_API
 #endif
 #ifndef FMT_API
-#  if FMT_GCC_VERSION || FMT_CLANG_VERSION
-#    define FMT_API __attribute__((visibility("default")))
-#    define FMT_EXTERN_TEMPLATE_API FMT_API
-#    define FMT_INSTANTIATION_DEF_API
-#  else
-#    define FMT_API
-#  endif
+#  define FMT_API
 #endif
 #ifndef FMT_EXTERN_TEMPLATE_API
 #  define FMT_EXTERN_TEMPLATE_API
@@ -270,14 +267,11 @@ struct monostate {};
 // to workaround a bug in MSVC 2019 (see #1140 and #1186).
 #define FMT_ENABLE_IF(...) enable_if_t<(__VA_ARGS__), int> = 0
 
-namespace internal {
+namespace detail {
 
 // A helper function to suppress bogus "conditional expression is constant"
 // warnings.
-template <typename T> FMT_CONSTEXPR T const_check(T value) { return value; }
-
-// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
-template <typename... Ts> struct void_t_impl { using type = void; };
+template <typename T> constexpr T const_check(T value) { return value; }
 
 FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
                                       const char* message);
@@ -290,7 +284,7 @@ FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
 #    define FMT_ASSERT(condition, message)                                    \
       ((condition) /* void() fails with -Winvalid-constexpr on clang 4.0.1 */ \
            ? (void)0                                                          \
-           : ::fmt::internal::assert_fail(__FILE__, __LINE__, (message)))
+           : ::fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
 #  endif
 #endif
 
@@ -305,7 +299,7 @@ template <typename T> struct std_string_view {};
 
 #ifdef FMT_USE_INT128
 // Do nothing.
-#elif defined(__SIZEOF_INT128__) && !FMT_NVCC
+#elif defined(__SIZEOF_INT128__) && !FMT_NVCC && !(FMT_CLANG_VERSION && FMT_MSC_VER)
 #  define FMT_USE_INT128 1
 using int128_t = __int128_t;
 using uint128_t = __uint128_t;
@@ -324,7 +318,7 @@ FMT_CONSTEXPR typename std::make_unsigned<Int>::type to_unsigned(Int value) {
   return static_cast<typename std::make_unsigned<Int>::type>(value);
 }
 
-constexpr unsigned char micro[] = "\u00B5";
+FMT_SUPPRESS_MSC_WARNING(4566) constexpr unsigned char micro[] = "\u00B5";
 
 template <typename Char> constexpr bool is_unicode() {
   return FMT_UNICODE || sizeof(Char) != 1 ||
@@ -336,10 +330,11 @@ using char8_type = char8_t;
 #else
 enum char8_type : unsigned char {};
 #endif
-}  // namespace internal
+}  // namespace detail
 
-template <typename... Ts>
-using void_t = typename internal::void_t_impl<Ts...>::type;
+#ifdef FMT_USE_INTERNAL
+namespace internal = detail;  // DEPRECATED
+#endif
 
 /**
   An implementation of ``std::basic_string_view`` for pre-C++17. It provides a
@@ -354,14 +349,13 @@ template <typename Char> class basic_string_view {
   size_t size_;
 
  public:
-  using char_type FMT_DEPRECATED_ALIAS = Char;
   using value_type = Char;
   using iterator = const Char*;
 
-  FMT_CONSTEXPR basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
+  constexpr basic_string_view() FMT_NOEXCEPT : data_(nullptr), size_(0) {}
 
   /** Constructs a string reference object from a C string and a size. */
-  FMT_CONSTEXPR basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
+  constexpr basic_string_view(const Char* s, size_t count) FMT_NOEXCEPT
       : data_(s),
         size_(count) {}
 
@@ -384,22 +378,21 @@ template <typename Char> class basic_string_view {
       : data_(s.data()),
         size_(s.size()) {}
 
-  template <
-      typename S,
-      FMT_ENABLE_IF(std::is_same<S, internal::std_string_view<Char>>::value)>
+  template <typename S, FMT_ENABLE_IF(std::is_same<
+                                      S, detail::std_string_view<Char>>::value)>
   FMT_CONSTEXPR basic_string_view(S s) FMT_NOEXCEPT : data_(s.data()),
                                                       size_(s.size()) {}
 
   /** Returns a pointer to the string data. */
-  FMT_CONSTEXPR const Char* data() const { return data_; }
+  constexpr const Char* data() const { return data_; }
 
   /** Returns the string size. */
-  FMT_CONSTEXPR size_t size() const { return size_; }
+  constexpr size_t size() const { return size_; }
 
-  FMT_CONSTEXPR iterator begin() const { return data_; }
-  FMT_CONSTEXPR iterator end() const { return data_ + size_; }
+  constexpr iterator begin() const { return data_; }
+  constexpr iterator end() const { return data_ + size_; }
 
-  FMT_CONSTEXPR const Char& operator[](size_t pos) const { return data_[pos]; }
+  constexpr const Char& operator[](size_t pos) const { return data_[pos]; }
 
   FMT_CONSTEXPR void remove_prefix(size_t n) {
     data_ += n;
@@ -438,16 +431,11 @@ template <typename Char> class basic_string_view {
 using string_view = basic_string_view<char>;
 using wstring_view = basic_string_view<wchar_t>;
 
-#ifndef __cpp_char8_t
-// char8_t is deprecated; use char instead.
-using char8_t FMT_DEPRECATED_ALIAS = internal::char8_type;
-#endif
-
 /** Specifies if ``T`` is a character type. Can be specialized by users. */
 template <typename T> struct is_char : std::false_type {};
 template <> struct is_char<char> : std::true_type {};
 template <> struct is_char<wchar_t> : std::true_type {};
-template <> struct is_char<internal::char8_type> : std::true_type {};
+template <> struct is_char<detail::char8_type> : std::true_type {};
 template <> struct is_char<char16_t> : std::true_type {};
 template <> struct is_char<char32_t> : std::true_type {};
 
@@ -484,14 +472,13 @@ inline basic_string_view<Char> to_string_view(basic_string_view<Char> s) {
 }
 
 template <typename Char,
-          FMT_ENABLE_IF(!std::is_empty<internal::std_string_view<Char>>::value)>
-inline basic_string_view<Char> to_string_view(
-    internal::std_string_view<Char> s) {
+          FMT_ENABLE_IF(!std::is_empty<detail::std_string_view<Char>>::value)>
+inline basic_string_view<Char> to_string_view(detail::std_string_view<Char> s) {
   return s;
 }
 
 // A base class for compile-time strings. It is defined in the fmt namespace to
-// make formatting functions visible via ADL, e.g. format(fmt("{}"), 42).
+// make formatting functions visible via ADL, e.g. format(FMT_STRING("{}"), 42).
 struct compile_string {};
 
 template <typename S>
@@ -502,9 +489,9 @@ constexpr basic_string_view<typename S::char_type> to_string_view(const S& s) {
   return s;
 }
 
-namespace internal {
+namespace detail {
 void to_string_view(...);
-using fmt::v6::to_string_view;
+using fmt::v7::to_string_view;
 
 // Specifies whether S is a string type convertible to fmt::basic_string_view.
 // It should be a constexpr function but MSVC 2017 fails to compile it in
@@ -520,16 +507,16 @@ template <typename S> struct char_t_impl<S, enable_if_t<is_string<S>::value>> {
 };
 
 struct error_handler {
-  FMT_CONSTEXPR error_handler() = default;
-  FMT_CONSTEXPR error_handler(const error_handler&) = default;
+  constexpr error_handler() = default;
+  constexpr error_handler(const error_handler&) = default;
 
   // This function is intentionally not constexpr to give a compile-time error.
   FMT_NORETURN FMT_API void on_error(const char* message);
 };
-}  // namespace internal
+}  // namespace detail
 
 /** String's character type. */
-template <typename S> using char_t = typename internal::char_t_impl<S>::type;
+template <typename S> using char_t = typename detail::char_t_impl<S>::type;
 
 /**
   \rst
@@ -547,7 +534,7 @@ template <typename S> using char_t = typename internal::char_t_impl<S>::type;
   +-----------------------+-------------------------------------+
   \endrst
  */
-template <typename Char, typename ErrorHandler = internal::error_handler>
+template <typename Char, typename ErrorHandler = detail::error_handler>
 class basic_format_parse_context : private ErrorHandler {
  private:
   basic_string_view<Char> format_str_;
@@ -557,26 +544,24 @@ class basic_format_parse_context : private ErrorHandler {
   using char_type = Char;
   using iterator = typename basic_string_view<Char>::iterator;
 
-  explicit FMT_CONSTEXPR basic_format_parse_context(
-      basic_string_view<Char> format_str, ErrorHandler eh = ErrorHandler())
+  explicit constexpr basic_format_parse_context(
+      basic_string_view<Char> format_str, ErrorHandler eh = {})
       : ErrorHandler(eh), format_str_(format_str), next_arg_id_(0) {}
 
   /**
     Returns an iterator to the beginning of the format string range being
     parsed.
    */
-  FMT_CONSTEXPR iterator begin() const FMT_NOEXCEPT {
-    return format_str_.begin();
-  }
+  constexpr iterator begin() const FMT_NOEXCEPT { return format_str_.begin(); }
 
   /**
     Returns an iterator past the end of the format string range being parsed.
    */
-  FMT_CONSTEXPR iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
+  constexpr iterator end() const FMT_NOEXCEPT { return format_str_.end(); }
 
   /** Advances the begin iterator to ``it``. */
   FMT_CONSTEXPR void advance_to(iterator it) {
-    format_str_.remove_prefix(internal::to_unsigned(it - begin()));
+    format_str_.remove_prefix(detail::to_unsigned(it - begin()));
   }
 
   /**
@@ -584,6 +569,8 @@ class basic_format_parse_context : private ErrorHandler {
     the next argument index and switches to the automatic indexing.
    */
   FMT_CONSTEXPR int next_arg_id() {
+    // Don't check if the argument id is valid to avoid overhead and because it
+    // will be checked during formatting anyway.
     if (next_arg_id_ >= 0) return next_arg_id_++;
     on_error("cannot switch from manual to automatic argument indexing");
     return 0;
@@ -606,20 +593,15 @@ class basic_format_parse_context : private ErrorHandler {
     ErrorHandler::on_error(message);
   }
 
-  FMT_CONSTEXPR ErrorHandler error_handler() const { return *this; }
+  constexpr ErrorHandler error_handler() const { return *this; }
 };
 
 using format_parse_context = basic_format_parse_context<char>;
 using wformat_parse_context = basic_format_parse_context<wchar_t>;
 
-template <typename Char, typename ErrorHandler = internal::error_handler>
-using basic_parse_context FMT_DEPRECATED_ALIAS =
-    basic_format_parse_context<Char, ErrorHandler>;
-using parse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<char>;
-using wparse_context FMT_DEPRECATED_ALIAS = basic_format_parse_context<wchar_t>;
-
 template <typename Context> class basic_format_arg;
 template <typename Context> class basic_format_args;
+template <typename Context> class dynamic_format_arg_store;
 
 // A formatter for objects of type T.
 template <typename T, typename Char = char, typename Enable = void>
@@ -628,43 +610,44 @@ struct formatter {
   formatter() = delete;
 };
 
-template <typename T, typename Char, typename Enable = void>
-struct FMT_DEPRECATED convert_to_int
-    : bool_constant<!std::is_arithmetic<T>::value &&
-                    std::is_convertible<T, int>::value> {};
-
 // Specifies if T has an enabled formatter specialization. A type can be
 // formattable even if it doesn't have a formatter e.g. via a conversion.
 template <typename T, typename Context>
 using has_formatter =
     std::is_constructible<typename Context::template formatter_type<T>>;
 
-namespace internal {
+namespace detail {
 
-/** A contiguous memory buffer with an optional growing ability. */
+/**
+  \rst
+  A contiguous memory buffer with an optional growing ability. It is an internal
+  class and shouldn't be used directly, only via `~fmt::basic_memory_buffer`.
+  \endrst
+ */
 template <typename T> class buffer {
  private:
   T* ptr_;
-  std::size_t size_;
-  std::size_t capacity_;
+  size_t size_;
+  size_t capacity_;
 
  protected:
   // Don't initialize ptr_ since it is not accessed to save a few cycles.
-  buffer(std::size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
+  FMT_SUPPRESS_MSC_WARNING(26495)
+  buffer(size_t sz) FMT_NOEXCEPT : size_(sz), capacity_(sz) {}
 
-  buffer(T* p = nullptr, std::size_t sz = 0, std::size_t cap = 0) FMT_NOEXCEPT
+  buffer(T* p = nullptr, size_t sz = 0, size_t cap = 0) FMT_NOEXCEPT
       : ptr_(p),
         size_(sz),
         capacity_(cap) {}
 
   /** Sets the buffer data and capacity. */
-  void set(T* buf_data, std::size_t buf_capacity) FMT_NOEXCEPT {
+  void set(T* buf_data, size_t buf_capacity) FMT_NOEXCEPT {
     ptr_ = buf_data;
     capacity_ = buf_capacity;
   }
 
   /** Increases the buffer capacity to hold at least *capacity* elements. */
-  virtual void grow(std::size_t capacity) = 0;
+  virtual void grow(size_t capacity) = 0;
 
  public:
   using value_type = T;
@@ -681,10 +664,10 @@ template <typename T> class buffer {
   const T* end() const FMT_NOEXCEPT { return ptr_ + size_; }
 
   /** Returns the size of this buffer. */
-  std::size_t size() const FMT_NOEXCEPT { return size_; }
+  size_t size() const FMT_NOEXCEPT { return size_; }
 
   /** Returns the capacity of this buffer. */
-  std::size_t capacity() const FMT_NOEXCEPT { return capacity_; }
+  size_t capacity() const FMT_NOEXCEPT { return capacity_; }
 
   /** Returns a pointer to the buffer data. */
   T* data() FMT_NOEXCEPT { return ptr_; }
@@ -695,7 +678,7 @@ template <typename T> class buffer {
   /**
     Resizes the buffer. If T is a POD type new elements may not be initialized.
    */
-  void resize(std::size_t new_size) {
+  void resize(size_t new_size) {
     reserve(new_size);
     size_ = new_size;
   }
@@ -704,7 +687,7 @@ template <typename T> class buffer {
   void clear() { size_ = 0; }
 
   /** Reserves space to store at least *capacity* elements. */
-  void reserve(std::size_t new_capacity) {
+  void reserve(size_t new_capacity) {
     if (new_capacity > capacity_) grow(new_capacity);
   }
 
@@ -729,7 +712,7 @@ class container_buffer : public buffer<typename Container::value_type> {
   Container& container_;
 
  protected:
-  void grow(std::size_t capacity) FMT_OVERRIDE {
+  void grow(size_t capacity) FMT_OVERRIDE {
     container_.resize(capacity);
     this->set(&container_[0], capacity);
   }
@@ -760,12 +743,78 @@ template <typename T, typename Context>
 using has_fallback_formatter =
     std::is_constructible<fallback_formatter<T, typename Context::char_type>>;
 
-template <typename Char> struct named_arg_base;
-template <typename T, typename Char> struct named_arg;
+struct view {};
+
+template <typename Char, typename T> struct named_arg : view {
+  const Char* name;
+  const T& value;
+  named_arg(const Char* n, const T& v) : name(n), value(v) {}
+};
+
+template <typename Char> struct named_arg_info {
+  const Char* name;
+  int id;
+};
+
+template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+struct arg_data {
+  // args_[0].named_args points to named_args_ to avoid bloating format_args.
+  T args_[1 + (NUM_ARGS != 0 ? NUM_ARGS : 1)];
+  named_arg_info<Char> named_args_[NUM_NAMED_ARGS];
+
+  template <typename... U>
+  arg_data(const U&... init) : args_{T(named_args_, NUM_NAMED_ARGS), init...} {}
+  arg_data(const arg_data& other) = delete;
+  const T* args() const { return args_ + 1; }
+  named_arg_info<Char>* named_args() { return named_args_; }
+};
+
+template <typename T, typename Char, size_t NUM_ARGS>
+struct arg_data<T, Char, NUM_ARGS, 0> {
+  T args_[NUM_ARGS != 0 ? NUM_ARGS : 1];
+
+  template <typename... U>
+  FMT_INLINE arg_data(const U&... init) : args_{init...} {}
+  FMT_INLINE const T* args() const { return args_; }
+  FMT_INLINE std::nullptr_t named_args() { return nullptr; }
+};
+
+template <typename Char>
+inline void init_named_args(named_arg_info<Char>*, int, int) {}
+
+template <typename Char, typename T, typename... Tail>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const T&, const Tail&... args) {
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
+
+template <typename Char, typename T, typename... Tail>
+void init_named_args(named_arg_info<Char>* named_args, int arg_count,
+                     int named_arg_count, const named_arg<Char, T>& arg,
+                     const Tail&... args) {
+  named_args[named_arg_count++] = {arg.name, arg_count};
+  init_named_args(named_args, arg_count + 1, named_arg_count, args...);
+}
+
+template <typename... Args>
+FMT_INLINE void init_named_args(std::nullptr_t, int, int, const Args&...) {}
+
+template <typename T> struct is_named_arg : std::false_type {};
+
+template <typename T, typename Char>
+struct is_named_arg<named_arg<Char, T>> : std::true_type {};
+
+template <bool B = false> constexpr size_t count() { return B ? 1 : 0; }
+template <bool B1, bool B2, bool... Tail> constexpr size_t count() {
+  return (B1 ? 1 : 0) + count<B2, Tail...>();
+}
+
+template <typename... Args> constexpr size_t count_named_args() {
+  return count<is_named_arg<Args>::value...>();
+}
 
 enum class type {
   none_type,
-  named_arg_type,
   // Integer types should go first,
   int_type,
   uint_type,
@@ -796,7 +845,6 @@ struct type_constant : std::integral_constant<type, type::custom_type> {};
   struct type_constant<Type, Char>        \
       : std::integral_constant<type, type::constant> {}
 
-FMT_TYPE_CONSTANT(const named_arg_base<Char>&, named_arg_type);
 FMT_TYPE_CONSTANT(int, int_type);
 FMT_TYPE_CONSTANT(unsigned, uint_type);
 FMT_TYPE_CONSTANT(long long, long_long_type);
@@ -812,23 +860,26 @@ FMT_TYPE_CONSTANT(const Char*, cstring_type);
 FMT_TYPE_CONSTANT(basic_string_view<Char>, string_type);
 FMT_TYPE_CONSTANT(const void*, pointer_type);
 
-FMT_CONSTEXPR bool is_integral_type(type t) {
-  FMT_ASSERT(t != type::named_arg_type, "invalid argument type");
+constexpr bool is_integral_type(type t) {
   return t > type::none_type && t <= type::last_integer_type;
 }
 
-FMT_CONSTEXPR bool is_arithmetic_type(type t) {
-  FMT_ASSERT(t != type::named_arg_type, "invalid argument type");
+constexpr bool is_arithmetic_type(type t) {
   return t > type::none_type && t <= type::last_numeric_type;
 }
 
 template <typename Char> struct string_value {
   const Char* data;
-  std::size_t size;
+  size_t size;
+};
+
+template <typename Char> struct named_arg_value {
+  const named_arg_info<Char>* data;
+  size_t size;
 };
 
 template <typename Context> struct custom_value {
-  using parse_context = basic_format_parse_context<typename Context::char_type>;
+  using parse_context = typename Context::parse_context_type;
   const void* value;
   void (*format)(const void* arg, parse_context& parse_ctx, Context& ctx);
 };
@@ -853,28 +904,30 @@ template <typename Context> class value {
     const void* pointer;
     string_value<char_type> string;
     custom_value<Context> custom;
-    const named_arg_base<char_type>* named_arg;
+    named_arg_value<char_type> named_args;
   };
 
-  FMT_CONSTEXPR value(int val = 0) : int_value(val) {}
-  FMT_CONSTEXPR value(unsigned val) : uint_value(val) {}
-  value(long long val) : long_long_value(val) {}
-  value(unsigned long long val) : ulong_long_value(val) {}
-  value(int128_t val) : int128_value(val) {}
-  value(uint128_t val) : uint128_value(val) {}
-  value(float val) : float_value(val) {}
-  value(double val) : double_value(val) {}
-  value(long double val) : long_double_value(val) {}
-  value(bool val) : bool_value(val) {}
-  value(char_type val) : char_value(val) {}
-  value(const char_type* val) { string.data = val; }
-  value(basic_string_view<char_type> val) {
+  constexpr FMT_INLINE value(int val = 0) : int_value(val) {}
+  constexpr FMT_INLINE value(unsigned val) : uint_value(val) {}
+  FMT_INLINE value(long long val) : long_long_value(val) {}
+  FMT_INLINE value(unsigned long long val) : ulong_long_value(val) {}
+  FMT_INLINE value(int128_t val) : int128_value(val) {}
+  FMT_INLINE value(uint128_t val) : uint128_value(val) {}
+  FMT_INLINE value(float val) : float_value(val) {}
+  FMT_INLINE value(double val) : double_value(val) {}
+  FMT_INLINE value(long double val) : long_double_value(val) {}
+  FMT_INLINE value(bool val) : bool_value(val) {}
+  FMT_INLINE value(char_type val) : char_value(val) {}
+  FMT_INLINE value(const char_type* val) { string.data = val; }
+  FMT_INLINE value(basic_string_view<char_type> val) {
     string.data = val.data();
     string.size = val.size();
   }
-  value(const void* val) : pointer(val) {}
+  FMT_INLINE value(const void* val) : pointer(val) {}
+  FMT_INLINE value(const named_arg_info<char_type>* args, size_t size)
+      : named_args{args, size} {}
 
-  template <typename T> value(const T& val) {
+  template <typename T> FMT_INLINE value(const T& val) {
     custom.value = &val;
     // Get the formatter type through the context to allow different contexts
     // have different extension points, e.g. `formatter<T>` for `format` and
@@ -885,14 +938,12 @@ template <typename Context> class value {
                          fallback_formatter<T, char_type>>>;
   }
 
-  value(const named_arg_base<char_type>& val) { named_arg = &val; }
-
  private:
   // Formats an argument of a custom type, such as a user-defined class.
   template <typename T, typename Formatter>
-  static void format_custom_arg(
-      const void* arg, basic_format_parse_context<char_type>& parse_ctx,
-      Context& ctx) {
+  static void format_custom_arg(const void* arg,
+                                typename Context::parse_context_type& parse_ctx,
+                                Context& ctx) {
     Formatter f;
     parse_ctx.advance_to(f.parse(parse_ctx));
     ctx.advance_to(f.format(*static_cast<const T*>(arg), ctx));
@@ -972,6 +1023,14 @@ template <typename Context> struct arg_mapper {
     static_assert(std::is_same<char_type, char>::value, "invalid string type");
     return reinterpret_cast<const char*>(val);
   }
+  FMT_CONSTEXPR const char* map(signed char* val) {
+    const auto* const_val = val;
+    return map(const_val);
+  }
+  FMT_CONSTEXPR const char* map(unsigned char* val) {
+    const auto* const_val = val;
+    return map(const_val);
+  }
 
   FMT_CONSTEXPR const void* map(void* val) { return val; }
   FMT_CONSTEXPR const void* map(const void* val) { return val; }
@@ -1003,11 +1062,9 @@ template <typename Context> struct arg_mapper {
   }
 
   template <typename T>
-  FMT_CONSTEXPR const named_arg_base<char_type>& map(
-      const named_arg<T, char_type>& val) {
-    auto arg = make_arg<Context>(val.value);
-    std::memcpy(val.data, &arg, sizeof(arg));
-    return val;
+  FMT_CONSTEXPR auto map(const named_arg<char_type, T>& val)
+      -> decltype(std::declval<arg_mapper>().map(val.value)) {
+    return map(val.value);
   }
 
   int map(...) {
@@ -1027,23 +1084,22 @@ using mapped_type_constant =
     type_constant<decltype(arg_mapper<Context>().map(std::declval<const T&>())),
                   typename Context::char_type>;
 
-enum { packed_arg_bits = 5 };
+enum { packed_arg_bits = 4 };
 // Maximum number of arguments with packed types.
-enum { max_packed_args = 63 / packed_arg_bits };
+enum { max_packed_args = 62 / packed_arg_bits };
 enum : unsigned long long { is_unpacked_bit = 1ULL << 63 };
-
-template <typename Context> class arg_map;
-}  // namespace internal
+enum : unsigned long long { has_named_args_bit = 1ULL << 62 };
+}  // namespace detail
 
 // A formatting argument. It is a trivially copyable/constructible type to
 // allow storage in basic_memory_buffer.
 template <typename Context> class basic_format_arg {
  private:
-  internal::value<Context> value_;
-  internal::type type_;
+  detail::value<Context> value_;
+  detail::type type_;
 
   template <typename ContextType, typename T>
-  friend FMT_CONSTEXPR basic_format_arg<ContextType> internal::make_arg(
+  friend FMT_CONSTEXPR basic_format_arg<ContextType> detail::make_arg(
       const T& value);
 
   template <typename Visitor, typename Ctx>
@@ -1052,34 +1108,40 @@ template <typename Context> class basic_format_arg {
       -> decltype(vis(0));
 
   friend class basic_format_args<Context>;
-  friend class internal::arg_map<Context>;
+  friend class dynamic_format_arg_store<Context>;
 
   using char_type = typename Context::char_type;
 
+  template <typename T, typename Char, size_t NUM_ARGS, size_t NUM_NAMED_ARGS>
+  friend struct detail::arg_data;
+
+  basic_format_arg(const detail::named_arg_info<char_type>* args, size_t size)
+      : value_(args, size) {}
+
  public:
   class handle {
    public:
-    explicit handle(internal::custom_value<Context> custom) : custom_(custom) {}
+    explicit handle(detail::custom_value<Context> custom) : custom_(custom) {}
 
-    void format(basic_format_parse_context<char_type>& parse_ctx,
+    void format(typename Context::parse_context_type& parse_ctx,
                 Context& ctx) const {
       custom_.format(custom_.value, parse_ctx, ctx);
     }
 
    private:
-    internal::custom_value<Context> custom_;
+    detail::custom_value<Context> custom_;
   };
 
-  FMT_CONSTEXPR basic_format_arg() : type_(internal::type::none_type) {}
+  constexpr basic_format_arg() : type_(detail::type::none_type) {}
 
-  FMT_CONSTEXPR explicit operator bool() const FMT_NOEXCEPT {
-    return type_ != internal::type::none_type;
+  constexpr explicit operator bool() const FMT_NOEXCEPT {
+    return type_ != detail::type::none_type;
   }
 
-  internal::type type() const { return type_; }
+  detail::type type() const { return type_; }
 
-  bool is_integral() const { return internal::is_integral_type(type_); }
-  bool is_arithmetic() const { return internal::is_arithmetic_type(type_); }
+  bool is_integral() const { return detail::is_integral_type(type_); }
+  bool is_arithmetic() const { return detail::is_arithmetic_type(type_); }
 };
 
 /**
@@ -1090,92 +1152,73 @@ template <typename Context> class basic_format_arg {
   \endrst
  */
 template <typename Visitor, typename Context>
-FMT_CONSTEXPR auto visit_format_arg(Visitor&& vis,
-                                    const basic_format_arg<Context>& arg)
-    -> decltype(vis(0)) {
+FMT_CONSTEXPR_DECL FMT_INLINE auto visit_format_arg(
+    Visitor&& vis, const basic_format_arg<Context>& arg) -> decltype(vis(0)) {
   using char_type = typename Context::char_type;
   switch (arg.type_) {
-  case internal::type::none_type:
+  case detail::type::none_type:
     break;
-  case internal::type::named_arg_type:
-    FMT_ASSERT(false, "invalid argument type");
-    break;
-  case internal::type::int_type:
+  case detail::type::int_type:
     return vis(arg.value_.int_value);
-  case internal::type::uint_type:
+  case detail::type::uint_type:
     return vis(arg.value_.uint_value);
-  case internal::type::long_long_type:
+  case detail::type::long_long_type:
     return vis(arg.value_.long_long_value);
-  case internal::type::ulong_long_type:
+  case detail::type::ulong_long_type:
     return vis(arg.value_.ulong_long_value);
 #if FMT_USE_INT128
-  case internal::type::int128_type:
+  case detail::type::int128_type:
     return vis(arg.value_.int128_value);
-  case internal::type::uint128_type:
+  case detail::type::uint128_type:
     return vis(arg.value_.uint128_value);
 #else
-  case internal::type::int128_type:
-  case internal::type::uint128_type:
+  case detail::type::int128_type:
+  case detail::type::uint128_type:
     break;
 #endif
-  case internal::type::bool_type:
+  case detail::type::bool_type:
     return vis(arg.value_.bool_value);
-  case internal::type::char_type:
+  case detail::type::char_type:
     return vis(arg.value_.char_value);
-  case internal::type::float_type:
+  case detail::type::float_type:
     return vis(arg.value_.float_value);
-  case internal::type::double_type:
+  case detail::type::double_type:
     return vis(arg.value_.double_value);
-  case internal::type::long_double_type:
+  case detail::type::long_double_type:
     return vis(arg.value_.long_double_value);
-  case internal::type::cstring_type:
+  case detail::type::cstring_type:
     return vis(arg.value_.string.data);
-  case internal::type::string_type:
+  case detail::type::string_type:
     return vis(basic_string_view<char_type>(arg.value_.string.data,
                                             arg.value_.string.size));
-  case internal::type::pointer_type:
+  case detail::type::pointer_type:
     return vis(arg.value_.pointer);
-  case internal::type::custom_type:
+  case detail::type::custom_type:
     return vis(typename basic_format_arg<Context>::handle(arg.value_.custom));
   }
   return vis(monostate());
 }
 
-namespace internal {
-// A map from argument names to their values for named arguments.
-template <typename Context> class arg_map {
- private:
-  using char_type = typename Context::char_type;
+// Checks whether T is a container with contiguous storage.
+template <typename T> struct is_contiguous : std::false_type {};
+template <typename Char>
+struct is_contiguous<std::basic_string<Char>> : std::true_type {};
+template <typename Char>
+struct is_contiguous<detail::buffer<Char>> : std::true_type {};
 
-  struct entry {
-    basic_string_view<char_type> name;
-    basic_format_arg<Context> arg;
-  };
+namespace detail {
 
-  entry* map_;
-  unsigned size_;
+template <typename OutputIt>
+struct is_back_insert_iterator : std::false_type {};
+template <typename Container>
+struct is_back_insert_iterator<std::back_insert_iterator<Container>>
+    : std::true_type {};
 
-  void push_back(value<Context> val) {
-    const auto& named = *val.named_arg;
-    map_[size_] = {named.name, named.template deserialize<Context>()};
-    ++size_;
-  }
-
- public:
-  arg_map(const arg_map&) = delete;
-  void operator=(const arg_map&) = delete;
-  arg_map() : map_(nullptr), size_(0) {}
-  void init(const basic_format_args<Context>& args);
-  ~arg_map() { delete[] map_; }
-
-  basic_format_arg<Context> find(basic_string_view<char_type> name) const {
-    // The list is unsorted, so just return the first matching name.
-    for (entry *it = map_, *end = map_ + size_; it != end; ++it) {
-      if (it->name == name) return it->arg;
-    }
-    return {};
-  }
-};
+template <typename OutputIt>
+struct is_contiguous_back_insert_iterator : std::false_type {};
+template <typename Container>
+struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
+    : is_contiguous<Container> {};
 
 // A type-erased reference to an std::locale to avoid heavy <locale> include.
 class locale_ref {
@@ -1207,23 +1250,30 @@ FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value) {
   return arg;
 }
 
-template <bool IS_PACKED, typename Context, typename T,
+// The type template parameter is there to avoid an ODR violation when using
+// a fallback formatter in one translation unit and an implicit conversion in
+// another (not recommended).
+template <bool IS_PACKED, typename Context, type, typename T,
           FMT_ENABLE_IF(IS_PACKED)>
 inline value<Context> make_arg(const T& val) {
   return arg_mapper<Context>().map(val);
 }
 
-template <bool IS_PACKED, typename Context, typename T,
+template <bool IS_PACKED, typename Context, type, typename T,
           FMT_ENABLE_IF(!IS_PACKED)>
 inline basic_format_arg<Context> make_arg(const T& value) {
   return make_arg<Context>(value);
 }
 
 template <typename T> struct is_reference_wrapper : std::false_type {};
-
 template <typename T>
 struct is_reference_wrapper<std::reference_wrapper<T>> : std::true_type {};
 
+template <typename T> const T& unwrap(const T& v) { return v; }
+template <typename T> const T& unwrap(const std::reference_wrapper<T>& v) {
+  return static_cast<const T&>(v);
+}
+
 class dynamic_arg_list {
   // Workaround for clang's -Wweak-vtables. Unlike for regular classes, for
   // templates it doesn't complain about inability to deduce single translation
@@ -1248,14 +1298,14 @@ class dynamic_arg_list {
 
  public:
   template <typename T, typename Arg> const T& push(const Arg& arg) {
-    auto node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
-    auto& value = node->value;
-    node->next = std::move(head_);
-    head_ = std::move(node);
+    auto new_node = std::unique_ptr<typed_node<T>>(new typed_node<T>(arg));
+    auto& value = new_node->value;
+    new_node->next = std::move(head_);
+    head_ = std::move(new_node);
     return value;
   }
 };
-}  // namespace internal
+}  // namespace detail
 
 // Formatting context.
 template <typename OutputIt, typename Char> class basic_format_context {
@@ -1266,12 +1316,12 @@ template <typename OutputIt, typename Char> class basic_format_context {
  private:
   OutputIt out_;
   basic_format_args<basic_format_context> args_;
-  internal::arg_map<basic_format_context> map_;
-  internal::locale_ref loc_;
+  detail::locale_ref loc_;
 
  public:
   using iterator = OutputIt;
   using format_arg = basic_format_arg<basic_format_context>;
+  using parse_context_type = basic_format_parse_context<Char>;
   template <typename T> using formatter_type = formatter<T, char_type>;
 
   basic_format_context(const basic_format_context&) = delete;
@@ -1282,34 +1332,38 @@ template <typename OutputIt, typename Char> class basic_format_context {
    */
   basic_format_context(OutputIt out,
                        basic_format_args<basic_format_context> ctx_args,
-                       internal::locale_ref loc = internal::locale_ref())
+                       detail::locale_ref loc = detail::locale_ref())
       : out_(out), args_(ctx_args), loc_(loc) {}
 
   format_arg arg(int id) const { return args_.get(id); }
+  format_arg arg(basic_string_view<char_type> name) { return args_.get(name); }
+  int arg_id(basic_string_view<char_type> name) { return args_.get_id(name); }
+  const basic_format_args<basic_format_context>& args() const { return args_; }
 
-  // Checks if manual indexing is used and returns the argument with the
-  // specified name.
-  format_arg arg(basic_string_view<char_type> name);
-
-  internal::error_handler error_handler() { return {}; }
+  detail::error_handler error_handler() { return {}; }
   void on_error(const char* message) { error_handler().on_error(message); }
 
   // Returns an iterator to the beginning of the output range.
   iterator out() { return out_; }
 
   // Advances the begin iterator to ``it``.
-  void advance_to(iterator it) { out_ = it; }
+  void advance_to(iterator it) {
+    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
+  }
 
-  internal::locale_ref locale() { return loc_; }
+  detail::locale_ref locale() { return loc_; }
 };
 
 template <typename Char>
 using buffer_context =
-    basic_format_context<std::back_insert_iterator<internal::buffer<Char>>,
-                         Char>;
+    basic_format_context<std::back_insert_iterator<detail::buffer<Char>>, Char>;
 using format_context = buffer_context<char>;
 using wformat_context = buffer_context<wchar_t>;
 
+// Workaround a bug in gcc: https://stackoverflow.com/q/62767544/471164.
+#define FMT_BUFFER_CONTEXT(Char) \
+  basic_format_context<std::back_insert_iterator<detail::buffer<Char>>, Char>
+
 /**
   \rst
   An array of references to arguments. It can be implicitly converted into
@@ -1326,27 +1380,35 @@ class format_arg_store
 {
  private:
   static const size_t num_args = sizeof...(Args);
-  static const bool is_packed = num_args < internal::max_packed_args;
+  static const size_t num_named_args = detail::count_named_args<Args...>();
+  static const bool is_packed = num_args <= detail::max_packed_args;
 
-  using value_type = conditional_t<is_packed, internal::value<Context>,
+  using value_type = conditional_t<is_packed, detail::value<Context>,
                                    basic_format_arg<Context>>;
 
-  // If the arguments are not packed, add one more element to mark the end.
-  value_type data_[num_args + (num_args == 0 ? 1 : 0)];
+  detail::arg_data<value_type, typename Context::char_type, num_args,
+                   num_named_args>
+      data_;
 
   friend class basic_format_args<Context>;
 
- public:
-  static constexpr unsigned long long types =
-      is_packed ? internal::encode_types<Context, Args...>()
-                : internal::is_unpacked_bit | num_args;
+  static constexpr unsigned long long desc =
+      (is_packed ? detail::encode_types<Context, Args...>()
+                 : detail::is_unpacked_bit | num_args) |
+      (num_named_args != 0
+           ? static_cast<unsigned long long>(detail::has_named_args_bit)
+           : 0);
 
+ public:
   format_arg_store(const Args&... args)
       :
 #if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
         basic_format_args<Context>(*this),
 #endif
-        data_{internal::make_arg<is_packed, Context>(args)...} {
+        data_{detail::make_arg<
+            is_packed, Context,
+            detail::mapped_type_constant<Args, Context>::value>(args)...} {
+    detail::init_named_args(data_.named_args(), 0, 0, args...);
   }
 };
 
@@ -1366,8 +1428,24 @@ inline format_arg_store<Context, Args...> make_format_args(
 
 /**
   \rst
-  A dynamic version of `fmt::format_arg_store<>`.
-  It's equipped with a storage to potentially temporary objects which lifetime
+  Returns a named argument to be used in a formatting function. It should only
+  be used in a call to a formatting function.
+
+  **Example**::
+
+    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
+  \endrst
+ */
+template <typename Char, typename T>
+inline detail::named_arg<Char, T> arg(const Char* name, const T& arg) {
+  static_assert(!detail::is_named_arg<T>(), "nested named arguments");
+  return {name, arg};
+}
+
+/**
+  \rst
+  A dynamic version of `fmt::format_arg_store`.
+  It's equipped with a storage to potentially temporary objects which lifetimes
   could be shorter than the format arguments object.
 
   It can be implicitly converted into `~fmt::basic_format_args` for passing
@@ -1385,49 +1463,73 @@ class dynamic_format_arg_store
   using char_type = typename Context::char_type;
 
   template <typename T> struct need_copy {
-    static constexpr internal::type mapped_type =
-        internal::mapped_type_constant<T, Context>::value;
+    static constexpr detail::type mapped_type =
+        detail::mapped_type_constant<T, Context>::value;
 
     enum {
-      value = !(internal::is_reference_wrapper<T>::value ||
+      value = !(detail::is_reference_wrapper<T>::value ||
                 std::is_same<T, basic_string_view<char_type>>::value ||
-                std::is_same<T, internal::std_string_view<char_type>>::value ||
-                (mapped_type != internal::type::cstring_type &&
-                 mapped_type != internal::type::string_type &&
-                 mapped_type != internal::type::custom_type &&
-                 mapped_type != internal::type::named_arg_type))
+                std::is_same<T, detail::std_string_view<char_type>>::value ||
+                (mapped_type != detail::type::cstring_type &&
+                 mapped_type != detail::type::string_type &&
+                 mapped_type != detail::type::custom_type))
     };
   };
 
   template <typename T>
-  using stored_type = conditional_t<internal::is_string<T>::value,
+  using stored_type = conditional_t<detail::is_string<T>::value,
                                     std::basic_string<char_type>, T>;
 
   // Storage of basic_format_arg must be contiguous.
   std::vector<basic_format_arg<Context>> data_;
+  std::vector<detail::named_arg_info<char_type>> named_info_;
 
   // Storage of arguments not fitting into basic_format_arg must grow
   // without relocation because items in data_ refer to it.
-  internal::dynamic_arg_list dynamic_args_;
+  detail::dynamic_arg_list dynamic_args_;
 
   friend class basic_format_args<Context>;
 
   unsigned long long get_types() const {
-    return internal::is_unpacked_bit | data_.size();
+    return detail::is_unpacked_bit | data_.size() |
+           (named_info_.empty()
+                ? 0ULL
+                : static_cast<unsigned long long>(detail::has_named_args_bit));
+  }
+
+  const basic_format_arg<Context>* data() const {
+    return named_info_.empty() ? data_.data() : data_.data() + 1;
   }
 
   template <typename T> void emplace_arg(const T& arg) {
-    data_.emplace_back(internal::make_arg<Context>(arg));
+    data_.emplace_back(detail::make_arg<Context>(arg));
+  }
+
+  template <typename T>
+  void emplace_arg(const detail::named_arg<char_type, T>& arg) {
+    if (named_info_.empty()) {
+      constexpr const detail::named_arg_info<char_type>* zero_ptr{nullptr};
+      data_.insert(data_.begin(), {zero_ptr, 0});
+    }
+    data_.emplace_back(detail::make_arg<Context>(detail::unwrap(arg.value)));
+    auto pop_one = [](std::vector<basic_format_arg<Context>>* data) {
+      data->pop_back();
+    };
+    std::unique_ptr<std::vector<basic_format_arg<Context>>, decltype(pop_one)>
+        guard{&data_, pop_one};
+    named_info_.push_back({arg.name, static_cast<int>(data_.size() - 2u)});
+    data_[0].value_.named_args = {named_info_.data(), named_info_.size()};
+    guard.release();
   }
 
  public:
   /**
     \rst
-    Adds an argument into the dynamic store for later passing to a formating
+    Adds an argument into the dynamic store for later passing to a formatting
     function.
 
-    Note that custom types and string types (but not string views!) are copied
-    into the store with dynamic memory (in addition to resizing vector).
+    Note that custom types and string types (but not string views) are copied
+    into the store dynamically allocating memory if necessary.
 
     **Example**::
 
@@ -1439,25 +1541,78 @@ class dynamic_format_arg_store
     \endrst
   */
   template <typename T> void push_back(const T& arg) {
-    static_assert(
-        !std::is_base_of<internal::named_arg_base<char_type>, T>::value,
-        "named arguments are not supported yet");
-    if (internal::const_check(need_copy<T>::value))
+    if (detail::const_check(need_copy<T>::value))
       emplace_arg(dynamic_args_.push<stored_type<T>>(arg));
     else
-      emplace_arg(arg);
+      emplace_arg(detail::unwrap(arg));
   }
 
   /**
+    \rst
     Adds a reference to the argument into the dynamic store for later passing to
-    a formating function.
+    a formatting function. Supports named arguments wrapped in
+    ``std::reference_wrapper`` via ``std::ref()``/``std::cref()``.
+
+    **Example**::
+
+      fmt::dynamic_format_arg_store<fmt::format_context> store;
+      char str[] = "1234567890";
+      store.push_back(std::cref(str));
+      int a1_val{42};
+      auto a1 = fmt::arg("a1_", a1_val);
+      store.push_back(std::cref(a1));
+
+      // Changing str affects the output but only for string and custom types.
+      str[0] = 'X';
+
+      std::string result = fmt::vformat("{} and {a1_}");
+      assert(result == "X234567890 and 42");
+    \endrst
   */
   template <typename T> void push_back(std::reference_wrapper<T> arg) {
     static_assert(
-        need_copy<T>::value,
+        detail::is_named_arg<typename std::remove_cv<T>::type>::value ||
+            need_copy<T>::value,
         "objects of built-in types and string views are always copied");
     emplace_arg(arg.get());
   }
+
+  /**
+    Adds named argument into the dynamic store for later passing to a formatting
+    function. ``std::reference_wrapper`` is supported to avoid copying of the
+    argument.
+  */
+  template <typename T>
+  void push_back(const detail::named_arg<char_type, T>& arg) {
+    const char_type* arg_name =
+        dynamic_args_.push<std::basic_string<char_type>>(arg.name).c_str();
+    if (detail::const_check(need_copy<T>::value)) {
+      emplace_arg(
+          fmt::arg(arg_name, dynamic_args_.push<stored_type<T>>(arg.value)));
+    } else {
+      emplace_arg(fmt::arg(arg_name, arg.value));
+    }
+  }
+
+  /** Erase all elements from the store */
+  void clear() {
+    data_.clear();
+    named_info_.clear();
+    dynamic_args_ = detail::dynamic_arg_list();
+  }
+
+  /**
+    \rst
+    Reserves space to store at least *new_cap* arguments including
+    *new_cap_named* named arguments.
+    \endrst
+  */
+  void reserve(size_t new_cap, size_t new_cap_named) {
+    FMT_ASSERT(new_cap >= new_cap_named,
+               "Set of arguments includes set of named arguments");
+    data_.reserve(new_cap);
+    named_info_.reserve(new_cap_named);
+  }
 };
 
 /**
@@ -1476,49 +1631,40 @@ template <typename Context> class basic_format_args {
   using format_arg = basic_format_arg<Context>;
 
  private:
-  // To reduce compiled code size per formatting function call, types of first
-  // max_packed_args arguments are passed in the types_ field.
-  unsigned long long types_;
+  // A descriptor that contains information about formatting arguments.
+  // If the number of arguments is less or equal to max_packed_args then
+  // argument types are passed in the descriptor. This reduces binary code size
+  // per formatting function call.
+  unsigned long long desc_;
   union {
-    // If the number of arguments is less than max_packed_args, the argument
-    // values are stored in values_, otherwise they are stored in args_.
-    // This is done to reduce compiled code size as storing larger objects
+    // If is_packed() returns true then argument values are stored in values_;
+    // otherwise they are stored in args_. This is done to improve cache
+    // locality and reduce compiled code size since storing larger objects
     // may require more code (at least on x86-64) even if the same amount of
     // data is actually copied to stack. It saves ~10% on the bloat test.
-    const internal::value<Context>* values_;
+    const detail::value<Context>* values_;
     const format_arg* args_;
   };
 
-  bool is_packed() const { return (types_ & internal::is_unpacked_bit) == 0; }
-
-  internal::type type(int index) const {
-    int shift = index * internal::packed_arg_bits;
-    unsigned int mask = (1 << internal::packed_arg_bits) - 1;
-    return static_cast<internal::type>((types_ >> shift) & mask);
+  bool is_packed() const { return (desc_ & detail::is_unpacked_bit) == 0; }
+  bool has_named_args() const {
+    return (desc_ & detail::has_named_args_bit) != 0;
   }
 
-  friend class internal::arg_map<Context>;
-
-  void set_data(const internal::value<Context>* values) { values_ = values; }
-  void set_data(const format_arg* args) { args_ = args; }
-
-  format_arg do_get(int index) const {
-    format_arg arg;
-    if (!is_packed()) {
-      auto num_args = max_size();
-      if (index < num_args) arg = args_[index];
-      return arg;
-    }
-    if (index > internal::max_packed_args) return arg;
-    arg.type_ = type(index);
-    if (arg.type_ == internal::type::none_type) return arg;
-    internal::value<Context>& val = arg.value_;
-    val = values_[index];
-    return arg;
+  detail::type type(int index) const {
+    int shift = index * detail::packed_arg_bits;
+    unsigned int mask = (1 << detail::packed_arg_bits) - 1;
+    return static_cast<detail::type>((desc_ >> shift) & mask);
   }
 
+  basic_format_args(unsigned long long desc,
+                    const detail::value<Context>* values)
+      : desc_(desc), values_(values) {}
+  basic_format_args(unsigned long long desc, const format_arg* args)
+      : desc_(desc), args_(args) {}
+
  public:
-  basic_format_args() : types_(0) {}
+  basic_format_args() : desc_(0) {}
 
   /**
    \rst
@@ -1526,10 +1672,8 @@ template <typename Context> class basic_format_args {
    \endrst
    */
   template <typename... Args>
-  basic_format_args(const format_arg_store<Context, Args...>& store)
-      : types_(store.types) {
-    set_data(store.data_);
-  }
+  FMT_INLINE basic_format_args(const format_arg_store<Context, Args...>& store)
+      : basic_format_args(store.desc, store.data_.args()) {}
 
   /**
    \rst
@@ -1537,10 +1681,8 @@ template <typename Context> class basic_format_args {
    `~fmt::dynamic_format_arg_store`.
    \endrst
    */
-  basic_format_args(const dynamic_format_arg_store<Context>& store)
-      : types_(store.get_types()) {
-    set_data(store.data_.data());
-  }
+  FMT_INLINE basic_format_args(const dynamic_format_arg_store<Context>& store)
+      : basic_format_args(store.get_types(), store.data()) {}
 
   /**
    \rst
@@ -1548,22 +1690,42 @@ template <typename Context> class basic_format_args {
    \endrst
    */
   basic_format_args(const format_arg* args, int count)
-      : types_(internal::is_unpacked_bit | internal::to_unsigned(count)) {
-    set_data(args);
-  }
+      : basic_format_args(detail::is_unpacked_bit | detail::to_unsigned(count),
+                          args) {}
 
-  /** Returns the argument at specified index. */
-  format_arg get(int index) const {
-    format_arg arg = do_get(index);
-    if (arg.type_ == internal::type::named_arg_type)
-      arg = arg.value_.named_arg->template deserialize<Context>();
+  /** Returns the argument with the specified id. */
+  format_arg get(int id) const {
+    format_arg arg;
+    if (!is_packed()) {
+      if (id < max_size()) arg = args_[id];
+      return arg;
+    }
+    if (id >= detail::max_packed_args) return arg;
+    arg.type_ = type(id);
+    if (arg.type_ == detail::type::none_type) return arg;
+    arg.value_ = values_[id];
     return arg;
   }
 
+  template <typename Char> format_arg get(basic_string_view<Char> name) const {
+    int id = get_id(name);
+    return id >= 0 ? get(id) : format_arg();
+  }
+
+  template <typename Char> int get_id(basic_string_view<Char> name) const {
+    if (!has_named_args()) return -1;
+    const auto& named_args =
+        (is_packed() ? values_[-1] : args_[-1].value_).named_args;
+    for (size_t i = 0; i < named_args.size; ++i) {
+      if (named_args.data[i].name == name) return named_args.data[i].id;
+    }
+    return -1;
+  }
+
   int max_size() const {
-    unsigned long long max_packed = internal::max_packed_args;
+    unsigned long long max_packed = detail::max_packed_args;
     return static_cast<int>(is_packed() ? max_packed
-                                        : types_ & ~internal::is_unpacked_bit);
+                                        : desc_ & ~detail::is_unpacked_bit);
   }
 };
 
@@ -1571,93 +1733,48 @@ template <typename Context> class basic_format_args {
 // It is a separate type rather than an alias to make symbols readable.
 struct format_args : basic_format_args<format_context> {
   template <typename... Args>
-  format_args(Args&&... args)
-      : basic_format_args<format_context>(static_cast<Args&&>(args)...) {}
+  FMT_INLINE format_args(const Args&... args) : basic_format_args(args...) {}
 };
 struct wformat_args : basic_format_args<wformat_context> {
-  template <typename... Args>
-  wformat_args(Args&&... args)
-      : basic_format_args<wformat_context>(static_cast<Args&&>(args)...) {}
+  using basic_format_args::basic_format_args;
 };
 
-template <typename Container> struct is_contiguous : std::false_type {};
-
-template <typename Char>
-struct is_contiguous<std::basic_string<Char>> : std::true_type {};
-
-template <typename Char>
-struct is_contiguous<internal::buffer<Char>> : std::true_type {};
-
-namespace internal {
-
-template <typename OutputIt>
-struct is_contiguous_back_insert_iterator : std::false_type {};
-template <typename Container>
-struct is_contiguous_back_insert_iterator<std::back_insert_iterator<Container>>
-    : is_contiguous<Container> {};
-
-template <typename Char> struct named_arg_base {
-  basic_string_view<Char> name;
-
-  // Serialized value<context>.
-  mutable char data[sizeof(basic_format_arg<buffer_context<Char>>)];
-
-  named_arg_base(basic_string_view<Char> nm) : name(nm) {}
-
-  template <typename Context> basic_format_arg<Context> deserialize() const {
-    basic_format_arg<Context> arg;
-    std::memcpy(&arg, data, sizeof(basic_format_arg<Context>));
-    return arg;
-  }
-};
-
-struct view {};
-
-template <typename T, typename Char>
-struct named_arg : view, named_arg_base<Char> {
-  const T& value;
-
-  named_arg(basic_string_view<Char> name, const T& val)
-      : named_arg_base<Char>(name), value(val) {}
-};
+namespace detail {
 
+// Reports a compile-time error if S is not a valid format string.
 template <typename..., typename S, FMT_ENABLE_IF(!is_compile_string<S>::value)>
-inline void check_format_string(const S&) {
-#if defined(FMT_ENFORCE_COMPILE_STRING)
+FMT_INLINE void check_format_string(const S&) {
+#ifdef FMT_ENFORCE_COMPILE_STRING
   static_assert(is_compile_string<S>::value,
-                "FMT_ENFORCE_COMPILE_STRING requires all format strings to "
-                "utilize FMT_STRING() or fmt().");
+                "FMT_ENFORCE_COMPILE_STRING requires all format strings to use "
+                "FMT_STRING.");
 #endif
 }
 template <typename..., typename S, FMT_ENABLE_IF(is_compile_string<S>::value)>
 void check_format_string(S);
 
-template <bool...> struct bool_pack;
-template <bool... Args>
-using all_true =
-    std::is_same<bool_pack<Args..., true>, bool_pack<true, Args...>>;
-
 template <typename... Args, typename S, typename Char = char_t<S>>
 inline format_arg_store<buffer_context<Char>, remove_reference_t<Args>...>
 make_args_checked(const S& format_str,
                   const remove_reference_t<Args>&... args) {
-  static_assert(
-      all_true<(!std::is_base_of<view, remove_reference_t<Args>>::value ||
-                !std::is_reference<Args>::value)...>::value,
-      "passing views as lvalues is disallowed");
+  static_assert(count<(std::is_base_of<view, remove_reference_t<Args>>::value &&
+                       std::is_reference<Args>::value)...>() == 0,
+                "passing views as lvalues is disallowed");
   check_format_string<Args...>(format_str);
   return {args...};
 }
 
-template <typename Char>
+template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
 std::basic_string<Char> vformat(
     basic_string_view<Char> format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args);
 
+FMT_API std::string vformat(string_view format_str, format_args args);
+
 template <typename Char>
-typename buffer_context<Char>::iterator vformat_to(
+typename FMT_BUFFER_CONTEXT(Char)::iterator vformat_to(
     buffer<Char>& buf, basic_string_view<Char> format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args);
+    basic_format_args<FMT_BUFFER_CONTEXT(type_identity_t<Char>)> args);
 
 template <typename Char, typename Args,
           FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
@@ -1667,58 +1784,38 @@ FMT_API void vprint_mojibake(std::FILE*, string_view, format_args);
 #ifndef _WIN32
 inline void vprint_mojibake(std::FILE*, string_view, format_args) {}
 #endif
-}  // namespace internal
-
-/**
-  \rst
-  Returns a named argument to be used in a formatting function. It should only
-  be used in a call to a formatting function.
-
-  **Example**::
-
-    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
-  \endrst
- */
-template <typename S, typename T, typename Char = char_t<S>>
-inline internal::named_arg<T, Char> arg(const S& name, const T& arg) {
-  static_assert(internal::is_string<S>::value, "");
-  return {name, arg};
-}
-
-// Disable nested named arguments, e.g. ``arg("a", arg("b", 42))``.
-template <typename S, typename T, typename Char>
-void arg(S, internal::named_arg<T, Char>) = delete;
+}  // namespace detail
 
 /** Formats a string and writes the output to ``out``. */
 // GCC 8 and earlier cannot handle std::back_insert_iterator<Container> with
 // vformat_to<ArgFormatter>(...) overload, so SFINAE on iterator type instead.
-template <typename OutputIt, typename S, typename Char = char_t<S>,
-          FMT_ENABLE_IF(
-              internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
+template <
+    typename OutputIt, typename S, typename Char = char_t<S>,
+    FMT_ENABLE_IF(detail::is_contiguous_back_insert_iterator<OutputIt>::value)>
 OutputIt vformat_to(
     OutputIt out, const S& format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  using container = remove_reference_t<decltype(internal::get_container(out))>;
-  internal::container_buffer<container> buf((internal::get_container(out)));
-  internal::vformat_to(buf, to_string_view(format_str), args);
+  auto& c = detail::get_container(out);
+  detail::container_buffer<remove_reference_t<decltype(c)>> buf(c);
+  detail::vformat_to(buf, to_string_view(format_str), args);
   return out;
 }
 
 template <typename Container, typename S, typename... Args,
           FMT_ENABLE_IF(
-              is_contiguous<Container>::value&& internal::is_string<S>::value)>
+              is_contiguous<Container>::value&& detail::is_string<S>::value)>
 inline std::back_insert_iterator<Container> format_to(
     std::back_insert_iterator<Container> out, const S& format_str,
     Args&&... args) {
   return vformat_to(out, to_string_view(format_str),
-                    internal::make_args_checked<Args...>(format_str, args...));
+                    detail::make_args_checked<Args...>(format_str, args...));
 }
 
 template <typename S, typename Char = char_t<S>>
-inline std::basic_string<Char> vformat(
+FMT_INLINE std::basic_string<Char> vformat(
     const S& format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  return internal::vformat(to_string_view(format_str), args);
+  return detail::vformat(to_string_view(format_str), args);
 }
 
 /**
@@ -1734,10 +1831,9 @@ inline std::basic_string<Char> vformat(
 // Pass char_t as a default template parameter instead of using
 // std::basic_string<char_t<S>> to reduce the symbol size.
 template <typename S, typename... Args, typename Char = char_t<S>>
-inline std::basic_string<Char> format(const S& format_str, Args&&... args) {
-  return internal::vformat(
-      to_string_view(format_str),
-      internal::make_args_checked<Args...>(format_str, args...));
+FMT_INLINE std::basic_string<Char> format(const S& format_str, Args&&... args) {
+  const auto& vargs = detail::make_args_checked<Args...>(format_str, args...);
+  return detail::vformat(to_string_view(format_str), vargs);
 }
 
 FMT_API void vprint(string_view, format_args);
@@ -1756,12 +1852,10 @@ FMT_API void vprint(std::FILE*, string_view, format_args);
  */
 template <typename S, typename... Args, typename Char = char_t<S>>
 inline void print(std::FILE* f, const S& format_str, Args&&... args) {
-  return internal::is_unicode<Char>()
-             ? vprint(f, to_string_view(format_str),
-                      internal::make_args_checked<Args...>(format_str, args...))
-             : internal::vprint_mojibake(
-                   f, to_string_view(format_str),
-                   internal::make_args_checked<Args...>(format_str, args...));
+  const auto& vargs = detail::make_args_checked<Args...>(format_str, args...);
+  return detail::is_unicode<Char>()
+             ? vprint(f, to_string_view(format_str), vargs)
+             : detail::vprint_mojibake(f, to_string_view(format_str), vargs);
 }
 
 /**
@@ -1777,12 +1871,11 @@ inline void print(std::FILE* f, const S& format_str, Args&&... args) {
  */
 template <typename S, typename... Args, typename Char = char_t<S>>
 inline void print(const S& format_str, Args&&... args) {
-  return internal::is_unicode<Char>()
-             ? vprint(to_string_view(format_str),
-                      internal::make_args_checked<Args...>(format_str, args...))
-             : internal::vprint_mojibake(
-                   stdout, to_string_view(format_str),
-                   internal::make_args_checked<Args...>(format_str, args...));
+  const auto& vargs = detail::make_args_checked<Args...>(format_str, args...);
+  return detail::is_unicode<Char>()
+             ? vprint(to_string_view(format_str), vargs)
+             : detail::vprint_mojibake(stdout, to_string_view(format_str),
+                                       vargs);
 }
 FMT_END_NAMESPACE
 
diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index f632714d..d8c9c8a5 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -15,6 +15,7 @@
 #include <cstdarg>
 #include <cstring>  // for std::memmove
 #include <cwchar>
+#include <exception>
 
 #include "format.h"
 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
@@ -22,8 +23,16 @@
 #endif
 
 #ifdef _WIN32
+#  if !defined(NOMINMAX) && !defined(WIN32_LEAN_AND_MEAN)
+#    define NOMINMAX
+#    define WIN32_LEAN_AND_MEAN
+#    include <windows.h>
+#    undef WIN32_LEAN_AND_MEAN
+#    undef NOMINMAX
+#  else
+#    include <windows.h>
+#  endif
 #  include <io.h>
-#  include <windows.h>
 #endif
 
 #ifdef _MSC_VER
@@ -33,15 +42,19 @@
 
 // Dummy implementations of strerror_r and strerror_s called if corresponding
 // system functions are not available.
-inline fmt::internal::null<> strerror_r(int, char*, ...) { return {}; }
-inline fmt::internal::null<> strerror_s(char*, std::size_t, ...) { return {}; }
+inline fmt::detail::null<> strerror_r(int, char*, ...) { return {}; }
+inline fmt::detail::null<> strerror_s(char*, size_t, ...) { return {}; }
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
 FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
-  print(stderr, "{}:{}: assertion failed: {}", file, line, message);
-  std::abort();
+  // Use unchecked std::fprintf to avoid triggering another assertion when
+  // writing to stderr fails
+  std::fprintf(stderr, "%s:%d: assertion failed: %s", file, line, message);
+  // Chosen instead of std::abort to satisfy Clang in CUDA mode during device
+  // code pass.
+  std::terminate();
 }
 
 #ifndef _MSC_VER
@@ -67,14 +80,14 @@ inline int fmt_snprintf(char* buffer, size_t size, const char* format, ...) {
 //   other  - failure
 // Buffer should be at least of size 1.
 FMT_FUNC int safe_strerror(int error_code, char*& buffer,
-                           std::size_t buffer_size) FMT_NOEXCEPT {
+                           size_t buffer_size) FMT_NOEXCEPT {
   FMT_ASSERT(buffer != nullptr && buffer_size != 0, "invalid buffer");
 
   class dispatcher {
    private:
     int error_code_;
     char*& buffer_;
-    std::size_t buffer_size_;
+    size_t buffer_size_;
 
     // A noop assignment operator to avoid bogus warnings.
     void operator=(const dispatcher&) {}
@@ -97,7 +110,7 @@ FMT_FUNC int safe_strerror(int error_code, char*& buffer,
 
     // Handle the case when strerror_r is not available.
     FMT_MAYBE_UNUSED
-    int handle(internal::null<>) {
+    int handle(detail::null<>) {
       return fallback(strerror_s(buffer_, buffer_size_, error_code_));
     }
 
@@ -111,7 +124,7 @@ FMT_FUNC int safe_strerror(int error_code, char*& buffer,
 
 #if !FMT_MSC_VER
     // Fallback to strerror if strerror_r and strerror_s are not available.
-    int fallback(internal::null<>) {
+    int fallback(detail::null<>) {
       errno = 0;
       buffer_ = strerror(error_code_);
       return errno;
@@ -119,7 +132,7 @@ FMT_FUNC int safe_strerror(int error_code, char*& buffer,
 #endif
 
    public:
-    dispatcher(int err_code, char*& buf, std::size_t buf_size)
+    dispatcher(int err_code, char*& buf, size_t buf_size)
         : error_code_(err_code), buffer_(buf), buffer_size_(buf_size) {}
 
     int run() { return handle(strerror_r(error_code_, buffer_, buffer_size_)); }
@@ -127,7 +140,7 @@ FMT_FUNC int safe_strerror(int error_code, char*& buffer,
   return dispatcher(error_code, buffer, buffer_size).run();
 }
 
-FMT_FUNC void format_error_code(internal::buffer<char>& out, int error_code,
+FMT_FUNC void format_error_code(detail::buffer<char>& out, int error_code,
                                 string_view message) FMT_NOEXCEPT {
   // Report error code making sure that the output fits into
   // inline_buffer_size to avoid dynamic memory allocation and potential
@@ -136,20 +149,17 @@ FMT_FUNC void format_error_code(internal::buffer<char>& out, int error_code,
   static const char SEP[] = ": ";
   static const char ERROR_STR[] = "error ";
   // Subtract 2 to account for terminating null characters in SEP and ERROR_STR.
-  std::size_t error_code_size = sizeof(SEP) + sizeof(ERROR_STR) - 2;
+  size_t error_code_size = sizeof(SEP) + sizeof(ERROR_STR) - 2;
   auto abs_value = static_cast<uint32_or_64_or_128_t<int>>(error_code);
-  if (internal::is_negative(error_code)) {
+  if (detail::is_negative(error_code)) {
     abs_value = 0 - abs_value;
     ++error_code_size;
   }
-  error_code_size += internal::to_unsigned(internal::count_digits(abs_value));
-  internal::writer w(out);
-  if (message.size() <= inline_buffer_size - error_code_size) {
-    w.write(message);
-    w.write(SEP);
-  }
-  w.write(ERROR_STR);
-  w.write(error_code);
+  error_code_size += detail::to_unsigned(detail::count_digits(abs_value));
+  auto it = std::back_inserter(out);
+  if (message.size() <= inline_buffer_size - error_code_size)
+    format_to(it, "{}{}", message, SEP);
+  format_to(it, "{}{}", ERROR_STR, error_code);
   assert(out.size() <= inline_buffer_size);
 }
 
@@ -168,10 +178,10 @@ FMT_FUNC void fwrite_fully(const void* ptr, size_t size, size_t count,
   size_t written = std::fwrite(ptr, size, count, stream);
   if (written < count) FMT_THROW(system_error(errno, "cannot write to file"));
 }
-}  // namespace internal
+}  // namespace detail
 
 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
-namespace internal {
+namespace detail {
 
 template <typename Locale>
 locale_ref::locale_ref(const Locale& loc) : locale_(&loc) {
@@ -194,18 +204,16 @@ template <typename Char> FMT_FUNC Char decimal_point_impl(locale_ref loc) {
   return std::use_facet<std::numpunct<Char>>(loc.get<std::locale>())
       .decimal_point();
 }
-}  // namespace internal
+}  // namespace detail
 #else
 template <typename Char>
-FMT_FUNC std::string internal::grouping_impl(locale_ref) {
+FMT_FUNC std::string detail::grouping_impl(locale_ref) {
   return "\03";
 }
-template <typename Char>
-FMT_FUNC Char internal::thousands_sep_impl(locale_ref) {
+template <typename Char> FMT_FUNC Char detail::thousands_sep_impl(locale_ref) {
   return FMT_STATIC_THOUSANDS_SEPARATOR;
 }
-template <typename Char>
-FMT_FUNC Char internal::decimal_point_impl(locale_ref) {
+template <typename Char> FMT_FUNC Char detail::decimal_point_impl(locale_ref) {
   return '.';
 }
 #endif
@@ -222,9 +230,9 @@ FMT_FUNC void system_error::init(int err_code, string_view format_str,
   base = std::runtime_error(to_string(buffer));
 }
 
-namespace internal {
+namespace detail {
 
-template <> FMT_FUNC int count_digits<4>(internal::fallback_uintptr n) {
+template <> FMT_FUNC int count_digits<4>(detail::fallback_uintptr n) {
   // fallback_uintptr is always stored in little endian.
   int i = static_cast<int>(sizeof(void*)) - 1;
   while (i > 0 && n.value[i] == 0) --i;
@@ -233,12 +241,27 @@ template <> FMT_FUNC int count_digits<4>(internal::fallback_uintptr n) {
 }
 
 template <typename T>
-const char basic_data<T>::digits[] =
-    "0001020304050607080910111213141516171819"
-    "2021222324252627282930313233343536373839"
-    "4041424344454647484950515253545556575859"
-    "6061626364656667686970717273747576777879"
-    "8081828384858687888990919293949596979899";
+const typename basic_data<T>::digit_pair basic_data<T>::digits[] = {
+    {'0', '0'},  {'0', '1'},  {'0', '2'},  {'0', '3'},  {'0', '4'},
+    {'0', '5'},  {'0', '6'},  {'0', '7'},  {'0', '8'},  {'0', '9'},
+    {'1', '0'},  {'1', '1'},  {'1', '2'},  {'1', '3'},  {'1', '4'},
+    {'1', '5'},  {'1', '6'},  {'1', '7'},  {'1', '8'},  {'1', '9'},
+    {'2', '0'},  {'2', '1'},  {'2', '2'},  {'2', '3'},  {'2', '4'},
+    {'2', '5'},  {'2', '6'},  {'2', '7'},  {'2', '8'},  {'2', '9'},
+    {'3', '0'},  {'3', '1'},  {'3', '2'},  {'3', '3'},  {'3', '4'},
+    {'3', '5'},  {'3', '6'},  {'3', '7'},  {'3', '8'},  {'3', '9'},
+    {'4', '0'},  {'4', '1'},  {'4', '2'},  {'4', '3'},  {'4', '4'},
+    {'4', '5'},  {'4', '6'},  {'4', '7'},  {'4', '8'},  {'4', '9'},
+    {'5', '0'},  {'5', '1'},  {'5', '2'},  {'5', '3'},  {'5', '4'},
+    {'5', '5'},  {'5', '6'},  {'5', '7'},  {'5', '8'},  {'5', '9'},
+    {'6', '0'},  {'6', '1'},  {'6', '2'},  {'6', '3'},  {'6', '4'},
+    {'6', '5'},  {'6', '6'},  {'6', '7'},  {'6', '8'},  {'6', '9'},
+    {'7', '0'},  {'7', '1'},  {'7', '2'},  {'7', '3'},  {'7', '4'},
+    {'7', '5'},  {'7', '6'},  {'7', '7'},  {'7', '8'},  {'7', '9'},
+    {'8', '0'},  {'8', '1'},  {'8', '2'},  {'8', '3'},  {'8', '4'},
+    {'8', '5'},  {'8', '6'},  {'8', '7'},  {'8', '8'},  {'8', '9'},
+    {'9', '0'},  {'9', '1'},  {'9', '2'},  {'9', '3'},  {'9', '4'},
+    {'9', '5'},  {'9', '6'},  {'9', '7'},  {'9', '8'},  {'9', '9'}};
 
 template <typename T>
 const char basic_data<T>::hex_digits[] = "0123456789abcdef";
@@ -317,6 +340,10 @@ const char basic_data<T>::background_color[] = "\x1b[48;2;";
 template <typename T> const char basic_data<T>::reset_color[] = "\x1b[0m";
 template <typename T> const wchar_t basic_data<T>::wreset_color[] = L"\x1b[0m";
 template <typename T> const char basic_data<T>::signs[] = {0, '-', '+', ' '};
+template <typename T>
+const char basic_data<T>::left_padding_shifts[] = {31, 31, 0, 1, 0};
+template <typename T>
+const char basic_data<T>::right_padding_shifts[] = {0, 31, 0, 1, 0};
 
 template <typename T> struct bits {
   static FMT_CONSTEXPR_DECL const int value =
@@ -576,9 +603,10 @@ class bigint {
   void operator=(const bigint&) = delete;
 
   void assign(const bigint& other) {
-    bigits_.resize(other.bigits_.size());
+    auto size = other.bigits_.size();
+    bigits_.resize(size);
     auto data = other.bigits_.data();
-    std::copy(data, data + other.bigits_.size(), bigits_.data());
+    std::copy(data, data + size, make_checked(bigits_.data(), size));
     exp_ = other.exp_;
   }
 
@@ -594,7 +622,7 @@ class bigint {
 
   int num_bigits() const { return static_cast<int>(bigits_.size()) + exp_; }
 
-  bigint& operator<<=(int shift) {
+  FMT_NOINLINE bigint& operator<<=(int shift) {
     assert(shift >= 0);
     exp_ += shift / bigit_bits;
     shift %= bigit_bits;
@@ -1125,7 +1153,7 @@ int snprintf_float(T value, int precision, float_specs specs,
     precision = (precision >= 0 ? precision : 6) - 1;
 
   // Build the format string.
-  enum { max_format_size = 7 };  // Ths longest format is "%#.*Le".
+  enum { max_format_size = 7 };  // The longest format is "%#.*Le".
   char format[max_format_size];
   char* format_ptr = format;
   *format_ptr++ = '%';
@@ -1145,13 +1173,13 @@ int snprintf_float(T value, int precision, float_specs specs,
   for (;;) {
     auto begin = buf.data() + offset;
     auto capacity = buf.capacity() - offset;
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+#ifdef FMT_FUZZ
     if (precision > 100000)
       throw std::runtime_error(
           "fuzz mode - avoid large allocation inside snprintf");
 #endif
     // Suppress the warning about a nonliteral format string.
-    // Cannot use auto becase of a bug in MinGW (#1532).
+    // Cannot use auto because of a bug in MinGW (#1532).
     int (*snprintf_ptr)(char*, size_t, const char*, ...) = FMT_SNPRINTF;
     int result = precision >= 0
                      ? snprintf_ptr(begin, capacity, format, precision, value)
@@ -1268,14 +1296,14 @@ FMT_FUNC const char* utf8_decode(const char* buf, uint32_t* c, int* e) {
 
   return next;
 }
-}  // namespace internal
+}  // namespace detail
 
-template <> struct formatter<internal::bigint> {
+template <> struct formatter<detail::bigint> {
   format_parse_context::iterator parse(format_parse_context& ctx) {
     return ctx.begin();
   }
 
-  format_context::iterator format(const internal::bigint& n,
+  format_context::iterator format(const detail::bigint& n,
                                   format_context& ctx) {
     auto out = ctx.out();
     bool first = true;
@@ -1289,12 +1317,12 @@ template <> struct formatter<internal::bigint> {
       out = format_to(out, "{:08x}", value);
     }
     if (n.exp_ > 0)
-      out = format_to(out, "p{}", n.exp_ * internal::bigint::bigit_bits);
+      out = format_to(out, "p{}", n.exp_ * detail::bigint::bigit_bits);
     return out;
   }
 };
 
-FMT_FUNC internal::utf8_to_utf16::utf8_to_utf16(string_view s) {
+FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
   auto transcode = [this](const char* p) {
     auto cp = uint32_t();
     auto error = 0;
@@ -1325,7 +1353,7 @@ FMT_FUNC internal::utf8_to_utf16::utf8_to_utf16(string_view s) {
   buffer_.push_back(0);
 }
 
-FMT_FUNC void format_system_error(internal::buffer<char>& out, int error_code,
+FMT_FUNC void format_system_error(detail::buffer<char>& out, int error_code,
                                   string_view message) FMT_NOEXCEPT {
   FMT_TRY {
     memory_buffer buf;
@@ -1333,12 +1361,9 @@ FMT_FUNC void format_system_error(internal::buffer<char>& out, int error_code,
     for (;;) {
       char* system_message = &buf[0];
       int result =
-          internal::safe_strerror(error_code, system_message, buf.size());
+          detail::safe_strerror(error_code, system_message, buf.size());
       if (result == 0) {
-        internal::writer w(out);
-        w.write(message);
-        w.write(": ");
-        w.write(system_message);
+        format_to(std::back_inserter(out), "{}: {}", message, system_message);
         return;
       }
       if (result != ERANGE)
@@ -1350,7 +1375,7 @@ FMT_FUNC void format_system_error(internal::buffer<char>& out, int error_code,
   format_error_code(out, error_code, message);
 }
 
-FMT_FUNC void internal::error_handler::on_error(const char* message) {
+FMT_FUNC void detail::error_handler::on_error(const char* message) {
   FMT_THROW(format_error(message));
 }
 
@@ -1359,14 +1384,39 @@ FMT_FUNC void report_system_error(int error_code,
   report_error(format_system_error, error_code, message);
 }
 
+struct stringifier {
+  template <typename T> FMT_INLINE std::string operator()(T value) const {
+    return to_string(value);
+  }
+  std::string operator()(basic_format_arg<format_context>::handle h) const {
+    memory_buffer buf;
+    detail::buffer<char>& base = buf;
+    format_parse_context parse_ctx({});
+    format_context format_ctx(std::back_inserter(base), {}, {});
+    h.format(parse_ctx, format_ctx);
+    return to_string(buf);
+  }
+};
+
+FMT_FUNC std::string detail::vformat(string_view format_str, format_args args) {
+  if (format_str.size() == 2 && equal2(format_str.data(), "{}")) {
+    auto arg = args.get(0);
+    if (!arg) error_handler().on_error("argument not found");
+    return visit_format_arg(stringifier(), arg);
+  }
+  memory_buffer buffer;
+  detail::vformat_to(buffer, format_str, args);
+  return to_string(buffer);
+}
+
 FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args) {
   memory_buffer buffer;
-  internal::vformat_to(buffer, format_str,
-                       basic_format_args<buffer_context<char>>(args));
+  detail::vformat_to(buffer, format_str,
+                     basic_format_args<buffer_context<char>>(args));
 #ifdef _WIN32
   auto fd = _fileno(f);
   if (_isatty(fd)) {
-    internal::utf8_to_utf16 u16(string_view(buffer.data(), buffer.size()));
+    detail::utf8_to_utf16 u16(string_view(buffer.data(), buffer.size()));
     auto written = DWORD();
     if (!WriteConsoleW(reinterpret_cast<HANDLE>(_get_osfhandle(fd)),
                        u16.c_str(), static_cast<DWORD>(u16.size()), &written,
@@ -1376,16 +1426,16 @@ FMT_FUNC void vprint(std::FILE* f, string_view format_str, format_args args) {
     return;
   }
 #endif
-  internal::fwrite_fully(buffer.data(), 1, buffer.size(), f);
+  detail::fwrite_fully(buffer.data(), 1, buffer.size(), f);
 }
 
 #ifdef _WIN32
 // Print assuming legacy (non-Unicode) encoding.
-FMT_FUNC void internal::vprint_mojibake(std::FILE* f, string_view format_str,
-                                        format_args args) {
+FMT_FUNC void detail::vprint_mojibake(std::FILE* f, string_view format_str,
+                                      format_args args) {
   memory_buffer buffer;
-  internal::vformat_to(buffer, format_str,
-                       basic_format_args<buffer_context<char>>(args));
+  detail::vformat_to(buffer, format_str,
+                     basic_format_args<buffer_context<char>>(args));
   fwrite_fully(buffer.data(), 1, buffer.size(), f);
 }
 #endif
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 4e96539f..17509b7b 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -43,10 +43,6 @@
 
 #include "core.h"
 
-#ifdef FMT_DEPRECATED_INCLUDE_OS
-#  include "os.h"
-#endif
-
 #ifdef __INTEL_COMPILER
 #  define FMT_ICC_VERSION __INTEL_COMPILER
 #elif defined(__ICL)
@@ -76,7 +72,8 @@
 #if __cplusplus == 201103L || __cplusplus == 201402L
 #  if defined(__clang__)
 #    define FMT_FALLTHROUGH [[clang::fallthrough]]
-#  elif FMT_GCC_VERSION >= 700 && !defined(__PGI)
+#  elif FMT_GCC_VERSION >= 700 && !defined(__PGI) && \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= 520)
 #    define FMT_FALLTHROUGH [[gnu::fallthrough]]
 #  else
 #    define FMT_FALLTHROUGH
@@ -88,20 +85,28 @@
 #  define FMT_FALLTHROUGH
 #endif
 
+#ifndef FMT_MAYBE_UNUSED
+#  if FMT_HAS_CPP17_ATTRIBUTE(maybe_unused)
+#    define FMT_MAYBE_UNUSED [[maybe_unused]]
+#  else
+#    define FMT_MAYBE_UNUSED
+#  endif
+#endif
+
 #ifndef FMT_THROW
 #  if FMT_EXCEPTIONS
 #    if FMT_MSC_VER || FMT_NVCC
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 template <typename Exception> inline void do_throw(const Exception& x) {
   // Silence unreachable code warnings in MSVC and NVCC because these
   // are nearly impossible to fix in a generic code.
   volatile bool b = true;
   if (b) throw x;
 }
-}  // namespace internal
+}  // namespace detail
 FMT_END_NAMESPACE
-#      define FMT_THROW(x) internal::do_throw(x)
+#      define FMT_THROW(x) detail::do_throw(x)
 #    else
 #      define FMT_THROW(x) throw x
 #    endif
@@ -123,11 +128,10 @@ FMT_END_NAMESPACE
 #endif
 
 #ifndef FMT_USE_USER_DEFINED_LITERALS
-// For Intel and NVIDIA compilers both they and the system gcc/msc support UDLs.
-#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 407 ||      \
-       FMT_MSC_VER >= 1900) &&                                              \
-      (!(FMT_ICC_VERSION || FMT_CUDA_VERSION) || FMT_ICC_VERSION >= 1500 || \
-       FMT_CUDA_VERSION >= 700)
+// EDG based compilers (Intel, NVIDIA, Elbrus, etc), GCC and MSVC support UDLs.
+#  if (FMT_HAS_FEATURE(cxx_user_literals) || FMT_GCC_VERSION >= 407 || \
+       FMT_MSC_VER >= 1900) &&                                         \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= /* UDL feature */ 480)
 #    define FMT_USE_USER_DEFINED_LITERALS 1
 #  else
 #    define FMT_USE_USER_DEFINED_LITERALS 0
@@ -135,12 +139,11 @@ FMT_END_NAMESPACE
 #endif
 
 #ifndef FMT_USE_UDL_TEMPLATE
-// EDG front end based compilers (icc, nvcc) and GCC < 6.4 do not propertly
+// EDG frontend based compilers (icc, nvcc, etc) and GCC < 6.4 do not properly
 // support UDL templates and GCC >= 9 warns about them.
-#  if FMT_USE_USER_DEFINED_LITERALS && FMT_ICC_VERSION == 0 && \
-      FMT_CUDA_VERSION == 0 &&                                 \
-      ((FMT_GCC_VERSION >= 604 && FMT_GCC_VERSION <= 900 &&    \
-        __cplusplus >= 201402L) ||                             \
+#  if FMT_USE_USER_DEFINED_LITERALS &&                         \
+      (!defined(__EDG_VERSION__) || __EDG_VERSION__ >= 501) && \
+      ((FMT_GCC_VERSION >= 604 && __cplusplus >= 201402L) ||   \
        FMT_CLANG_VERSION >= 304)
 #    define FMT_USE_UDL_TEMPLATE 1
 #  else
@@ -176,7 +179,7 @@ FMT_END_NAMESPACE
 #  include <intrin.h>  // _BitScanReverse, _BitScanReverse64
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 // Avoid Clang with Microsoft CodeGen's -Wunknown-pragmas warning.
 #  ifndef __clang__
 #    pragma intrinsic(_BitScanReverse)
@@ -189,10 +192,10 @@ inline uint32_t clz(uint32_t x) {
   // Static analysis complains about using uninitialized data
   // "r", but the only way that can happen is if "x" is 0,
   // which the callers guarantee to not happen.
-#  pragma warning(suppress : 6102)
+  FMT_SUPPRESS_MSC_WARNING(6102)
   return 31 - r;
 }
-#  define FMT_BUILTIN_CLZ(n) internal::clz(n)
+#  define FMT_BUILTIN_CLZ(n) detail::clz(n)
 
 #  if defined(_WIN64) && !defined(__clang__)
 #    pragma intrinsic(_BitScanReverse64)
@@ -214,26 +217,21 @@ inline uint32_t clzll(uint64_t x) {
   // Static analysis complains about using uninitialized data
   // "r", but the only way that can happen is if "x" is 0,
   // which the callers guarantee to not happen.
-#  pragma warning(suppress : 6102)
+  FMT_SUPPRESS_MSC_WARNING(6102)
   return 63 - r;
 }
-#  define FMT_BUILTIN_CLZLL(n) internal::clzll(n)
-}  // namespace internal
+#  define FMT_BUILTIN_CLZLL(n) detail::clzll(n)
+}  // namespace detail
 FMT_END_NAMESPACE
 #endif
 
 // Enable the deprecated numeric alignment.
-#ifndef FMT_NUMERIC_ALIGN
-#  define FMT_NUMERIC_ALIGN 1
-#endif
-
-// Enable the deprecated percent specifier.
-#ifndef FMT_DEPRECATED_PERCENT
-#  define FMT_DEPRECATED_PERCENT 0
+#ifndef FMT_DEPRECATED_NUMERIC_ALIGN
+#  define FMT_DEPRECATED_NUMERIC_ALIGN 0
 #endif
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
 // An equivalent of `*reinterpret_cast<Dest*>(&source)` that doesn't have
 // undefined behavior (e.g. due to type aliasing).
@@ -285,14 +283,31 @@ template <typename T> constexpr T max_value() {
 template <typename T> constexpr int num_bits() {
   return std::numeric_limits<T>::digits;
 }
+// std::numeric_limits<T>::digits may return 0 for 128-bit ints.
+template <> constexpr int num_bits<int128_t>() { return 128; }
+template <> constexpr int num_bits<uint128_t>() { return 128; }
 template <> constexpr int num_bits<fallback_uintptr>() {
   return static_cast<int>(sizeof(void*) *
                           std::numeric_limits<unsigned char>::digits);
 }
 
+FMT_INLINE void assume(bool condition) {
+  (void)condition;
+#if FMT_HAS_BUILTIN(__builtin_assume)
+  __builtin_assume(condition);
+#endif
+}
+
+// A workaround for gcc 4.8 to make void_t work in a SFINAE context.
+template <typename... Ts> struct void_t_impl { using type = void; };
+
+template <typename... Ts>
+using void_t = typename detail::void_t_impl<Ts...>::type;
+
 // An approximation of iterator_t for pre-C++20 systems.
 template <typename T>
 using iterator_t = decltype(std::begin(std::declval<T&>()));
+template <typename T> using sentinel_t = decltype(std::end(std::declval<T&>()));
 
 // Detect the iterator category of *any* given type in a SFINAE-friendly way.
 // Unfortunately, older implementations of std::iterator_traits are not safe
@@ -339,25 +354,39 @@ inline typename Container::value_type* get_data(Container& c) {
 #if defined(_SECURE_SCL) && _SECURE_SCL
 // Make a checked iterator to avoid MSVC warnings.
 template <typename T> using checked_ptr = stdext::checked_array_iterator<T*>;
-template <typename T> checked_ptr<T> make_checked(T* p, std::size_t size) {
+template <typename T> checked_ptr<T> make_checked(T* p, size_t size) {
   return {p, size};
 }
 #else
 template <typename T> using checked_ptr = T*;
-template <typename T> inline T* make_checked(T* p, std::size_t) { return p; }
+template <typename T> inline T* make_checked(T* p, size_t) { return p; }
 #endif
 
 template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
-inline checked_ptr<typename Container::value_type> reserve(
-    std::back_insert_iterator<Container>& it, std::size_t n) {
+#if FMT_CLANG_VERSION
+__attribute__((no_sanitize("undefined")))
+#endif
+inline checked_ptr<typename Container::value_type>
+reserve(std::back_insert_iterator<Container> it, size_t n) {
   Container& c = get_container(it);
-  std::size_t size = c.size();
+  size_t size = c.size();
   c.resize(size + n);
   return make_checked(get_data(c) + size, n);
 }
 
+template <typename Iterator> inline Iterator& reserve(Iterator& it, size_t) {
+  return it;
+}
+
+template <typename Container, FMT_ENABLE_IF(is_contiguous<Container>::value)>
+inline std::back_insert_iterator<Container> base_iterator(
+    std::back_insert_iterator<Container>& it,
+    checked_ptr<typename Container::value_type>) {
+  return it;
+}
+
 template <typename Iterator>
-inline Iterator& reserve(Iterator& it, std::size_t) {
+inline Iterator base_iterator(Iterator, Iterator it) {
   return it;
 }
 
@@ -365,7 +394,7 @@ inline Iterator& reserve(Iterator& it, std::size_t) {
 // discards them.
 class counting_iterator {
  private:
-  std::size_t count_;
+  size_t count_;
 
  public:
   using iterator_category = std::output_iterator_tag;
@@ -380,7 +409,7 @@ class counting_iterator {
 
   counting_iterator() : count_(0) {}
 
-  std::size_t count() const { return count_; }
+  size_t count() const { return count_; }
 
   counting_iterator& operator++() {
     ++count_;
@@ -399,10 +428,10 @@ class counting_iterator {
 template <typename OutputIt> class truncating_iterator_base {
  protected:
   OutputIt out_;
-  std::size_t limit_;
-  std::size_t count_;
+  size_t limit_;
+  size_t count_;
 
-  truncating_iterator_base(OutputIt out, std::size_t limit)
+  truncating_iterator_base(OutputIt out, size_t limit)
       : out_(out), limit_(limit), count_(0) {}
 
  public:
@@ -415,7 +444,7 @@ template <typename OutputIt> class truncating_iterator_base {
       truncating_iterator_base;  // Mark iterator as checked.
 
   OutputIt base() const { return out_; }
-  std::size_t count() const { return count_; }
+  size_t count() const { return count_; }
 };
 
 // An output iterator that truncates the output and counts the number of objects
@@ -433,7 +462,7 @@ class truncating_iterator<OutputIt, std::false_type>
  public:
   using value_type = typename truncating_iterator_base<OutputIt>::value_type;
 
-  truncating_iterator(OutputIt out, std::size_t limit)
+  truncating_iterator(OutputIt out, size_t limit)
       : truncating_iterator_base<OutputIt>(out, limit) {}
 
   truncating_iterator& operator++() {
@@ -456,7 +485,7 @@ template <typename OutputIt>
 class truncating_iterator<OutputIt, std::true_type>
     : public truncating_iterator_base<OutputIt> {
  public:
-  truncating_iterator(OutputIt out, std::size_t limit)
+  truncating_iterator(OutputIt out, size_t limit)
       : truncating_iterator_base<OutputIt>(out, limit) {}
 
   template <typename T> truncating_iterator& operator=(T val) {
@@ -469,22 +498,6 @@ class truncating_iterator<OutputIt, std::true_type>
   truncating_iterator& operator*() { return *this; }
 };
 
-// A range with the specified output iterator and value type.
-template <typename OutputIt, typename T = typename OutputIt::value_type>
-class output_range {
- private:
-  OutputIt it_;
-
- public:
-  using value_type = T;
-  using iterator = OutputIt;
-  struct sentinel {};
-
-  explicit output_range(OutputIt it) : it_(it) {}
-  OutputIt begin() const { return it_; }
-  sentinel end() const { return {}; }  // Sentinel is not used yet.
-};
-
 template <typename Char>
 inline size_t count_code_points(basic_string_view<Char> s) {
   return s.size();
@@ -523,8 +536,6 @@ inline size_t code_point_index(basic_string_view<char8_type> s, size_t n) {
   return s.size();
 }
 
-inline char8_type to_char8_t(char c) { return static_cast<char8_type>(c); }
-
 template <typename InputIt, typename OutChar>
 using needs_conversion = bool_constant<
     std::is_same<typename std::iterator_traits<InputIt>::value_type,
@@ -540,7 +551,8 @@ OutputIt copy_str(InputIt begin, InputIt end, OutputIt it) {
 template <typename OutChar, typename InputIt, typename OutputIt,
           FMT_ENABLE_IF(needs_conversion<InputIt, OutChar>::value)>
 OutputIt copy_str(InputIt begin, InputIt end, OutputIt it) {
-  return std::transform(begin, end, it, to_char8_t);
+  return std::transform(begin, end, it,
+                        [](char c) { return static_cast<char8_type>(c); });
 }
 
 #ifndef FMT_USE_GRISU
@@ -555,43 +567,13 @@ template <typename T> constexpr bool use_grisu() {
 template <typename T>
 template <typename U>
 void buffer<T>::append(const U* begin, const U* end) {
-  std::size_t new_size = size_ + to_unsigned(end - begin);
+  size_t new_size = size_ + to_unsigned(end - begin);
   reserve(new_size);
-  std::uninitialized_copy(begin, end, make_checked(ptr_, capacity_) + size_);
+  std::uninitialized_copy(begin, end,
+                          make_checked(ptr_ + size_, capacity_ - size_));
   size_ = new_size;
 }
-}  // namespace internal
-
-// A range with an iterator appending to a buffer.
-template <typename T>
-class buffer_range : public internal::output_range<
-                         std::back_insert_iterator<internal::buffer<T>>, T> {
- public:
-  using iterator = std::back_insert_iterator<internal::buffer<T>>;
-  using internal::output_range<iterator, T>::output_range;
-  buffer_range(internal::buffer<T>& buf)
-      : internal::output_range<iterator, T>(std::back_inserter(buf)) {}
-};
-
-class FMT_DEPRECATED u8string_view
-    : public basic_string_view<internal::char8_type> {
- public:
-  u8string_view(const char* s)
-      : basic_string_view<internal::char8_type>(
-            reinterpret_cast<const internal::char8_type*>(s)) {}
-  u8string_view(const char* s, size_t count) FMT_NOEXCEPT
-      : basic_string_view<internal::char8_type>(
-            reinterpret_cast<const internal::char8_type*>(s), count) {}
-};
-
-#if FMT_USE_USER_DEFINED_LITERALS
-inline namespace literals {
-FMT_DEPRECATED inline basic_string_view<internal::char8_type> operator"" _u(
-    const char* s, std::size_t n) {
-  return {reinterpret_cast<const internal::char8_type*>(s), n};
-}
-}  // namespace literals
-#endif
+}  // namespace detail
 
 // The number of characters to store in the basic_memory_buffer object itself
 // to avoid dynamic memory allocation.
@@ -626,27 +608,30 @@ enum { inline_buffer_size = 500 };
   The output can be converted to an ``std::string`` with ``to_string(out)``.
   \endrst
  */
-template <typename T, std::size_t SIZE = inline_buffer_size,
+template <typename T, size_t SIZE = inline_buffer_size,
           typename Allocator = std::allocator<T>>
-class basic_memory_buffer : private Allocator, public internal::buffer<T> {
+class basic_memory_buffer : public detail::buffer<T> {
  private:
   T store_[SIZE];
 
+  // Don't inherit from Allocator avoid generating type_info for it.
+  Allocator alloc_;
+
   // Deallocate memory allocated by the buffer.
   void deallocate() {
     T* data = this->data();
-    if (data != store_) Allocator::deallocate(data, this->capacity());
+    if (data != store_) alloc_.deallocate(data, this->capacity());
   }
 
  protected:
-  void grow(std::size_t size) FMT_OVERRIDE;
+  void grow(size_t size) FMT_OVERRIDE;
 
  public:
   using value_type = T;
   using const_reference = const T&;
 
   explicit basic_memory_buffer(const Allocator& alloc = Allocator())
-      : Allocator(alloc) {
+      : alloc_(alloc) {
     this->set(store_, SIZE);
   }
   ~basic_memory_buffer() FMT_OVERRIDE { deallocate(); }
@@ -654,14 +639,13 @@ class basic_memory_buffer : private Allocator, public internal::buffer<T> {
  private:
   // Move data from other to this buffer.
   void move(basic_memory_buffer& other) {
-    Allocator &this_alloc = *this, &other_alloc = other;
-    this_alloc = std::move(other_alloc);
+    alloc_ = std::move(other.alloc_);
     T* data = other.data();
-    std::size_t size = other.size(), capacity = other.capacity();
+    size_t size = other.size(), capacity = other.capacity();
     if (data == other.store_) {
       this->set(store_, capacity);
       std::uninitialized_copy(other.store_, other.store_ + size,
-                              internal::make_checked(store_, capacity));
+                              detail::make_checked(store_, capacity));
     } else {
       this->set(data, capacity);
       // Set pointer to the inline array so that delete is not called
@@ -693,32 +677,37 @@ class basic_memory_buffer : private Allocator, public internal::buffer<T> {
   }
 
   // Returns a copy of the allocator associated with this buffer.
-  Allocator get_allocator() const { return *this; }
+  Allocator get_allocator() const { return alloc_; }
 };
 
-template <typename T, std::size_t SIZE, typename Allocator>
-void basic_memory_buffer<T, SIZE, Allocator>::grow(std::size_t size) {
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-  if (size > 1000) throw std::runtime_error("fuzz mode - won't grow that much");
+template <typename T, size_t SIZE, typename Allocator>
+void basic_memory_buffer<T, SIZE, Allocator>::grow(size_t size) {
+#ifdef FMT_FUZZ
+  if (size > 5000) throw std::runtime_error("fuzz mode - won't grow that much");
 #endif
-  std::size_t old_capacity = this->capacity();
-  std::size_t new_capacity = old_capacity + old_capacity / 2;
+  size_t old_capacity = this->capacity();
+  size_t new_capacity = old_capacity + old_capacity / 2;
   if (size > new_capacity) new_capacity = size;
   T* old_data = this->data();
-  T* new_data = std::allocator_traits<Allocator>::allocate(*this, new_capacity);
+  T* new_data =
+      std::allocator_traits<Allocator>::allocate(alloc_, new_capacity);
   // The following code doesn't throw, so the raw pointer above doesn't leak.
   std::uninitialized_copy(old_data, old_data + this->size(),
-                          internal::make_checked(new_data, new_capacity));
+                          detail::make_checked(new_data, new_capacity));
   this->set(new_data, new_capacity);
   // deallocate must not throw according to the standard, but even if it does,
   // the buffer already uses the new storage and will deallocate it in
   // destructor.
-  if (old_data != store_) Allocator::deallocate(old_data, old_capacity);
+  if (old_data != store_) alloc_.deallocate(old_data, old_capacity);
 }
 
 using memory_buffer = basic_memory_buffer<char>;
 using wmemory_buffer = basic_memory_buffer<wchar_t>;
 
+template <typename T, size_t SIZE, typename Allocator>
+struct is_contiguous<basic_memory_buffer<T, SIZE, Allocator>> : std::true_type {
+};
+
 /** A formatting error such as invalid format string. */
 FMT_CLASS_API
 class FMT_API format_error : public std::runtime_error {
@@ -733,15 +722,20 @@ class FMT_API format_error : public std::runtime_error {
   ~format_error() FMT_NOEXCEPT FMT_OVERRIDE;
 };
 
-namespace internal {
+namespace detail {
+
+template <typename T>
+using is_signed =
+    std::integral_constant<bool, std::numeric_limits<T>::is_signed ||
+                                     std::is_same<T, int128_t>::value>;
 
 // Returns true if value is negative, false otherwise.
 // Same as `value < 0` but doesn't produce warnings if T is an unsigned type.
-template <typename T, FMT_ENABLE_IF(std::numeric_limits<T>::is_signed)>
+template <typename T, FMT_ENABLE_IF(is_signed<T>::value)>
 FMT_CONSTEXPR bool is_negative(T value) {
   return value < 0;
 }
-template <typename T, FMT_ENABLE_IF(!std::numeric_limits<T>::is_signed)>
+template <typename T, FMT_ENABLE_IF(!is_signed<T>::value)>
 FMT_CONSTEXPR bool is_negative(T) {
   return false;
 }
@@ -756,9 +750,9 @@ FMT_CONSTEXPR bool is_supported_floating_point(T) {
 // Smallest of uint32_t, uint64_t, uint128_t that is large enough to
 // represent all values of T.
 template <typename T>
-using uint32_or_64_or_128_t = conditional_t<
-    std::numeric_limits<T>::digits <= 32, uint32_t,
-    conditional_t<std::numeric_limits<T>::digits <= 64, uint64_t, uint128_t>>;
+using uint32_or_64_or_128_t =
+    conditional_t<num_bits<T>() <= 32, uint32_t,
+                  conditional_t<num_bits<T>() <= 64, uint64_t, uint128_t>>;
 
 // Static data is placed in this class template for the header-only config.
 template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
@@ -767,16 +761,22 @@ template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
   static const uint64_t zero_or_powers_of_10_64[];
   static const uint64_t pow10_significands[];
   static const int16_t pow10_exponents[];
-  static const char digits[];
+  // GCC generates slightly better code for pairs than chars.
+  using digit_pair = char[2];
+  static const digit_pair digits[];
   static const char hex_digits[];
   static const char foreground_color[];
   static const char background_color[];
   static const char reset_color[5];
   static const wchar_t wreset_color[5];
   static const char signs[];
+  static const char left_padding_shifts[5];
+  static const char right_padding_shifts[5];
 };
 
+#ifndef FMT_EXPORTED
 FMT_EXTERN template struct basic_data<void>;
+#endif
 
 // This is a struct rather than an alias to avoid shadowing warnings in gcc.
 struct data : basic_data<> {};
@@ -834,7 +834,7 @@ template <unsigned BITS, typename UInt> inline int count_digits(UInt n) {
   return num_digits;
 }
 
-template <> int count_digits<4>(internal::fallback_uintptr n);
+template <> int count_digits<4>(detail::fallback_uintptr n);
 
 #if FMT_GCC_VERSION || FMT_CLANG_VERSION
 #  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
@@ -850,6 +850,12 @@ inline int count_digits(uint32_t n) {
 }
 #endif
 
+template <typename Int> constexpr int digits10() FMT_NOEXCEPT {
+  return std::numeric_limits<Int>::digits10;
+}
+template <> constexpr int digits10<int128_t>() FMT_NOEXCEPT { return 38; }
+template <> constexpr int digits10<uint128_t>() FMT_NOEXCEPT { return 38; }
+
 template <typename Char> FMT_API std::string grouping_impl(locale_ref loc);
 template <typename Char> inline std::string grouping(locale_ref loc) {
   return grouping_impl<char>(loc);
@@ -874,57 +880,61 @@ template <> inline wchar_t decimal_point(locale_ref loc) {
   return decimal_point_impl<wchar_t>(loc);
 }
 
-// Formats a decimal unsigned integer value writing into buffer.
-// add_thousands_sep is called after writing each char to add a thousands
-// separator if necessary.
-template <typename UInt, typename Char, typename F>
-inline Char* format_decimal(Char* buffer, UInt value, int num_digits,
-                            F add_thousands_sep) {
-  FMT_ASSERT(num_digits >= 0, "invalid digit count");
-  buffer += num_digits;
-  Char* end = buffer;
+// Compares two characters for equality.
+template <typename Char> bool equal2(const Char* lhs, const char* rhs) {
+  return lhs[0] == rhs[0] && lhs[1] == rhs[1];
+}
+inline bool equal2(const char* lhs, const char* rhs) {
+  return memcmp(lhs, rhs, 2) == 0;
+}
+
+// Copies two characters from src to dst.
+template <typename Char> void copy2(Char* dst, const char* src) {
+  *dst++ = static_cast<Char>(*src++);
+  *dst = static_cast<Char>(*src);
+}
+inline void copy2(char* dst, const char* src) { memcpy(dst, src, 2); }
+
+template <typename Iterator> struct format_decimal_result {
+  Iterator begin;
+  Iterator end;
+};
+
+// Formats a decimal unsigned integer value writing into out pointing to a
+// buffer of specified size. The caller must ensure that the buffer is large
+// enough.
+template <typename Char, typename UInt>
+inline format_decimal_result<Char*> format_decimal(Char* out, UInt value,
+                                                   int size) {
+  FMT_ASSERT(size >= count_digits(value), "invalid digit count");
+  out += size;
+  Char* end = out;
   while (value >= 100) {
     // Integer division is slow so do it for a group of two digits instead
     // of for every digit. The idea comes from the talk by Alexandrescu
     // "Three Optimization Tips for C++". See speed-test for a comparison.
-    auto index = static_cast<unsigned>((value % 100) * 2);
+    out -= 2;
+    copy2(out, data::digits[value % 100]);
     value /= 100;
-    *--buffer = static_cast<Char>(data::digits[index + 1]);
-    add_thousands_sep(buffer);
-    *--buffer = static_cast<Char>(data::digits[index]);
-    add_thousands_sep(buffer);
   }
   if (value < 10) {
-    *--buffer = static_cast<Char>('0' + value);
-    return end;
+    *--out = static_cast<Char>('0' + value);
+    return {out, end};
   }
-  auto index = static_cast<unsigned>(value * 2);
-  *--buffer = static_cast<Char>(data::digits[index + 1]);
-  add_thousands_sep(buffer);
-  *--buffer = static_cast<Char>(data::digits[index]);
-  return end;
+  out -= 2;
+  copy2(out, data::digits[value]);
+  return {out, end};
 }
 
-template <typename Int> constexpr int digits10() FMT_NOEXCEPT {
-  return std::numeric_limits<Int>::digits10;
-}
-template <> constexpr int digits10<int128_t>() FMT_NOEXCEPT { return 38; }
-template <> constexpr int digits10<uint128_t>() FMT_NOEXCEPT { return 38; }
-
-template <typename Char, typename UInt, typename Iterator, typename F>
-inline Iterator format_decimal(Iterator out, UInt value, int num_digits,
-                               F add_thousands_sep) {
-  FMT_ASSERT(num_digits >= 0, "invalid digit count");
+template <typename Char, typename UInt, typename Iterator,
+          FMT_ENABLE_IF(!std::is_pointer<remove_cvref_t<Iterator>>::value)>
+inline format_decimal_result<Iterator> format_decimal(Iterator out, UInt value,
+                                                      int num_digits) {
   // Buffer should be large enough to hold all digits (<= digits10 + 1).
   enum { max_size = digits10<UInt>() + 1 };
   Char buffer[2 * max_size];
-  auto end = format_decimal(buffer, value, num_digits, add_thousands_sep);
-  return internal::copy_str<Char>(buffer, end, out);
-}
-
-template <typename Char, typename It, typename UInt>
-inline It format_decimal(It out, UInt value, int num_digits) {
-  return format_decimal<Char>(out, value, num_digits, [](Char*) {});
+  auto end = format_decimal(buffer, value, num_digits).end;
+  return {out, detail::copy_str<Char>(buffer, end, out)};
 }
 
 template <unsigned BASE_BITS, typename Char, typename UInt>
@@ -942,7 +952,7 @@ inline Char* format_uint(Char* buffer, UInt value, int num_digits,
 }
 
 template <unsigned BASE_BITS, typename Char>
-Char* format_uint(Char* buffer, internal::fallback_uintptr n, int num_digits,
+Char* format_uint(Char* buffer, detail::fallback_uintptr n, int num_digits,
                   bool = false) {
   auto char_digits = std::numeric_limits<unsigned char>::digits / 4;
   int start = (num_digits + char_digits - 1) / char_digits - 1;
@@ -968,7 +978,7 @@ inline It format_uint(It out, UInt value, int num_digits, bool upper = false) {
   // Buffer should be large enough to hold all digits (digits / BASE_BITS + 1).
   char buffer[num_bits<UInt>() / BASE_BITS + 1];
   format_uint<BASE_BITS>(buffer, value, num_digits, upper);
-  return internal::copy_str<Char>(buffer, buffer + num_digits, out);
+  return detail::copy_str<Char>(buffer, buffer + num_digits, out);
 }
 
 // A converter from UTF-8 to UTF-16.
@@ -1019,7 +1029,7 @@ template <typename Char> struct fill_t {
     return fill;
   }
 };
-}  // namespace internal
+}  // namespace detail
 
 // We cannot use enum classes as bit fields because of a gcc bug
 // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61414.
@@ -1041,7 +1051,7 @@ template <typename Char> struct basic_format_specs {
   align_t align : 4;
   sign_t sign : 3;
   bool alt : 1;  // Alternate form ('#').
-  internal::fill_t<Char> fill;
+  detail::fill_t<Char> fill;
 
   constexpr basic_format_specs()
       : width(0),
@@ -1050,12 +1060,12 @@ template <typename Char> struct basic_format_specs {
         align(align::none),
         sign(sign::none),
         alt(false),
-        fill(internal::fill_t<Char>::make()) {}
+        fill(detail::fill_t<Char>::make()) {}
 };
 
 using format_specs = basic_format_specs<char>;
 
-namespace internal {
+namespace detail {
 
 // A floating-point presentation format.
 enum class float_format : unsigned char {
@@ -1071,7 +1081,6 @@ struct float_specs {
   sign_t sign : 8;
   bool upper : 1;
   bool locale : 1;
-  bool percent : 1;
   bool binary32 : 1;
   bool use_grisu : 1;
   bool showpoint : 1;
@@ -1087,12 +1096,12 @@ template <typename Char, typename It> It write_exponent(int exp, It it) {
     *it++ = static_cast<Char>('+');
   }
   if (exp >= 100) {
-    const char* top = data::digits + (exp / 100) * 2;
+    const char* top = data::digits[exp / 100];
     if (exp >= 1000) *it++ = static_cast<Char>(top[0]);
     *it++ = static_cast<Char>(top[1]);
     exp %= 100;
   }
-  const char* d = data::digits + exp * 2;
+  const char* d = data::digits[exp];
   *it++ = static_cast<Char>(d[0]);
   *it++ = static_cast<Char>(d[1]);
   return it;
@@ -1134,8 +1143,8 @@ template <typename Char> class float_writer {
             *it++ = static_cast<Char>('0');
           return it;
         }
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-        if (num_zeros > 1000)
+#ifdef FMT_FUZZ
+        if (num_zeros > 5000)
           throw std::runtime_error("fuzz mode - avoiding excessive cpu use");
 #endif
         it = std::fill_n(it, num_zeros, static_cast<Char>('0'));
@@ -1198,11 +1207,10 @@ template <typename Char> class float_writer {
   }
 
   size_t size() const { return size_; }
-  size_t width() const { return size(); }
 
-  template <typename It> void operator()(It&& it) {
+  template <typename It> It operator()(It it) const {
     if (specs_.sign) *it++ = static_cast<Char>(data::signs[specs_.sign]);
-    it = prettify(it);
+    return prettify(it);
   }
 };
 
@@ -1235,10 +1243,15 @@ FMT_CONSTEXPR void handle_int_type_spec(char spec, Handler&& handler) {
   case 'o':
     handler.on_oct();
     break;
+#ifdef FMT_DEPRECATED_N_SPECIFIER
   case 'n':
+#endif
   case 'L':
     handler.on_num();
     break;
+  case 'c':
+    handler.on_chr();
+    break;
   default:
     handler.on_error();
   }
@@ -1274,19 +1287,16 @@ FMT_CONSTEXPR float_specs parse_float_type_spec(
     result.format = float_format::fixed;
     result.showpoint |= specs.precision != 0;
     break;
-#if FMT_DEPRECATED_PERCENT
-  case '%':
-    result.format = float_format::fixed;
-    result.percent = true;
-    break;
-#endif
   case 'A':
     result.upper = true;
     FMT_FALLTHROUGH;
   case 'a':
     result.format = float_format::hex;
     break;
+#ifdef FMT_DEPRECATED_N_SPECIFIER
   case 'n':
+#endif
+  case 'L':
     result.locale = true;
     break;
   default:
@@ -1335,6 +1345,7 @@ template <typename ErrorHandler> class int_type_checker : private ErrorHandler {
   FMT_CONSTEXPR void on_bin() {}
   FMT_CONSTEXPR void on_oct() {}
   FMT_CONSTEXPR void on_num() {}
+  FMT_CONSTEXPR void on_chr() {}
 
   FMT_CONSTEXPR void on_error() {
     ErrorHandler::on_error("invalid type specifier");
@@ -1366,38 +1377,6 @@ class cstring_type_checker : public ErrorHandler {
   FMT_CONSTEXPR void on_pointer() {}
 };
 
-template <typename Context>
-void arg_map<Context>::init(const basic_format_args<Context>& args) {
-  if (map_) return;
-  map_ = new entry[internal::to_unsigned(args.max_size())];
-  if (args.is_packed()) {
-    for (int i = 0;; ++i) {
-      internal::type arg_type = args.type(i);
-      if (arg_type == internal::type::none_type) return;
-      if (arg_type == internal::type::named_arg_type)
-        push_back(args.values_[i]);
-    }
-  }
-  for (int i = 0, n = args.max_size(); i < n; ++i) {
-    auto type = args.args_[i].type_;
-    if (type == internal::type::named_arg_type) push_back(args.args_[i].value_);
-  }
-}
-
-template <typename Char> struct nonfinite_writer {
-  sign_t sign;
-  const char* str;
-  static constexpr size_t str_size = 3;
-
-  size_t size() const { return str_size + (sign ? 1 : 0); }
-  size_t width() const { return size(); }
-
-  template <typename It> void operator()(It&& it) const {
-    if (sign) *it++ = static_cast<Char>(data::signs[sign]);
-    it = copy_str<Char>(str, str + str_size, it);
-  }
-};
-
 template <typename OutputIt, typename Char>
 FMT_NOINLINE OutputIt fill(OutputIt it, size_t n, const fill_t<Char>& fill) {
   auto fill_size = fill.size();
@@ -1406,375 +1385,474 @@ FMT_NOINLINE OutputIt fill(OutputIt it, size_t n, const fill_t<Char>& fill) {
   return it;
 }
 
-// This template provides operations for formatting and writing data into a
-// character range.
-template <typename Range> class basic_writer {
- public:
-  using char_type = typename Range::value_type;
-  using iterator = typename Range::iterator;
-  using format_specs = basic_format_specs<char_type>;
+// Writes the output of f, padded according to format specifications in specs.
+// size: output size in code units.
+// width: output display width in (terminal) column positions.
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+inline OutputIt write_padded(OutputIt out,
+                             const basic_format_specs<Char>& specs, size_t size,
+                             size_t width, const F& f) {
+  static_assert(align == align::left || align == align::right, "");
+  unsigned spec_width = to_unsigned(specs.width);
+  size_t padding = spec_width > width ? spec_width - width : 0;
+  auto* shifts = align == align::left ? data::left_padding_shifts
+                                      : data::right_padding_shifts;
+  size_t left_padding = padding >> shifts[specs.align];
+  auto it = reserve(out, size + padding * specs.fill.size());
+  it = fill(it, left_padding, specs.fill);
+  it = f(it);
+  it = fill(it, padding - left_padding, specs.fill);
+  return base_iterator(out, it);
+}
 
- private:
-  iterator out_;  // Output iterator.
-  locale_ref locale_;
+template <align::type align = align::left, typename OutputIt, typename Char,
+          typename F>
+inline OutputIt write_padded(OutputIt out,
+                             const basic_format_specs<Char>& specs, size_t size,
+                             const F& f) {
+  return write_padded<align>(out, specs, size, size, f);
+}
 
-  // Attempts to reserve space for n extra characters in the output range.
-  // Returns a pointer to the reserved range or a reference to out_.
-  auto reserve(std::size_t n) -> decltype(internal::reserve(out_, n)) {
-    return internal::reserve(out_, n);
-  }
+template <typename Char, typename OutputIt>
+OutputIt write_bytes(OutputIt out, string_view bytes,
+                     const basic_format_specs<Char>& specs) {
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, bytes.size(), [bytes](iterator it) {
+    const char* data = bytes.data();
+    return copy_str<Char>(data, data + bytes.size(), it);
+  });
+}
 
-  template <typename F> struct padded_int_writer {
-    size_t size_;
-    string_view prefix;
-    char_type fill;
-    std::size_t padding;
-    F f;
+// Data for write_int that doesn't depend on output iterator type. It is used to
+// avoid template code bloat.
+template <typename Char> struct write_int_data {
+  size_t size;
+  size_t padding;
 
-    size_t size() const { return size_; }
-    size_t width() const { return size_; }
-
-    template <typename It> void operator()(It&& it) const {
-      if (prefix.size() != 0)
-        it = copy_str<char_type>(prefix.begin(), prefix.end(), it);
-      it = std::fill_n(it, padding, fill);
-      f(it);
-    }
-  };
-
-  // Writes an integer in the format
-  //   <left-padding><prefix><numeric-padding><digits><right-padding>
-  // where <digits> are written by f(it).
-  template <typename F>
-  void write_int(int num_digits, string_view prefix, format_specs specs, F f) {
-    std::size_t size = prefix.size() + to_unsigned(num_digits);
-    char_type fill = specs.fill[0];
-    std::size_t padding = 0;
+  write_int_data(int num_digits, string_view prefix,
+                 const basic_format_specs<Char>& specs)
+      : size(prefix.size() + to_unsigned(num_digits)), padding(0) {
     if (specs.align == align::numeric) {
-      auto unsiged_width = to_unsigned(specs.width);
-      if (unsiged_width > size) {
-        padding = unsiged_width - size;
-        size = unsiged_width;
+      auto width = to_unsigned(specs.width);
+      if (width > size) {
+        padding = width - size;
+        size = width;
       }
     } else if (specs.precision > num_digits) {
       size = prefix.size() + to_unsigned(specs.precision);
       padding = to_unsigned(specs.precision - num_digits);
-      fill = static_cast<char_type>('0');
     }
-    if (specs.align == align::none) specs.align = align::right;
-    write_padded(specs, padded_int_writer<F>{size, prefix, fill, padding, f});
+  }
+};
+
+// Writes an integer in the format
+//   <left-padding><prefix><numeric-padding><digits><right-padding>
+// where <digits> are written by f(it).
+template <typename OutputIt, typename Char, typename F>
+OutputIt write_int(OutputIt out, int num_digits, string_view prefix,
+                   const basic_format_specs<Char>& specs, F f) {
+  auto data = write_int_data<Char>(num_digits, prefix, specs);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded<align::right>(out, specs, data.size, [=](iterator it) {
+    if (prefix.size() != 0)
+      it = copy_str<Char>(prefix.begin(), prefix.end(), it);
+    it = std::fill_n(it, data.padding, static_cast<Char>('0'));
+    return f(it);
+  });
+}
+
+template <typename StrChar, typename Char, typename OutputIt>
+OutputIt write(OutputIt out, basic_string_view<StrChar> s,
+               const basic_format_specs<Char>& specs) {
+  auto data = s.data();
+  auto size = s.size();
+  if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
+    size = code_point_index(s, to_unsigned(specs.precision));
+  auto width = specs.width != 0
+                   ? count_code_points(basic_string_view<StrChar>(data, size))
+                   : 0;
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, size, width, [=](iterator it) {
+    return copy_str<Char>(data, data + size, it);
+  });
+}
+
+// The handle_int_type_spec handler that writes an integer.
+template <typename OutputIt, typename Char, typename UInt> struct int_writer {
+  OutputIt out;
+  locale_ref locale;
+  const basic_format_specs<Char>& specs;
+  UInt abs_value;
+  char prefix[4];
+  unsigned prefix_size;
+
+  using iterator =
+      remove_reference_t<decltype(reserve(std::declval<OutputIt&>(), 0))>;
+
+  string_view get_prefix() const { return string_view(prefix, prefix_size); }
+
+  template <typename Int>
+  int_writer(OutputIt output, locale_ref loc, Int value,
+             const basic_format_specs<Char>& s)
+      : out(output),
+        locale(loc),
+        specs(s),
+        abs_value(static_cast<UInt>(value)),
+        prefix_size(0) {
+    static_assert(std::is_same<uint32_or_64_or_128_t<Int>, UInt>::value, "");
+    if (is_negative(value)) {
+      prefix[0] = '-';
+      ++prefix_size;
+      abs_value = 0 - abs_value;
+    } else if (specs.sign != sign::none && specs.sign != sign::minus) {
+      prefix[0] = specs.sign == sign::plus ? '+' : ' ';
+      ++prefix_size;
+    }
   }
 
-  // Writes a decimal integer.
-  template <typename Int> void write_decimal(Int value) {
-    auto abs_value = static_cast<uint32_or_64_or_128_t<Int>>(value);
-    bool negative = is_negative(value);
-    // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
-    if (negative) abs_value = ~abs_value + 1;
+  void on_dec() {
+    auto num_digits = count_digits(abs_value);
+    out = write_int(
+        out, num_digits, get_prefix(), specs, [this, num_digits](iterator it) {
+          return format_decimal<Char>(it, abs_value, num_digits).end;
+        });
+  }
+
+  void on_hex() {
+    if (specs.alt) {
+      prefix[prefix_size++] = '0';
+      prefix[prefix_size++] = specs.type;
+    }
+    int num_digits = count_digits<4>(abs_value);
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<4, Char>(it, abs_value, num_digits,
+                                                  specs.type != 'x');
+                    });
+  }
+
+  void on_bin() {
+    if (specs.alt) {
+      prefix[prefix_size++] = '0';
+      prefix[prefix_size++] = static_cast<char>(specs.type);
+    }
+    int num_digits = count_digits<1>(abs_value);
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<1, Char>(it, abs_value, num_digits);
+                    });
+  }
+
+  void on_oct() {
+    int num_digits = count_digits<3>(abs_value);
+    if (specs.alt && specs.precision <= num_digits && abs_value != 0) {
+      // Octal prefix '0' is counted as a digit, so only add it if precision
+      // is not greater than the number of digits.
+      prefix[prefix_size++] = '0';
+    }
+    out = write_int(out, num_digits, get_prefix(), specs,
+                    [this, num_digits](iterator it) {
+                      return format_uint<3, Char>(it, abs_value, num_digits);
+                    });
+  }
+
+  enum { sep_size = 1 };
+
+  void on_num() {
+    std::string groups = grouping<Char>(locale);
+    if (groups.empty()) return on_dec();
+    auto sep = thousands_sep<Char>(locale);
+    if (!sep) return on_dec();
     int num_digits = count_digits(abs_value);
-    auto&& it = reserve((negative ? 1 : 0) + static_cast<size_t>(num_digits));
-    if (negative) *it++ = static_cast<char_type>('-');
-    it = format_decimal<char_type>(it, abs_value, num_digits);
-  }
-
-  // The handle_int_type_spec handler that writes an integer.
-  template <typename Int, typename Specs> struct int_writer {
-    using unsigned_type = uint32_or_64_or_128_t<Int>;
-
-    basic_writer<Range>& writer;
-    const Specs& specs;
-    unsigned_type abs_value;
-    char prefix[4];
-    unsigned prefix_size;
-
-    string_view get_prefix() const { return string_view(prefix, prefix_size); }
-
-    int_writer(basic_writer<Range>& w, Int value, const Specs& s)
-        : writer(w),
-          specs(s),
-          abs_value(static_cast<unsigned_type>(value)),
-          prefix_size(0) {
-      if (is_negative(value)) {
-        prefix[0] = '-';
-        ++prefix_size;
-        abs_value = 0 - abs_value;
-      } else if (specs.sign != sign::none && specs.sign != sign::minus) {
-        prefix[0] = specs.sign == sign::plus ? '+' : ' ';
-        ++prefix_size;
-      }
+    int size = num_digits, n = num_digits;
+    std::string::const_iterator group = groups.cbegin();
+    while (group != groups.cend() && n > *group && *group > 0 &&
+           *group != max_value<char>()) {
+      size += sep_size;
+      n -= *group;
+      ++group;
     }
-
-    struct dec_writer {
-      unsigned_type abs_value;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = internal::format_decimal<char_type>(it, abs_value, num_digits);
-      }
-    };
-
-    void on_dec() {
-      int num_digits = count_digits(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       dec_writer{abs_value, num_digits});
-    }
-
-    struct hex_writer {
-      int_writer& self;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = format_uint<4, char_type>(it, self.abs_value, num_digits,
-                                       self.specs.type != 'x');
-      }
-    };
-
-    void on_hex() {
-      if (specs.alt) {
-        prefix[prefix_size++] = '0';
-        prefix[prefix_size++] = specs.type;
-      }
-      int num_digits = count_digits<4>(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       hex_writer{*this, num_digits});
-    }
-
-    template <int BITS> struct bin_writer {
-      unsigned_type abs_value;
-      int num_digits;
-
-      template <typename It> void operator()(It&& it) const {
-        it = format_uint<BITS, char_type>(it, abs_value, num_digits);
-      }
-    };
-
-    void on_bin() {
-      if (specs.alt) {
-        prefix[prefix_size++] = '0';
-        prefix[prefix_size++] = static_cast<char>(specs.type);
-      }
-      int num_digits = count_digits<1>(abs_value);
-      writer.write_int(num_digits, get_prefix(), specs,
-                       bin_writer<1>{abs_value, num_digits});
-    }
-
-    void on_oct() {
-      int num_digits = count_digits<3>(abs_value);
-      if (specs.alt && specs.precision <= num_digits && abs_value != 0) {
-        // Octal prefix '0' is counted as a digit, so only add it if precision
-        // is not greater than the number of digits.
-        prefix[prefix_size++] = '0';
-      }
-      writer.write_int(num_digits, get_prefix(), specs,
-                       bin_writer<3>{abs_value, num_digits});
-    }
-
-    enum { sep_size = 1 };
-
-    struct num_writer {
-      unsigned_type abs_value;
-      int size;
-      const std::string& groups;
-      char_type sep;
-
-      template <typename It> void operator()(It&& it) const {
-        basic_string_view<char_type> s(&sep, sep_size);
-        // Index of a decimal digit with the least significant digit having
-        // index 0.
-        int digit_index = 0;
-        std::string::const_iterator group = groups.cbegin();
-        it = format_decimal<char_type>(
-            it, abs_value, size,
-            [this, s, &group, &digit_index](char_type*& buffer) {
-              if (*group <= 0 || ++digit_index % *group != 0 ||
-                  *group == max_value<char>())
-                return;
-              if (group + 1 != groups.cend()) {
-                digit_index = 0;
-                ++group;
-              }
-              buffer -= s.size();
-              std::uninitialized_copy(s.data(), s.data() + s.size(),
-                                      make_checked(buffer, s.size()));
-            });
-      }
-    };
-
-    void on_num() {
-      std::string groups = grouping<char_type>(writer.locale_);
-      if (groups.empty()) return on_dec();
-      auto sep = thousands_sep<char_type>(writer.locale_);
-      if (!sep) return on_dec();
-      int num_digits = count_digits(abs_value);
-      int size = num_digits;
-      std::string::const_iterator group = groups.cbegin();
-      while (group != groups.cend() && num_digits > *group && *group > 0 &&
-             *group != max_value<char>()) {
-        size += sep_size;
-        num_digits -= *group;
+    if (group == groups.cend()) size += sep_size * ((n - 1) / groups.back());
+    char digits[40];
+    format_decimal(digits, abs_value, num_digits);
+    basic_memory_buffer<Char> buffer;
+    size += prefix_size;
+    buffer.resize(size);
+    basic_string_view<Char> s(&sep, sep_size);
+    // Index of a decimal digit with the least significant digit having index 0.
+    int digit_index = 0;
+    group = groups.cbegin();
+    auto p = buffer.data() + size;
+    for (int i = num_digits - 1; i >= 0; --i) {
+      *--p = static_cast<Char>(digits[i]);
+      if (*group <= 0 || ++digit_index % *group != 0 ||
+          *group == max_value<char>())
+        continue;
+      if (group + 1 != groups.cend()) {
+        digit_index = 0;
         ++group;
       }
-      if (group == groups.cend())
-        size += sep_size * ((num_digits - 1) / groups.back());
-      writer.write_int(size, get_prefix(), specs,
-                       num_writer{abs_value, size, groups, sep});
+      p -= s.size();
+      std::uninitialized_copy(s.data(), s.data() + s.size(),
+                              make_checked(p, s.size()));
     }
+    if (prefix_size != 0) p[-1] = static_cast<Char>('-');
+    using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+    auto data = buffer.data();
+    out = write_padded<align::right>(out, specs, size, size, [=](iterator it) {
+      return copy_str<Char>(data, data + size, it);
+    });
+  }
 
-    FMT_NORETURN void on_error() {
-      FMT_THROW(format_error("invalid type specifier"));
-    }
+  void on_chr() { *out++ = static_cast<Char>(abs_value); }
+
+  FMT_NORETURN void on_error() {
+    FMT_THROW(format_error("invalid type specifier"));
+  }
+};
+
+template <typename Char, typename OutputIt>
+OutputIt write_nonfinite(OutputIt out, bool isinf,
+                         const basic_format_specs<Char>& specs,
+                         const float_specs& fspecs) {
+  auto str =
+      isinf ? (fspecs.upper ? "INF" : "inf") : (fspecs.upper ? "NAN" : "nan");
+  constexpr size_t str_size = 3;
+  auto sign = fspecs.sign;
+  auto size = str_size + (sign ? 1 : 0);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, size, [=](iterator it) {
+    if (sign) *it++ = static_cast<Char>(data::signs[sign]);
+    return copy_str<Char>(str, str + str_size, it);
+  });
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+OutputIt write(OutputIt out, T value, basic_format_specs<Char> specs,
+               locale_ref loc = {}) {
+  if (const_check(!is_supported_floating_point(value))) return out;
+  float_specs fspecs = parse_float_type_spec(specs);
+  fspecs.sign = specs.sign;
+  if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
+    fspecs.sign = sign::minus;
+    value = -value;
+  } else if (fspecs.sign == sign::minus) {
+    fspecs.sign = sign::none;
+  }
+
+  if (!std::isfinite(value))
+    return write_nonfinite(out, std::isinf(value), specs, fspecs);
+
+  if (specs.align == align::numeric && fspecs.sign) {
+    auto it = reserve(out, 1);
+    *it++ = static_cast<Char>(data::signs[fspecs.sign]);
+    out = base_iterator(out, it);
+    fspecs.sign = sign::none;
+    if (specs.width != 0) --specs.width;
+  }
+
+  memory_buffer buffer;
+  if (fspecs.format == float_format::hex) {
+    if (fspecs.sign) buffer.push_back(data::signs[fspecs.sign]);
+    snprintf_float(promote_float(value), specs.precision, fspecs, buffer);
+    return write_bytes(out, {buffer.data(), buffer.size()}, specs);
+  }
+  int precision = specs.precision >= 0 || !specs.type ? specs.precision : 6;
+  if (fspecs.format == float_format::exp) {
+    if (precision == max_value<int>())
+      FMT_THROW(format_error("number is too big"));
+    else
+      ++precision;
+  }
+  if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
+  fspecs.use_grisu = use_grisu<T>();
+  int exp = format_float(promote_float(value), precision, fspecs, buffer);
+  fspecs.precision = precision;
+  Char point =
+      fspecs.locale ? decimal_point<Char>(loc) : static_cast<Char>('.');
+  float_writer<Char> w(buffer.data(), static_cast<int>(buffer.size()), exp,
+                       fspecs, point);
+  return write_padded<align::right>(out, specs, w.size(), w);
+}
+
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+OutputIt write(OutputIt out, T value) {
+  if (const_check(!is_supported_floating_point(value))) return out;
+  auto fspecs = float_specs();
+  if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
+    fspecs.sign = sign::minus;
+    value = -value;
+  }
+
+  auto specs = basic_format_specs<Char>();
+  if (!std::isfinite(value))
+    return write_nonfinite(out, std::isinf(value), specs, fspecs);
+
+  memory_buffer buffer;
+  int precision = -1;
+  if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
+  fspecs.use_grisu = use_grisu<T>();
+  int exp = format_float(promote_float(value), precision, fspecs, buffer);
+  fspecs.precision = precision;
+  float_writer<Char> w(buffer.data(), static_cast<int>(buffer.size()), exp,
+                       fspecs, static_cast<Char>('.'));
+  return base_iterator(out, w(reserve(out, w.size())));
+}
+
+template <typename Char, typename OutputIt>
+OutputIt write_char(OutputIt out, Char value,
+                    const basic_format_specs<Char>& specs) {
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  return write_padded(out, specs, 1, [=](iterator it) {
+    *it++ = value;
+    return it;
+  });
+}
+
+template <typename Char, typename OutputIt, typename UIntPtr>
+OutputIt write_ptr(OutputIt out, UIntPtr value,
+                   const basic_format_specs<Char>* specs) {
+  int num_digits = count_digits<4>(value);
+  auto size = to_unsigned(num_digits) + size_t(2);
+  using iterator = remove_reference_t<decltype(reserve(out, 0))>;
+  auto write = [=](iterator it) {
+    *it++ = static_cast<Char>('0');
+    *it++ = static_cast<Char>('x');
+    return format_uint<4, Char>(it, value, num_digits);
   };
+  return specs ? write_padded<align::right>(out, *specs, size, write)
+               : base_iterator(out, write(reserve(out, size)));
+}
 
-  template <typename Char> struct str_writer {
-    const Char* s;
-    size_t size_;
+template <typename T> struct is_integral : std::is_integral<T> {};
+template <> struct is_integral<int128_t> : std::true_type {};
+template <> struct is_integral<uint128_t> : std::true_type {};
 
-    size_t size() const { return size_; }
-    size_t width() const {
-      return count_code_points(basic_string_view<Char>(s, size_));
-    }
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, monostate) {
+  FMT_ASSERT(false, "");
+  return out;
+}
 
-    template <typename It> void operator()(It&& it) const {
-      it = copy_str<char_type>(s, s + size_, it);
-    }
-  };
+template <typename Char, typename OutputIt,
+          FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
+OutputIt write(OutputIt out, string_view value) {
+  auto it = reserve(out, value.size());
+  it = copy_str<Char>(value.begin(), value.end(), it);
+  return base_iterator(out, it);
+}
 
-  struct bytes_writer {
-    string_view bytes;
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, basic_string_view<Char> value) {
+  auto it = reserve(out, value.size());
+  it = std::copy(value.begin(), value.end(), it);
+  return base_iterator(out, it);
+}
 
-    size_t size() const { return bytes.size(); }
-    size_t width() const { return bytes.size(); }
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(is_integral<T>::value &&
+                        !std::is_same<T, bool>::value &&
+                        !std::is_same<T, Char>::value)>
+OutputIt write(OutputIt out, T value) {
+  auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
+  bool negative = is_negative(value);
+  // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
+  if (negative) abs_value = ~abs_value + 1;
+  int num_digits = count_digits(abs_value);
+  auto it = reserve(out, (negative ? 1 : 0) + static_cast<size_t>(num_digits));
+  if (negative) *it++ = static_cast<Char>('-');
+  it = format_decimal<Char>(it, abs_value, num_digits).end;
+  return base_iterator(out, it);
+}
 
-    template <typename It> void operator()(It&& it) const {
-      const char* data = bytes.data();
-      it = copy_str<char>(data, data + size(), it);
-    }
-  };
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, bool value) {
+  return write<Char>(out, string_view(value ? "true" : "false"));
+}
 
-  template <typename UIntPtr> struct pointer_writer {
-    UIntPtr value;
-    int num_digits;
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, Char value) {
+  auto it = reserve(out, 1);
+  *it++ = value;
+  return base_iterator(out, it);
+}
 
-    size_t size() const { return to_unsigned(num_digits) + 2; }
-    size_t width() const { return size(); }
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, const Char* value) {
+  if (!value) {
+    FMT_THROW(format_error("string pointer is null"));
+  } else {
+    auto length = std::char_traits<Char>::length(value);
+    out = write(out, basic_string_view<Char>(value, length));
+  }
+  return out;
+}
 
-    template <typename It> void operator()(It&& it) const {
-      *it++ = static_cast<char_type>('0');
-      *it++ = static_cast<char_type>('x');
-      it = format_uint<4, char_type>(it, value, num_digits);
-    }
-  };
+template <typename Char, typename OutputIt>
+OutputIt write(OutputIt out, const void* value) {
+  return write_ptr<Char>(out, to_uintptr(value), nullptr);
+}
 
+template <typename Char, typename OutputIt, typename T>
+auto write(OutputIt out, const T& value) -> typename std::enable_if<
+    mapped_type_constant<T, basic_format_context<OutputIt, Char>>::value ==
+        type::custom_type,
+    OutputIt>::type {
+  basic_format_context<OutputIt, Char> ctx(out, {}, {});
+  return formatter<T>().format(value, ctx);
+}
+
+// An argument visitor that formats the argument and writes it via the output
+// iterator. It's a class and not a generic lambda for compatibility with C++11.
+template <typename OutputIt, typename Char> struct default_arg_formatter {
+  using context = basic_format_context<OutputIt, Char>;
+
+  OutputIt out;
+  basic_format_args<context> args;
+  locale_ref loc;
+
+  template <typename T> OutputIt operator()(T value) {
+    return write<Char>(out, value);
+  }
+
+  OutputIt operator()(typename basic_format_arg<context>::handle handle) {
+    basic_format_parse_context<Char> parse_ctx({});
+    basic_format_context<OutputIt, Char> format_ctx(out, args, loc);
+    handle.format(parse_ctx, format_ctx);
+    return format_ctx.out();
+  }
+};
+
+template <typename OutputIt, typename Char,
+          typename ErrorHandler = error_handler>
+class arg_formatter_base {
  public:
-  explicit basic_writer(Range out, locale_ref loc = locale_ref())
-      : out_(out.begin()), locale_(loc) {}
+  using iterator = OutputIt;
+  using char_type = Char;
+  using format_specs = basic_format_specs<Char>;
 
-  iterator out() const { return out_; }
+ private:
+  iterator out_;
+  locale_ref locale_;
+  format_specs* specs_;
 
-  // Writes a value in the format
-  //   <left-padding><value><right-padding>
-  // where <value> is written by f(it).
-  template <typename F> void write_padded(const format_specs& specs, F&& f) {
-    // User-perceived width (in code points).
-    unsigned width = to_unsigned(specs.width);
-    size_t size = f.size();  // The number of code units.
-    size_t num_code_points = width != 0 ? f.width() : size;
-    if (width <= num_code_points) return f(reserve(size));
-    size_t padding = width - num_code_points;
-    size_t fill_size = specs.fill.size();
-    auto&& it = reserve(size + padding * fill_size);
-    if (specs.align == align::right) {
-      it = fill(it, padding, specs.fill);
-      f(it);
-    } else if (specs.align == align::center) {
-      std::size_t left_padding = padding / 2;
-      it = fill(it, left_padding, specs.fill);
-      f(it);
-      it = fill(it, padding - left_padding, specs.fill);
-    } else {
-      f(it);
-      it = fill(it, padding, specs.fill);
-    }
+  // Attempts to reserve space for n extra characters in the output range.
+  // Returns a pointer to the reserved range or a reference to out_.
+  auto reserve(size_t n) -> decltype(detail::reserve(out_, n)) {
+    return detail::reserve(out_, n);
   }
 
-  void write(int value) { write_decimal(value); }
-  void write(long value) { write_decimal(value); }
-  void write(long long value) { write_decimal(value); }
+  using reserve_iterator = remove_reference_t<decltype(
+      detail::reserve(std::declval<iterator&>(), 0))>;
 
-  void write(unsigned value) { write_decimal(value); }
-  void write(unsigned long value) { write_decimal(value); }
-  void write(unsigned long long value) { write_decimal(value); }
-
-#if FMT_USE_INT128
-  void write(int128_t value) { write_decimal(value); }
-  void write(uint128_t value) { write_decimal(value); }
-#endif
-
-  template <typename T, typename Spec>
-  void write_int(T value, const Spec& spec) {
-    handle_int_type_spec(spec.type, int_writer<T, Spec>(*this, value, spec));
-  }
-
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  void write(T value, format_specs specs = {}) {
-    if (const_check(!is_supported_floating_point(value))) {
-      return;
-    }
-    float_specs fspecs = parse_float_type_spec(specs);
-    fspecs.sign = specs.sign;
-    if (std::signbit(value)) {  // value < 0 is false for NaN so use signbit.
-      fspecs.sign = sign::minus;
-      value = -value;
-    } else if (fspecs.sign == sign::minus) {
-      fspecs.sign = sign::none;
-    }
-
-    if (!std::isfinite(value)) {
-      auto str = std::isinf(value) ? (fspecs.upper ? "INF" : "inf")
-                                   : (fspecs.upper ? "NAN" : "nan");
-      return write_padded(specs, nonfinite_writer<char_type>{fspecs.sign, str});
-    }
-
-    if (specs.align == align::none) {
-      specs.align = align::right;
-    } else if (specs.align == align::numeric) {
-      if (fspecs.sign) {
-        auto&& it = reserve(1);
-        *it++ = static_cast<char_type>(data::signs[fspecs.sign]);
-        fspecs.sign = sign::none;
-        if (specs.width != 0) --specs.width;
-      }
-      specs.align = align::right;
-    }
-
-    memory_buffer buffer;
-    if (fspecs.format == float_format::hex) {
-      if (fspecs.sign) buffer.push_back(data::signs[fspecs.sign]);
-      snprintf_float(promote_float(value), specs.precision, fspecs, buffer);
-      write_padded(specs, str_writer<char>{buffer.data(), buffer.size()});
-      return;
-    }
-    int precision = specs.precision >= 0 || !specs.type ? specs.precision : 6;
-    if (fspecs.format == float_format::exp) {
-      if (precision == max_value<int>())
-        FMT_THROW(format_error("number is too big"));
-      else
-        ++precision;
-    }
-    if (const_check(std::is_same<T, float>())) fspecs.binary32 = true;
-    fspecs.use_grisu = use_grisu<T>();
-    if (const_check(FMT_DEPRECATED_PERCENT) && fspecs.percent) value *= 100;
-    int exp = format_float(promote_float(value), precision, fspecs, buffer);
-    if (const_check(FMT_DEPRECATED_PERCENT) && fspecs.percent) {
-      buffer.push_back('%');
-      --exp;  // Adjust decimal place position.
-    }
-    fspecs.precision = precision;
-    char_type point = fspecs.locale ? decimal_point<char_type>(locale_)
-                                    : static_cast<char_type>('.');
-    write_padded(specs, float_writer<char_type>(buffer.data(),
-                                                static_cast<int>(buffer.size()),
-                                                exp, fspecs, point));
+  template <typename T> void write_int(T value, const format_specs& spec) {
+    using uint_type = uint32_or_64_or_128_t<T>;
+    int_writer<iterator, Char, uint_type> w(out_, locale_, value, spec);
+    handle_int_type_spec(spec.type, w);
+    out_ = w.out;
   }
 
   void write(char value) {
@@ -1782,198 +1860,151 @@ template <typename Range> class basic_writer {
     *it++ = value;
   }
 
-  template <typename Char, FMT_ENABLE_IF(std::is_same<Char, char_type>::value)>
-  void write(Char value) {
-    auto&& it = reserve(1);
-    *it++ = value;
+  template <typename Ch, FMT_ENABLE_IF(std::is_same<Ch, Char>::value)>
+  void write(Ch value) {
+    out_ = detail::write<Char>(out_, value);
   }
 
   void write(string_view value) {
     auto&& it = reserve(value.size());
-    it = copy_str<char_type>(value.begin(), value.end(), it);
+    it = copy_str<Char>(value.begin(), value.end(), it);
   }
   void write(wstring_view value) {
-    static_assert(std::is_same<char_type, wchar_t>::value, "");
+    static_assert(std::is_same<Char, wchar_t>::value, "");
     auto&& it = reserve(value.size());
     it = std::copy(value.begin(), value.end(), it);
   }
 
-  template <typename Char>
-  void write(const Char* s, std::size_t size, const format_specs& specs) {
-    write_padded(specs, str_writer<Char>{s, size});
+  template <typename Ch>
+  void write(const Ch* s, size_t size, const format_specs& specs) {
+    auto width = specs.width != 0
+                     ? count_code_points(basic_string_view<Ch>(s, size))
+                     : 0;
+    out_ = write_padded(out_, specs, size, width, [=](reserve_iterator it) {
+      return copy_str<Char>(s, s + size, it);
+    });
   }
 
-  template <typename Char>
-  void write(basic_string_view<Char> s, const format_specs& specs = {}) {
-    const Char* data = s.data();
-    std::size_t size = s.size();
-    if (specs.precision >= 0 && to_unsigned(specs.precision) < size)
-      size = code_point_index(s, to_unsigned(specs.precision));
-    write(data, size, specs);
-  }
-
-  void write_bytes(string_view bytes, const format_specs& specs) {
-    write_padded(specs, bytes_writer{bytes});
-  }
-
-  template <typename UIntPtr>
-  void write_pointer(UIntPtr value, const format_specs* specs) {
-    int num_digits = count_digits<4>(value);
-    auto pw = pointer_writer<UIntPtr>{value, num_digits};
-    if (!specs) return pw(reserve(to_unsigned(num_digits) + 2));
-    format_specs specs_copy = *specs;
-    if (specs_copy.align == align::none) specs_copy.align = align::right;
-    write_padded(specs_copy, pw);
-  }
-};
-
-using writer = basic_writer<buffer_range<char>>;
-
-template <typename T> struct is_integral : std::is_integral<T> {};
-template <> struct is_integral<int128_t> : std::true_type {};
-template <> struct is_integral<uint128_t> : std::true_type {};
-
-template <typename Range, typename ErrorHandler = internal::error_handler>
-class arg_formatter_base {
- public:
-  using char_type = typename Range::value_type;
-  using iterator = typename Range::iterator;
-  using format_specs = basic_format_specs<char_type>;
-
- private:
-  using writer_type = basic_writer<Range>;
-  writer_type writer_;
-  format_specs* specs_;
-
-  struct char_writer {
-    char_type value;
-
-    size_t size() const { return 1; }
-    size_t width() const { return 1; }
-
-    template <typename It> void operator()(It&& it) const { *it++ = value; }
-  };
-
-  void write_char(char_type value) {
-    if (specs_)
-      writer_.write_padded(*specs_, char_writer{value});
-    else
-      writer_.write(value);
+  template <typename Ch>
+  void write(basic_string_view<Ch> s, const format_specs& specs = {}) {
+    out_ = detail::write(out_, s, specs);
   }
 
   void write_pointer(const void* p) {
-    writer_.write_pointer(internal::to_uintptr(p), specs_);
-  }
-
- protected:
-  writer_type& writer() { return writer_; }
-  FMT_DEPRECATED format_specs* spec() { return specs_; }
-  format_specs* specs() { return specs_; }
-  iterator out() { return writer_.out(); }
-
-  void write(bool value) {
-    string_view sv(value ? "true" : "false");
-    specs_ ? writer_.write(sv, *specs_) : writer_.write(sv);
-  }
-
-  void write(const char_type* value) {
-    if (!value) {
-      FMT_THROW(format_error("string pointer is null"));
-    } else {
-      auto length = std::char_traits<char_type>::length(value);
-      basic_string_view<char_type> sv(value, length);
-      specs_ ? writer_.write(sv, *specs_) : writer_.write(sv);
-    }
-  }
-
- public:
-  arg_formatter_base(Range r, format_specs* s, locale_ref loc)
-      : writer_(r, loc), specs_(s) {}
-
-  iterator operator()(monostate) {
-    FMT_ASSERT(false, "invalid argument type");
-    return out();
-  }
-
-  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)>
-  iterator operator()(T value) {
-    if (specs_)
-      writer_.write_int(value, *specs_);
-    else
-      writer_.write(value);
-    return out();
-  }
-
-  iterator operator()(char_type value) {
-    internal::handle_char_specs(
-        specs_, char_spec_handler(*this, static_cast<char_type>(value)));
-    return out();
-  }
-
-  iterator operator()(bool value) {
-    if (specs_ && specs_->type) return (*this)(value ? 1 : 0);
-    write(value != 0);
-    return out();
-  }
-
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  iterator operator()(T value) {
-    if (const_check(is_supported_floating_point(value)))
-      writer_.write(value, specs_ ? *specs_ : format_specs());
-    else
-      FMT_ASSERT(false, "unsupported float argument type");
-    return out();
+    out_ = write_ptr<char_type>(out_, to_uintptr(p), specs_);
   }
 
   struct char_spec_handler : ErrorHandler {
     arg_formatter_base& formatter;
-    char_type value;
+    Char value;
 
-    char_spec_handler(arg_formatter_base& f, char_type val)
+    char_spec_handler(arg_formatter_base& f, Char val)
         : formatter(f), value(val) {}
 
     void on_int() {
-      if (formatter.specs_)
-        formatter.writer_.write_int(value, *formatter.specs_);
-      else
-        formatter.writer_.write(value);
+      // char is only formatted as int if there are specs.
+      formatter.write_int(static_cast<int>(value), *formatter.specs_);
+    }
+    void on_char() {
+      if (formatter.specs_)
+        formatter.out_ = write_char(formatter.out_, value, *formatter.specs_);
+      else
+        formatter.write(value);
     }
-    void on_char() { formatter.write_char(value); }
   };
 
-  struct cstring_spec_handler : internal::error_handler {
+  struct cstring_spec_handler : error_handler {
     arg_formatter_base& formatter;
-    const char_type* value;
+    const Char* value;
 
-    cstring_spec_handler(arg_formatter_base& f, const char_type* val)
+    cstring_spec_handler(arg_formatter_base& f, const Char* val)
         : formatter(f), value(val) {}
 
     void on_string() { formatter.write(value); }
     void on_pointer() { formatter.write_pointer(value); }
   };
 
-  iterator operator()(const char_type* value) {
-    if (!specs_) return write(value), out();
-    internal::handle_cstring_type_spec(specs_->type,
-                                       cstring_spec_handler(*this, value));
-    return out();
+ protected:
+  iterator out() { return out_; }
+  format_specs* specs() { return specs_; }
+
+  void write(bool value) {
+    if (specs_)
+      write(string_view(value ? "true" : "false"), *specs_);
+    else
+      out_ = detail::write<Char>(out_, value);
   }
 
-  iterator operator()(basic_string_view<char_type> value) {
-    if (specs_) {
-      internal::check_string_type_spec(specs_->type, internal::error_handler());
-      writer_.write(value, *specs_);
+  void write(const Char* value) {
+    if (!value) {
+      FMT_THROW(format_error("string pointer is null"));
     } else {
-      writer_.write(value);
+      auto length = std::char_traits<char_type>::length(value);
+      basic_string_view<char_type> sv(value, length);
+      specs_ ? write(sv, *specs_) : write(sv);
     }
-    return out();
+  }
+
+ public:
+  arg_formatter_base(OutputIt out, format_specs* s, locale_ref loc)
+      : out_(out), locale_(loc), specs_(s) {}
+
+  iterator operator()(monostate) {
+    FMT_ASSERT(false, "invalid argument type");
+    return out_;
+  }
+
+  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)>
+  FMT_INLINE iterator operator()(T value) {
+    if (specs_)
+      write_int(value, *specs_);
+    else
+      out_ = detail::write<Char>(out_, value);
+    return out_;
+  }
+
+  iterator operator()(Char value) {
+    handle_char_specs(specs_,
+                      char_spec_handler(*this, static_cast<Char>(value)));
+    return out_;
+  }
+
+  iterator operator()(bool value) {
+    if (specs_ && specs_->type) return (*this)(value ? 1 : 0);
+    write(value != 0);
+    return out_;
+  }
+
+  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
+  iterator operator()(T value) {
+    auto specs = specs_ ? *specs_ : format_specs();
+    if (const_check(is_supported_floating_point(value)))
+      out_ = detail::write(out_, value, specs, locale_);
+    else
+      FMT_ASSERT(false, "unsupported float argument type");
+    return out_;
+  }
+
+  iterator operator()(const Char* value) {
+    if (!specs_) return write(value), out_;
+    handle_cstring_type_spec(specs_->type, cstring_spec_handler(*this, value));
+    return out_;
+  }
+
+  iterator operator()(basic_string_view<Char> value) {
+    if (specs_) {
+      check_string_type_spec(specs_->type, error_handler());
+      write(value, *specs_);
+    } else {
+      write(value);
+    }
+    return out_;
   }
 
   iterator operator()(const void* value) {
-    if (specs_)
-      check_pointer_type_spec(specs_->type, internal::error_handler());
+    if (specs_) check_pointer_type_spec(specs_->type, error_handler());
     write_pointer(value);
-    return out();
+    return out_;
   }
 };
 
@@ -2109,7 +2140,7 @@ template <typename Char> class specs_setter {
 
 template <typename ErrorHandler> class numeric_specs_checker {
  public:
-  FMT_CONSTEXPR numeric_specs_checker(ErrorHandler& eh, internal::type arg_type)
+  FMT_CONSTEXPR numeric_specs_checker(ErrorHandler& eh, detail::type arg_type)
       : error_handler_(eh), arg_type_(arg_type) {}
 
   FMT_CONSTEXPR void require_numeric_argument() {
@@ -2132,18 +2163,24 @@ template <typename ErrorHandler> class numeric_specs_checker {
 
  private:
   ErrorHandler& error_handler_;
-  internal::type arg_type_;
+  detail::type arg_type_;
 };
 
 // A format specifier handler that checks if specifiers are consistent with the
 // argument type.
 template <typename Handler> class specs_checker : public Handler {
+ private:
+  numeric_specs_checker<Handler> checker_;
+
+  // Suppress an MSVC warning about using this in initializer list.
+  FMT_CONSTEXPR Handler& error_handler() { return *this; }
+
  public:
-  FMT_CONSTEXPR specs_checker(const Handler& handler, internal::type arg_type)
-      : Handler(handler), checker_(*this, arg_type) {}
+  FMT_CONSTEXPR specs_checker(const Handler& handler, detail::type arg_type)
+      : Handler(handler), checker_(error_handler(), arg_type) {}
 
   FMT_CONSTEXPR specs_checker(const specs_checker& other)
-      : Handler(other), checker_(*this, other.arg_type_) {}
+      : Handler(other), checker_(error_handler(), other.arg_type_) {}
 
   FMT_CONSTEXPR void on_align(align_t align) {
     if (align == align::numeric) checker_.require_numeric_argument();
@@ -2176,9 +2213,6 @@ template <typename Handler> class specs_checker : public Handler {
   }
 
   FMT_CONSTEXPR void end_precision() { checker_.check_precision(); }
-
- private:
-  numeric_specs_checker<Handler> checker_;
 };
 
 template <template <typename> class Handler, typename FormatArg,
@@ -2191,10 +2225,10 @@ FMT_CONSTEXPR int get_dynamic_spec(FormatArg arg, ErrorHandler eh) {
 
 struct auto_id {};
 
-template <typename Context>
-FMT_CONSTEXPR typename Context::format_arg get_arg(Context& ctx, int id) {
+template <typename Context, typename ID>
+FMT_CONSTEXPR typename Context::format_arg get_arg(Context& ctx, ID id) {
   auto arg = ctx.arg(id);
-  if (!arg) ctx.on_error("argument index out of range");
+  if (!arg) ctx.on_error("argument not found");
   return arg;
 }
 
@@ -2227,17 +2261,17 @@ class specs_handler : public specs_setter<typename Context::char_type> {
   using format_arg = typename Context::format_arg;
 
   FMT_CONSTEXPR format_arg get_arg(auto_id) {
-    return internal::get_arg(context_, parse_context_.next_arg_id());
+    return detail::get_arg(context_, parse_context_.next_arg_id());
   }
 
   FMT_CONSTEXPR format_arg get_arg(int arg_id) {
     parse_context_.check_arg_id(arg_id);
-    return internal::get_arg(context_, arg_id);
+    return detail::get_arg(context_, arg_id);
   }
 
   FMT_CONSTEXPR format_arg get_arg(basic_string_view<char_type> arg_id) {
     parse_context_.check_arg_id(arg_id);
-    return context_.arg(arg_id);
+    return detail::get_arg(context_, arg_id);
   }
 
   ParseContext& parse_context_;
@@ -2424,7 +2458,7 @@ FMT_CONSTEXPR const Char* parse_align(const Char* begin, const Char* end,
     case '>':
       align = align::right;
       break;
-#if FMT_NUMERIC_ALIGN
+#if FMT_DEPRECATED_NUMERIC_ALIGN
     case '=':
       align = align::numeric;
       break;
@@ -2555,26 +2589,75 @@ template <>
 inline bool find<false, char>(const char* first, const char* last, char value,
                               const char*& out) {
   out = static_cast<const char*>(
-      std::memchr(first, value, internal::to_unsigned(last - first)));
+      std::memchr(first, value, detail::to_unsigned(last - first)));
   return out != nullptr;
 }
 
 template <typename Handler, typename Char> struct id_adapter {
-  FMT_CONSTEXPR void operator()() { handler.on_arg_id(); }
-  FMT_CONSTEXPR void operator()(int id) { handler.on_arg_id(id); }
+  Handler& handler;
+  int arg_id;
+
+  FMT_CONSTEXPR void operator()() { arg_id = handler.on_arg_id(); }
+  FMT_CONSTEXPR void operator()(int id) { arg_id = handler.on_arg_id(id); }
   FMT_CONSTEXPR void operator()(basic_string_view<Char> id) {
-    handler.on_arg_id(id);
+    arg_id = handler.on_arg_id(id);
   }
   FMT_CONSTEXPR void on_error(const char* message) {
     handler.on_error(message);
   }
-  Handler& handler;
 };
 
+template <typename Char, typename Handler>
+FMT_CONSTEXPR const Char* parse_replacement_field(const Char* begin,
+                                                  const Char* end,
+                                                  Handler&& handler) {
+  ++begin;
+  if (begin == end) return handler.on_error("invalid format string"), end;
+  if (static_cast<char>(*begin) == '}') {
+    handler.on_replacement_field(handler.on_arg_id(), begin);
+  } else if (*begin == '{') {
+    handler.on_text(begin, begin + 1);
+  } else {
+    auto adapter = id_adapter<Handler, Char>{handler, 0};
+    begin = parse_arg_id(begin, end, adapter);
+    Char c = begin != end ? *begin : Char();
+    if (c == '}') {
+      handler.on_replacement_field(adapter.arg_id, begin);
+    } else if (c == ':') {
+      begin = handler.on_format_specs(adapter.arg_id, begin + 1, end);
+      if (begin == end || *begin != '}')
+        return handler.on_error("unknown format specifier"), end;
+    } else {
+      return handler.on_error("missing '}' in format string"), end;
+    }
+  }
+  return begin + 1;
+}
+
 template <bool IS_CONSTEXPR, typename Char, typename Handler>
-FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
-                                       Handler&& handler) {
-  struct pfs_writer {
+FMT_CONSTEXPR_DECL FMT_INLINE void parse_format_string(
+    basic_string_view<Char> format_str, Handler&& handler) {
+  auto begin = format_str.data();
+  auto end = begin + format_str.size();
+  if (end - begin < 32) {
+    // Use a simple loop instead of memchr for small strings.
+    const Char* p = begin;
+    while (p != end) {
+      auto c = *p++;
+      if (c == '{') {
+        handler.on_text(begin, p - 1);
+        begin = p = parse_replacement_field(p - 1, end, handler);
+      } else if (c == '}') {
+        if (p == end || *p != '}')
+          return handler.on_error("unmatched '}' in format string");
+        handler.on_text(begin, p);
+        begin = ++p;
+      }
+    }
+    handler.on_text(begin, end);
+    return;
+  }
+  struct writer {
     FMT_CONSTEXPR void operator()(const Char* begin, const Char* end) {
       if (begin == end) return;
       for (;;) {
@@ -2590,8 +2673,6 @@ FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
     }
     Handler& handler_;
   } write{handler};
-  auto begin = format_str.data();
-  auto end = begin + format_str.size();
   while (begin != end) {
     // Doing two passes with memchr (one for '{' and another for '}') is up to
     // 2.5x faster than the naive one-pass implementation on big format strings.
@@ -2599,27 +2680,7 @@ FMT_CONSTEXPR void parse_format_string(basic_string_view<Char> format_str,
     if (*begin != '{' && !find<IS_CONSTEXPR>(begin + 1, end, '{', p))
       return write(begin, end);
     write(begin, p);
-    ++p;
-    if (p == end) return handler.on_error("invalid format string");
-    if (static_cast<char>(*p) == '}') {
-      handler.on_arg_id();
-      handler.on_replacement_field(p);
-    } else if (*p == '{') {
-      handler.on_text(p, p + 1);
-    } else {
-      p = parse_arg_id(p, end, id_adapter<Handler, Char>{handler});
-      Char c = p != end ? *p : Char();
-      if (c == '}') {
-        handler.on_replacement_field(p);
-      } else if (c == ':') {
-        p = handler.on_format_specs(p + 1, end);
-        if (p == end || *p != '}')
-          return handler.on_error("unknown format specifier");
-      } else {
-        return handler.on_error("missing '}' in format string");
-      }
-    }
-    begin = p + 1;
+    begin = parse_replacement_field(p, end, handler);
   }
 }
 
@@ -2629,44 +2690,121 @@ FMT_CONSTEXPR const typename ParseContext::char_type* parse_format_specs(
   using char_type = typename ParseContext::char_type;
   using context = buffer_context<char_type>;
   using mapped_type =
-      conditional_t<internal::mapped_type_constant<T, context>::value !=
+      conditional_t<detail::mapped_type_constant<T, context>::value !=
                         type::custom_type,
                     decltype(arg_mapper<context>().map(std::declval<T>())), T>;
   auto f = conditional_t<has_formatter<mapped_type, context>::value,
                          formatter<mapped_type, char_type>,
-                         internal::fallback_formatter<T, char_type>>();
+                         detail::fallback_formatter<T, char_type>>();
   return f.parse(ctx);
 }
 
+template <typename ArgFormatter, typename Char, typename Context>
+struct format_handler : detail::error_handler {
+  basic_format_parse_context<Char> parse_context;
+  Context context;
+
+  format_handler(typename ArgFormatter::iterator out,
+                 basic_string_view<Char> str,
+                 basic_format_args<Context> format_args, detail::locale_ref loc)
+      : parse_context(str), context(out, format_args, loc) {}
+
+  void on_text(const Char* begin, const Char* end) {
+    auto size = to_unsigned(end - begin);
+    auto out = context.out();
+    auto&& it = reserve(out, size);
+    it = std::copy_n(begin, size, it);
+    context.advance_to(out);
+  }
+
+  int on_arg_id() { return parse_context.next_arg_id(); }
+  int on_arg_id(int id) { return parse_context.check_arg_id(id), id; }
+  int on_arg_id(basic_string_view<Char> id) {
+    int arg_id = context.arg_id(id);
+    if (arg_id < 0) on_error("argument not found");
+    return arg_id;
+  }
+
+  FMT_INLINE void on_replacement_field(int id, const Char*) {
+    auto arg = get_arg(context, id);
+    context.advance_to(visit_format_arg(
+        default_arg_formatter<typename ArgFormatter::iterator, Char>{
+            context.out(), context.args(), context.locale()},
+        arg));
+  }
+
+  const Char* on_format_specs(int id, const Char* begin, const Char* end) {
+    advance_to(parse_context, begin);
+    auto arg = get_arg(context, id);
+    custom_formatter<Context> f(parse_context, context);
+    if (visit_format_arg(f, arg)) return parse_context.begin();
+    basic_format_specs<Char> specs;
+    using parse_context_t = basic_format_parse_context<Char>;
+    specs_checker<specs_handler<parse_context_t, Context>> handler(
+        specs_handler<parse_context_t, Context>(specs, parse_context, context),
+        arg.type());
+    begin = parse_format_specs(begin, end, handler);
+    if (begin == end || *begin != '}') on_error("missing '}' in format string");
+    advance_to(parse_context, begin);
+    context.advance_to(
+        visit_format_arg(ArgFormatter(context, &parse_context, &specs), arg));
+    return begin;
+  }
+};
+
+// A parse context with extra argument id checks. It is only used at compile
+// time because adding checks at runtime would introduce substantial overhead
+// and would be redundant since argument ids are checked when arguments are
+// retrieved anyway.
+template <typename Char, typename ErrorHandler = error_handler>
+class compile_parse_context
+    : public basic_format_parse_context<Char, ErrorHandler> {
+ private:
+  int num_args_;
+  using base = basic_format_parse_context<Char, ErrorHandler>;
+
+ public:
+  explicit FMT_CONSTEXPR compile_parse_context(
+      basic_string_view<Char> format_str, int num_args = max_value<int>(),
+      ErrorHandler eh = {})
+      : base(format_str, eh), num_args_(num_args) {}
+
+  FMT_CONSTEXPR int next_arg_id() {
+    int id = base::next_arg_id();
+    if (id >= num_args_) this->on_error("argument not found");
+    return id;
+  }
+
+  FMT_CONSTEXPR void check_arg_id(int id) {
+    base::check_arg_id(id);
+    if (id >= num_args_) this->on_error("argument not found");
+  }
+  using base::check_arg_id;
+};
+
 template <typename Char, typename ErrorHandler, typename... Args>
 class format_string_checker {
  public:
   explicit FMT_CONSTEXPR format_string_checker(
       basic_string_view<Char> format_str, ErrorHandler eh)
-      : arg_id_(-1),
-        context_(format_str, eh),
+      : context_(format_str, num_args, eh),
         parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
 
   FMT_CONSTEXPR void on_text(const Char*, const Char*) {}
 
-  FMT_CONSTEXPR void on_arg_id() {
-    arg_id_ = context_.next_arg_id();
-    check_arg_id();
-  }
-  FMT_CONSTEXPR void on_arg_id(int id) {
-    arg_id_ = id;
-    context_.check_arg_id(id);
-    check_arg_id();
-  }
-  FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) {
+  FMT_CONSTEXPR int on_arg_id() { return context_.next_arg_id(); }
+  FMT_CONSTEXPR int on_arg_id(int id) { return context_.check_arg_id(id), id; }
+  FMT_CONSTEXPR int on_arg_id(basic_string_view<Char>) {
     on_error("compile-time checks don't support named arguments");
+    return 0;
   }
 
-  FMT_CONSTEXPR void on_replacement_field(const Char*) {}
+  FMT_CONSTEXPR void on_replacement_field(int, const Char*) {}
 
-  FMT_CONSTEXPR const Char* on_format_specs(const Char* begin, const Char*) {
+  FMT_CONSTEXPR const Char* on_format_specs(int id, const Char* begin,
+                                            const Char*) {
     advance_to(context_, begin);
-    return arg_id_ < num_args ? parse_funcs_[arg_id_](context_) : begin;
+    return id < num_args ? parse_funcs_[id](context_) : begin;
   }
 
   FMT_CONSTEXPR void on_error(const char* message) {
@@ -2674,35 +2812,66 @@ class format_string_checker {
   }
 
  private:
-  using parse_context_type = basic_format_parse_context<Char, ErrorHandler>;
+  using parse_context_type = compile_parse_context<Char, ErrorHandler>;
   enum { num_args = sizeof...(Args) };
 
-  FMT_CONSTEXPR void check_arg_id() {
-    if (arg_id_ >= num_args) context_.on_error("argument index out of range");
-  }
-
   // Format specifier parsing function.
   using parse_func = const Char* (*)(parse_context_type&);
 
-  int arg_id_;
   parse_context_type context_;
   parse_func parse_funcs_[num_args > 0 ? num_args : 1];
 };
 
-template <typename Char, typename ErrorHandler, typename... Args>
-FMT_CONSTEXPR bool do_check_format_string(basic_string_view<Char> s,
-                                          ErrorHandler eh = ErrorHandler()) {
-  format_string_checker<Char, ErrorHandler, Args...> checker(s, eh);
-  parse_format_string<true>(s, checker);
-  return true;
+// Converts string literals to basic_string_view.
+template <typename Char, size_t N>
+FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
+    const Char (&s)[N]) {
+  // Remove trailing null character if needed. Won't be present if this is used
+  // with raw character array (i.e. not defined as a string).
+  return {s,
+          N - ((std::char_traits<Char>::to_int_type(s[N - 1]) == 0) ? 1 : 0)};
 }
 
+// Converts string_view to basic_string_view.
+template <typename Char>
+FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
+    const std_string_view<Char>& s) {
+  return {s.data(), s.size()};
+}
+
+#define FMT_STRING_IMPL(s, base)                                  \
+  [] {                                                            \
+    /* Use a macro-like name to avoid shadowing warnings. */      \
+    struct FMT_COMPILE_STRING : base {                            \
+      using char_type = fmt::remove_cvref_t<decltype(s[0])>;      \
+      FMT_MAYBE_UNUSED FMT_CONSTEXPR                              \
+      operator fmt::basic_string_view<char_type>() const {        \
+        return fmt::detail::compile_string_to_view<char_type>(s); \
+      }                                                           \
+    };                                                            \
+    return FMT_COMPILE_STRING();                                  \
+  }()
+
+/**
+  \rst
+  Constructs a compile-time format string from a string literal *s*.
+
+  **Example**::
+
+    // A compile-time error because 'd' is an invalid specifier for strings.
+    std::string s = fmt::format(FMT_STRING("{:d}"), "foo");
+  \endrst
+ */
+#define FMT_STRING(s) FMT_STRING_IMPL(s, fmt::compile_string)
+
 template <typename... Args, typename S,
           enable_if_t<(is_compile_string<S>::value), int>>
 void check_format_string(S format_str) {
-  FMT_CONSTEXPR_DECL bool invalid_format = internal::do_check_format_string<
-      typename S::char_type, internal::error_handler,
-      remove_const_t<remove_reference_t<Args>>...>(to_string_view(format_str));
+  FMT_CONSTEXPR_DECL auto s = to_string_view(format_str);
+  using checker = format_string_checker<typename S::char_type, error_handler,
+                                        remove_cvref_t<Args>...>;
+  FMT_CONSTEXPR_DECL bool invalid_format =
+      (parse_format_string<true>(s, checker(s, {})), true);
   (void)invalid_format;
 }
 
@@ -2713,44 +2882,37 @@ void handle_dynamic_spec(int& value, arg_ref<typename Context::char_type> ref,
   case arg_id_kind::none:
     break;
   case arg_id_kind::index:
-    value = internal::get_dynamic_spec<Handler>(ctx.arg(ref.val.index),
-                                                ctx.error_handler());
+    value = detail::get_dynamic_spec<Handler>(ctx.arg(ref.val.index),
+                                              ctx.error_handler());
     break;
   case arg_id_kind::name:
-    value = internal::get_dynamic_spec<Handler>(ctx.arg(ref.val.name),
-                                                ctx.error_handler());
+    value = detail::get_dynamic_spec<Handler>(ctx.arg(ref.val.name),
+                                              ctx.error_handler());
     break;
   }
 }
 
-using format_func = void (*)(internal::buffer<char>&, int, string_view);
+using format_func = void (*)(detail::buffer<char>&, int, string_view);
 
 FMT_API void format_error_code(buffer<char>& out, int error_code,
                                string_view message) FMT_NOEXCEPT;
 
 FMT_API void report_error(format_func func, int error_code,
                           string_view message) FMT_NOEXCEPT;
-}  // namespace internal
-
-template <typename Range>
-using basic_writer FMT_DEPRECATED_ALIAS = internal::basic_writer<Range>;
-using writer FMT_DEPRECATED_ALIAS = internal::writer;
-using wwriter FMT_DEPRECATED_ALIAS =
-    internal::basic_writer<buffer_range<wchar_t>>;
 
 /** The default argument formatter. */
-template <typename Range>
-class arg_formatter : public internal::arg_formatter_base<Range> {
+template <typename OutputIt, typename Char>
+class arg_formatter : public arg_formatter_base<OutputIt, Char> {
  private:
-  using char_type = typename Range::value_type;
-  using base = internal::arg_formatter_base<Range>;
-  using context_type = basic_format_context<typename base::iterator, char_type>;
+  using char_type = Char;
+  using base = arg_formatter_base<OutputIt, Char>;
+  using context_type = basic_format_context<OutputIt, Char>;
 
   context_type& ctx_;
   basic_format_parse_context<char_type>* parse_ctx_;
+  const Char* ptr_;
 
  public:
-  using range = Range;
   using iterator = typename base::iterator;
   using format_specs = typename base::format_specs;
 
@@ -2764,19 +2926,26 @@ class arg_formatter : public internal::arg_formatter_base<Range> {
   explicit arg_formatter(
       context_type& ctx,
       basic_format_parse_context<char_type>* parse_ctx = nullptr,
-      format_specs* specs = nullptr)
-      : base(Range(ctx.out()), specs, ctx.locale()),
+      format_specs* specs = nullptr, const Char* ptr = nullptr)
+      : base(ctx.out(), specs, ctx.locale()),
         ctx_(ctx),
-        parse_ctx_(parse_ctx) {}
+        parse_ctx_(parse_ctx),
+        ptr_(ptr) {}
 
   using base::operator();
 
   /** Formats an argument of a user-defined type. */
   iterator operator()(typename basic_format_arg<context_type>::handle handle) {
+    if (ptr_) advance_to(*parse_ctx_, ptr_);
     handle.format(*parse_ctx_, ctx_);
     return ctx_.out();
   }
 };
+}  // namespace detail
+
+template <typename OutputIt, typename Char>
+using arg_formatter FMT_DEPRECATED_ALIAS =
+  detail::arg_formatter<OutputIt, Char>;
 
 /**
  An error returned by an operating system or a language runtime,
@@ -2841,7 +3010,7 @@ class FMT_API system_error : public std::runtime_error {
   may look like "Unknown error -1" and is platform-dependent.
   \endrst
  */
-FMT_API void format_system_error(internal::buffer<char>& out, int error_code,
+FMT_API void format_system_error(detail::buffer<char>& out, int error_code,
                                  string_view message) FMT_NOEXCEPT;
 
 // Reports a system error without throwing an exception.
@@ -2858,47 +3027,32 @@ class format_int {
   mutable char buffer_[buffer_size];
   char* str_;
 
-  // Formats value in reverse and returns a pointer to the beginning.
-  char* format_decimal(unsigned long long value) {
-    char* ptr = buffer_ + (buffer_size - 1);  // Parens to workaround MSVC bug.
-    while (value >= 100) {
-      // Integer division is slow so do it for a group of two digits instead
-      // of for every digit. The idea comes from the talk by Alexandrescu
-      // "Three Optimization Tips for C++". See speed-test for a comparison.
-      auto index = static_cast<unsigned>((value % 100) * 2);
-      value /= 100;
-      *--ptr = internal::data::digits[index + 1];
-      *--ptr = internal::data::digits[index];
-    }
-    if (value < 10) {
-      *--ptr = static_cast<char>('0' + value);
-      return ptr;
-    }
-    auto index = static_cast<unsigned>(value * 2);
-    *--ptr = internal::data::digits[index + 1];
-    *--ptr = internal::data::digits[index];
-    return ptr;
+  template <typename UInt> char* format_unsigned(UInt value) {
+    auto n = static_cast<detail::uint32_or_64_or_128_t<UInt>>(value);
+    return detail::format_decimal(buffer_, n, buffer_size - 1).begin;
   }
 
-  void format_signed(long long value) {
-    auto abs_value = static_cast<unsigned long long>(value);
+  template <typename Int> char* format_signed(Int value) {
+    auto abs_value = static_cast<detail::uint32_or_64_or_128_t<Int>>(value);
     bool negative = value < 0;
     if (negative) abs_value = 0 - abs_value;
-    str_ = format_decimal(abs_value);
-    if (negative) *--str_ = '-';
+    auto begin = format_unsigned(abs_value);
+    if (negative) *--begin = '-';
+    return begin;
   }
 
  public:
-  explicit format_int(int value) { format_signed(value); }
-  explicit format_int(long value) { format_signed(value); }
-  explicit format_int(long long value) { format_signed(value); }
-  explicit format_int(unsigned value) : str_(format_decimal(value)) {}
-  explicit format_int(unsigned long value) : str_(format_decimal(value)) {}
-  explicit format_int(unsigned long long value) : str_(format_decimal(value)) {}
+  explicit format_int(int value) : str_(format_signed(value)) {}
+  explicit format_int(long value) : str_(format_signed(value)) {}
+  explicit format_int(long long value) : str_(format_signed(value)) {}
+  explicit format_int(unsigned value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long value) : str_(format_unsigned(value)) {}
+  explicit format_int(unsigned long long value)
+      : str_(format_unsigned(value)) {}
 
   /** Returns the number of characters written to the output buffer. */
-  std::size_t size() const {
-    return internal::to_unsigned(buffer_ - str_ + buffer_size - 1);
+  size_t size() const {
+    return detail::to_unsigned(buffer_ - str_ + buffer_size - 1);
   }
 
   /**
@@ -2924,75 +3078,71 @@ class format_int {
   std::string str() const { return std::string(str_, size()); }
 };
 
-// A formatter specialization for the core types corresponding to internal::type
+// A formatter specialization for the core types corresponding to detail::type
 // constants.
 template <typename T, typename Char>
 struct formatter<T, Char,
-                 enable_if_t<internal::type_constant<T, Char>::value !=
-                             internal::type::custom_type>> {
+                 enable_if_t<detail::type_constant<T, Char>::value !=
+                             detail::type::custom_type>> {
   FMT_CONSTEXPR formatter() = default;
 
   // Parses format specifiers stopping either at the end of the range or at the
   // terminating '}'.
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    using handler_type = internal::dynamic_specs_handler<ParseContext>;
-    auto type = internal::type_constant<T, Char>::value;
-    internal::specs_checker<handler_type> handler(handler_type(specs_, ctx),
-                                                  type);
+    using handler_type = detail::dynamic_specs_handler<ParseContext>;
+    auto type = detail::type_constant<T, Char>::value;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+                                                type);
     auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
     auto eh = ctx.error_handler();
     switch (type) {
-    case internal::type::none_type:
-    case internal::type::named_arg_type:
+    case detail::type::none_type:
       FMT_ASSERT(false, "invalid argument type");
       break;
-    case internal::type::int_type:
-    case internal::type::uint_type:
-    case internal::type::long_long_type:
-    case internal::type::ulong_long_type:
-    case internal::type::int128_type:
-    case internal::type::uint128_type:
-    case internal::type::bool_type:
+    case detail::type::int_type:
+    case detail::type::uint_type:
+    case detail::type::long_long_type:
+    case detail::type::ulong_long_type:
+    case detail::type::int128_type:
+    case detail::type::uint128_type:
+    case detail::type::bool_type:
       handle_int_type_spec(specs_.type,
-                           internal::int_type_checker<decltype(eh)>(eh));
+                           detail::int_type_checker<decltype(eh)>(eh));
       break;
-    case internal::type::char_type:
+    case detail::type::char_type:
       handle_char_specs(
-          &specs_, internal::char_specs_checker<decltype(eh)>(specs_.type, eh));
+          &specs_, detail::char_specs_checker<decltype(eh)>(specs_.type, eh));
       break;
-    case internal::type::float_type:
-      if (internal::const_check(FMT_USE_FLOAT)) {
-        internal::parse_float_type_spec(specs_, eh);
-      } else {
+    case detail::type::float_type:
+      if (detail::const_check(FMT_USE_FLOAT))
+        detail::parse_float_type_spec(specs_, eh);
+      else
         FMT_ASSERT(false, "float support disabled");
-      }
       break;
-    case internal::type::double_type:
-      if (internal::const_check(FMT_USE_DOUBLE)) {
-        internal::parse_float_type_spec(specs_, eh);
-      } else {
+    case detail::type::double_type:
+      if (detail::const_check(FMT_USE_DOUBLE))
+        detail::parse_float_type_spec(specs_, eh);
+      else
         FMT_ASSERT(false, "double support disabled");
-      }
       break;
-    case internal::type::long_double_type:
-      if (internal::const_check(FMT_USE_LONG_DOUBLE)) {
-        internal::parse_float_type_spec(specs_, eh);
-      } else {
+    case detail::type::long_double_type:
+      if (detail::const_check(FMT_USE_LONG_DOUBLE))
+        detail::parse_float_type_spec(specs_, eh);
+      else
         FMT_ASSERT(false, "long double support disabled");
-      }
       break;
-    case internal::type::cstring_type:
-      internal::handle_cstring_type_spec(
-          specs_.type, internal::cstring_type_checker<decltype(eh)>(eh));
+    case detail::type::cstring_type:
+      detail::handle_cstring_type_spec(
+          specs_.type, detail::cstring_type_checker<decltype(eh)>(eh));
       break;
-    case internal::type::string_type:
-      internal::check_string_type_spec(specs_.type, eh);
+    case detail::type::string_type:
+      detail::check_string_type_spec(specs_.type, eh);
       break;
-    case internal::type::pointer_type:
-      internal::check_pointer_type_spec(specs_.type, eh);
+    case detail::type::pointer_type:
+      detail::check_pointer_type_spec(specs_.type, eh);
       break;
-    case internal::type::custom_type:
+    case detail::type::custom_type:
       // Custom format specifiers should be checked in parse functions of
       // formatter specializations.
       break;
@@ -3002,19 +3152,18 @@ struct formatter<T, Char,
 
   template <typename FormatContext>
   auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
-    using range_type =
-        internal::output_range<typename FormatContext::iterator,
-                               typename FormatContext::char_type>;
-    return visit_format_arg(arg_formatter<range_type>(ctx, nullptr, &specs_),
-                            internal::make_arg<FormatContext>(val));
+    using af = detail::arg_formatter<typename FormatContext::iterator,
+                                     typename FormatContext::char_type>;
+    return visit_format_arg(af(ctx, nullptr, &specs_),
+                            detail::make_arg<FormatContext>(val));
   }
 
  private:
-  internal::dynamic_format_specs<Char> specs_;
+  detail::dynamic_format_specs<Char> specs_;
 };
 
 #define FMT_FORMAT_AS(Type, Base)                                             \
@@ -3035,7 +3184,7 @@ FMT_FORMAT_AS(unsigned long, unsigned long long);
 FMT_FORMAT_AS(Char*, const Char*);
 FMT_FORMAT_AS(std::basic_string<Char>, basic_string_view<Char>);
 FMT_FORMAT_AS(std::nullptr_t, const void*);
-FMT_FORMAT_AS(internal::std_string_view<Char>, basic_string_view<Char>);
+FMT_FORMAT_AS(detail::std_string_view<Char>, basic_string_view<Char>);
 
 template <typename Char>
 struct formatter<void*, Char> : formatter<const void*, Char> {
@@ -3065,7 +3214,7 @@ struct formatter<Char[N], Char> : formatter<basic_string_view<Char>, Char> {
 //   };
 template <typename Char = char> class dynamic_formatter {
  private:
-  struct null_handler : internal::error_handler {
+  struct null_handler : detail::error_handler {
     void on_align(align_t) {}
     void on_plus() {}
     void on_minus() {}
@@ -3078,16 +3227,15 @@ template <typename Char = char> class dynamic_formatter {
   auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
     format_str_ = ctx.begin();
     // Checks are deferred to formatting time when the argument type is known.
-    internal::dynamic_specs_handler<ParseContext> handler(specs_, ctx);
+    detail::dynamic_specs_handler<ParseContext> handler(specs_, ctx);
     return parse_format_specs(ctx.begin(), ctx.end(), handler);
   }
 
   template <typename T, typename FormatContext>
   auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
     handle_specs(ctx);
-    internal::specs_checker<null_handler> checker(
-        null_handler(),
-        internal::mapped_type_constant<T, FormatContext>::value);
+    detail::specs_checker<null_handler> checker(
+        null_handler(), detail::mapped_type_constant<T, FormatContext>::value);
     checker.on_align(specs_.align);
     switch (specs_.sign) {
     case sign::none:
@@ -3104,104 +3252,47 @@ template <typename Char = char> class dynamic_formatter {
     }
     if (specs_.alt) checker.on_hash();
     if (specs_.precision >= 0) checker.end_precision();
-    using range = internal::output_range<typename FormatContext::iterator,
-                                         typename FormatContext::char_type>;
-    visit_format_arg(arg_formatter<range>(ctx, nullptr, &specs_),
-                     internal::make_arg<FormatContext>(val));
+    using af = detail::arg_formatter<typename FormatContext::iterator,
+                                     typename FormatContext::char_type>;
+    visit_format_arg(af(ctx, nullptr, &specs_),
+                     detail::make_arg<FormatContext>(val));
     return ctx.out();
   }
 
  private:
   template <typename Context> void handle_specs(Context& ctx) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
   }
 
-  internal::dynamic_format_specs<Char> specs_;
+  detail::dynamic_format_specs<Char> specs_;
   const Char* format_str_;
 };
 
-template <typename Range, typename Char>
-typename basic_format_context<Range, Char>::format_arg
-basic_format_context<Range, Char>::arg(basic_string_view<char_type> name) {
-  map_.init(args_);
-  format_arg arg = map_.find(name);
-  if (arg.type() == internal::type::none_type)
-    this->on_error("argument not found");
-  return arg;
-}
-
 template <typename Char, typename ErrorHandler>
 FMT_CONSTEXPR void advance_to(
     basic_format_parse_context<Char, ErrorHandler>& ctx, const Char* p) {
   ctx.advance_to(ctx.begin() + (p - &*ctx.begin()));
 }
 
-template <typename ArgFormatter, typename Char, typename Context>
-struct format_handler : internal::error_handler {
-  using range = typename ArgFormatter::range;
-
-  format_handler(range r, basic_string_view<Char> str,
-                 basic_format_args<Context> format_args,
-                 internal::locale_ref loc)
-      : parse_context(str), context(r.begin(), format_args, loc) {}
-
-  void on_text(const Char* begin, const Char* end) {
-    auto size = internal::to_unsigned(end - begin);
-    auto out = context.out();
-    auto&& it = internal::reserve(out, size);
-    it = std::copy_n(begin, size, it);
-    context.advance_to(out);
-  }
-
-  void get_arg(int id) { arg = internal::get_arg(context, id); }
-
-  void on_arg_id() { get_arg(parse_context.next_arg_id()); }
-  void on_arg_id(int id) {
-    parse_context.check_arg_id(id);
-    get_arg(id);
-  }
-  void on_arg_id(basic_string_view<Char> id) { arg = context.arg(id); }
-
-  void on_replacement_field(const Char* p) {
-    advance_to(parse_context, p);
-    context.advance_to(
-        visit_format_arg(ArgFormatter(context, &parse_context), arg));
-  }
-
-  const Char* on_format_specs(const Char* begin, const Char* end) {
-    advance_to(parse_context, begin);
-    internal::custom_formatter<Context> f(parse_context, context);
-    if (visit_format_arg(f, arg)) return parse_context.begin();
-    basic_format_specs<Char> specs;
-    using internal::specs_handler;
-    using parse_context_t = basic_format_parse_context<Char>;
-    internal::specs_checker<specs_handler<parse_context_t, Context>> handler(
-        specs_handler<parse_context_t, Context>(specs, parse_context, context),
-        arg.type());
-    begin = parse_format_specs(begin, end, handler);
-    if (begin == end || *begin != '}') on_error("missing '}' in format string");
-    advance_to(parse_context, begin);
-    context.advance_to(
-        visit_format_arg(ArgFormatter(context, &parse_context, &specs), arg));
-    return begin;
-  }
-
-  basic_format_parse_context<Char> parse_context;
-  Context context;
-  basic_format_arg<Context> arg;
-};
-
 /** Formats arguments and writes the output to the range. */
 template <typename ArgFormatter, typename Char, typename Context>
 typename Context::iterator vformat_to(
-    typename ArgFormatter::range out, basic_string_view<Char> format_str,
+    typename ArgFormatter::iterator out, basic_string_view<Char> format_str,
     basic_format_args<Context> args,
-    internal::locale_ref loc = internal::locale_ref()) {
-  format_handler<ArgFormatter, Char, Context> h(out, format_str, args, loc);
-  internal::parse_format_string<false>(format_str, h);
+    detail::locale_ref loc = detail::locale_ref()) {
+  if (format_str.size() == 2 && detail::equal2(format_str.data(), "{}")) {
+    auto arg = args.get(0);
+    if (!arg) detail::error_handler().on_error("argument not found");
+    using iterator = typename ArgFormatter::iterator;
+    return visit_format_arg(
+        detail::default_arg_formatter<iterator, Char>{out, args, loc}, arg);
+  }
+  detail::format_handler<ArgFormatter, Char, Context> h(out, format_str, args,
+                                                        loc);
+  detail::parse_format_string<false>(format_str, h);
   return h.context.out();
 }
 
@@ -3228,44 +3319,42 @@ class bytes {
 template <> struct formatter<bytes> {
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    using handler_type = internal::dynamic_specs_handler<ParseContext>;
-    internal::specs_checker<handler_type> handler(handler_type(specs_, ctx),
-                                                  internal::type::string_type);
+    using handler_type = detail::dynamic_specs_handler<ParseContext>;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+                                                detail::type::string_type);
     auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
-    internal::check_string_type_spec(specs_.type, ctx.error_handler());
+    detail::check_string_type_spec(specs_.type, ctx.error_handler());
     return it;
   }
 
   template <typename FormatContext>
   auto format(bytes b, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::handle_dynamic_spec<internal::width_checker>(
-        specs_.width, specs_.width_ref, ctx);
-    internal::handle_dynamic_spec<internal::precision_checker>(
+    detail::handle_dynamic_spec<detail::width_checker>(specs_.width,
+                                                       specs_.width_ref, ctx);
+    detail::handle_dynamic_spec<detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
-    using range_type =
-        internal::output_range<typename FormatContext::iterator, char>;
-    internal::basic_writer<range_type> writer(range_type(ctx.out()));
-    writer.write_bytes(b.data_, specs_);
-    return writer.out();
+    return detail::write_bytes(ctx.out(), b.data_, specs_);
   }
 
  private:
-  internal::dynamic_format_specs<char> specs_;
+  detail::dynamic_format_specs<char> specs_;
 };
 
-template <typename It, typename Char> struct arg_join : internal::view {
+template <typename It, typename Sentinel, typename Char>
+struct arg_join : detail::view {
   It begin;
-  It end;
+  Sentinel end;
   basic_string_view<Char> sep;
 
-  arg_join(It b, It e, basic_string_view<Char> s) : begin(b), end(e), sep(s) {}
+  arg_join(It b, Sentinel e, basic_string_view<Char> s)
+      : begin(b), end(e), sep(s) {}
 };
 
-template <typename It, typename Char>
-struct formatter<arg_join<It, Char>, Char>
+template <typename It, typename Sentinel, typename Char>
+struct formatter<arg_join<It, Sentinel, Char>, Char>
     : formatter<typename std::iterator_traits<It>::value_type, Char> {
   template <typename FormatContext>
-  auto format(const arg_join<It, Char>& value, FormatContext& ctx)
+  auto format(const arg_join<It, Sentinel, Char>& value, FormatContext& ctx)
       -> decltype(ctx.out()) {
     using base = formatter<typename std::iterator_traits<It>::value_type, Char>;
     auto it = value.begin;
@@ -3286,13 +3375,13 @@ struct formatter<arg_join<It, Char>, Char>
   Returns an object that formats the iterator range `[begin, end)` with elements
   separated by `sep`.
  */
-template <typename It>
-arg_join<It, char> join(It begin, It end, string_view sep) {
+template <typename It, typename Sentinel>
+arg_join<It, Sentinel, char> join(It begin, Sentinel end, string_view sep) {
   return {begin, end, sep};
 }
 
-template <typename It>
-arg_join<It, wchar_t> join(It begin, It end, wstring_view sep) {
+template <typename It, typename Sentinel>
+arg_join<It, Sentinel, wchar_t> join(It begin, Sentinel end, wstring_view sep) {
   return {begin, end, sep};
 }
 
@@ -3313,14 +3402,15 @@ arg_join<It, wchar_t> join(It begin, It end, wstring_view sep) {
   \endrst
  */
 template <typename Range>
-arg_join<internal::iterator_t<const Range>, char> join(const Range& range,
-                                                       string_view sep) {
+arg_join<detail::iterator_t<const Range>, detail::sentinel_t<const Range>, char>
+join(const Range& range, string_view sep) {
   return join(std::begin(range), std::end(range), sep);
 }
 
 template <typename Range>
-arg_join<internal::iterator_t<const Range>, wchar_t> join(const Range& range,
-                                                          wstring_view sep) {
+arg_join<detail::iterator_t<const Range>, detail::sentinel_t<const Range>,
+         wchar_t>
+join(const Range& range, wstring_view sep) {
   return join(std::begin(range), std::end(range), sep);
 }
 
@@ -3335,8 +3425,21 @@ arg_join<internal::iterator_t<const Range>, wchar_t> join(const Range& range,
     std::string answer = fmt::to_string(42);
   \endrst
  */
-template <typename T> inline std::string to_string(const T& value) {
-  return format("{}", value);
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+inline std::string to_string(const T& value) {
+  std::string result;
+  detail::write<char>(std::back_inserter(result), value);
+  return result;
+}
+
+template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
+inline std::string to_string(T value) {
+  // The buffer should be large enough to store the number including the sign or
+  // "false" for bool.
+  constexpr int max_size = detail::digits10<T>() + 2;
+  char buffer[max_size > 5 ? max_size : 5];
+  char* begin = buffer;
+  return std::string(begin, detail::write<char>(begin, value));
 }
 
 /**
@@ -3346,36 +3449,65 @@ template <typename T> inline std::wstring to_wstring(const T& value) {
   return format(L"{}", value);
 }
 
-template <typename Char, std::size_t SIZE>
+template <typename Char, size_t SIZE>
 std::basic_string<Char> to_string(const basic_memory_buffer<Char, SIZE>& buf) {
-  return std::basic_string<Char>(buf.data(), buf.size());
+  auto size = buf.size();
+  detail::assume(size < std::basic_string<Char>().max_size());
+  return std::basic_string<Char>(buf.data(), size);
 }
 
 template <typename Char>
-typename buffer_context<Char>::iterator internal::vformat_to(
-    internal::buffer<Char>& buf, basic_string_view<Char> format_str,
+typename buffer_context<Char>::iterator detail::vformat_to(
+    detail::buffer<Char>& buf, basic_string_view<Char> format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  using range = buffer_range<Char>;
-  return vformat_to<arg_formatter<range>>(buf, to_string_view(format_str),
-                                          args);
+  using af = arg_formatter<typename buffer_context<Char>::iterator, Char>;
+  return vformat_to<af>(std::back_inserter(buf), to_string_view(format_str),
+                        args);
 }
 
+#ifndef FMT_HEADER_ONLY
+extern template format_context::iterator detail::vformat_to(
+    detail::buffer<char>&, string_view, basic_format_args<format_context>);
+namespace detail {
+extern template FMT_API std::string grouping_impl<char>(locale_ref loc);
+extern template FMT_API std::string grouping_impl<wchar_t>(locale_ref loc);
+extern template FMT_API char thousands_sep_impl<char>(locale_ref loc);
+extern template FMT_API wchar_t thousands_sep_impl<wchar_t>(locale_ref loc);
+extern template FMT_API char decimal_point_impl(locale_ref loc);
+extern template FMT_API wchar_t decimal_point_impl(locale_ref loc);
+extern template int format_float<double>(double value, int precision,
+                                         float_specs specs, buffer<char>& buf);
+extern template int format_float<long double>(long double value, int precision,
+                                              float_specs specs,
+                                              buffer<char>& buf);
+int snprintf_float(float value, int precision, float_specs specs,
+                   buffer<char>& buf) = delete;
+extern template int snprintf_float<double>(double value, int precision,
+                                           float_specs specs,
+                                           buffer<char>& buf);
+extern template int snprintf_float<long double>(long double value,
+                                                int precision,
+                                                float_specs specs,
+                                                buffer<char>& buf);
+}  // namespace detail
+#endif
+
 template <typename S, typename Char = char_t<S>,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
-inline typename buffer_context<Char>::iterator vformat_to(
-    internal::buffer<Char>& buf, const S& format_str,
-    basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  return internal::vformat_to(buf, to_string_view(format_str), args);
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
+inline typename FMT_BUFFER_CONTEXT(Char)::iterator vformat_to(
+    detail::buffer<Char>& buf, const S& format_str,
+    basic_format_args<FMT_BUFFER_CONTEXT(type_identity_t<Char>)> args) {
+  return detail::vformat_to(buf, to_string_view(format_str), args);
 }
 
-template <typename S, typename... Args, std::size_t SIZE = inline_buffer_size,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+template <typename S, typename... Args, size_t SIZE = inline_buffer_size,
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 inline typename buffer_context<Char>::iterator format_to(
     basic_memory_buffer<Char, SIZE>& buf, const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
+  detail::check_format_string<Args...>(format_str);
   using context = buffer_context<Char>;
-  return internal::vformat_to(buf, to_string_view(format_str),
-                              make_format_args<context>(args...));
+  return detail::vformat_to(buf, to_string_view(format_str),
+                            make_format_args<context>(args...));
 }
 
 template <typename OutputIt, typename Char = char>
@@ -3384,16 +3516,15 @@ using format_context_t = basic_format_context<OutputIt, Char>;
 template <typename OutputIt, typename Char = char>
 using format_args_t = basic_format_args<format_context_t<OutputIt, Char>>;
 
-template <typename S, typename OutputIt, typename... Args,
-          FMT_ENABLE_IF(
-              internal::is_output_iterator<OutputIt>::value &&
-              !internal::is_contiguous_back_insert_iterator<OutputIt>::value)>
+template <
+    typename S, typename OutputIt, typename... Args,
+    FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value &&
+                  !detail::is_contiguous_back_insert_iterator<OutputIt>::value)>
 inline OutputIt vformat_to(
     OutputIt out, const S& format_str,
     format_args_t<type_identity_t<OutputIt>, char_t<S>> args) {
-  using range = internal::output_range<OutputIt, char_t<S>>;
-  return vformat_to<arg_formatter<range>>(range(out),
-                                          to_string_view(format_str), args);
+  using af = detail::arg_formatter<OutputIt, char_t<S>>;
+  return vformat_to<af>(out, to_string_view(format_str), args);
 }
 
 /**
@@ -3409,11 +3540,11 @@ inline OutputIt vformat_to(
  */
 template <typename OutputIt, typename S, typename... Args,
           FMT_ENABLE_IF(
-              internal::is_output_iterator<OutputIt>::value &&
-              !internal::is_contiguous_back_insert_iterator<OutputIt>::value &&
-              internal::is_string<S>::value)>
+              detail::is_output_iterator<OutputIt>::value &&
+              !detail::is_contiguous_back_insert_iterator<OutputIt>::value &&
+              detail::is_string<S>::value)>
 inline OutputIt format_to(OutputIt out, const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
+  detail::check_format_string<Args...>(format_str);
   using context = format_context_t<OutputIt, char_t<S>>;
   return vformat_to(out, to_string_view(format_str),
                     make_format_args<context>(args...));
@@ -3423,12 +3554,12 @@ template <typename OutputIt> struct format_to_n_result {
   /** Iterator past the end of the output range. */
   OutputIt out;
   /** Total (not truncated) output size. */
-  std::size_t size;
+  size_t size;
 };
 
 template <typename OutputIt, typename Char = typename OutputIt::value_type>
 using format_to_n_context =
-    format_context_t<internal::truncating_iterator<OutputIt>, Char>;
+    format_context_t<detail::truncating_iterator<OutputIt>, Char>;
 
 template <typename OutputIt, typename Char = typename OutputIt::value_type>
 using format_to_n_args = basic_format_args<format_to_n_context<OutputIt, Char>>;
@@ -3441,11 +3572,11 @@ make_format_to_n_args(const Args&... args) {
 }
 
 template <typename OutputIt, typename Char, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value)>
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value)>
 inline format_to_n_result<OutputIt> vformat_to_n(
-    OutputIt out, std::size_t n, basic_string_view<Char> format_str,
+    OutputIt out, size_t n, basic_string_view<Char> format_str,
     format_to_n_args<type_identity_t<OutputIt>, type_identity_t<Char>> args) {
-  auto it = vformat_to(internal::truncating_iterator<OutputIt>(out, n),
+  auto it = vformat_to(detail::truncating_iterator<OutputIt>(out, n),
                        format_str, args);
   return {it.base(), it.count()};
 }
@@ -3458,23 +3589,23 @@ inline format_to_n_result<OutputIt> vformat_to_n(
  \endrst
  */
 template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value&&
-                            internal::is_output_iterator<OutputIt>::value)>
-inline format_to_n_result<OutputIt> format_to_n(OutputIt out, std::size_t n,
+          FMT_ENABLE_IF(detail::is_string<S>::value&&
+                            detail::is_output_iterator<OutputIt>::value)>
+inline format_to_n_result<OutputIt> format_to_n(OutputIt out, size_t n,
                                                 const S& format_str,
                                                 const Args&... args) {
-  internal::check_format_string<Args...>(format_str);
+  detail::check_format_string<Args...>(format_str);
   using context = format_to_n_context<OutputIt, char_t<S>>;
   return vformat_to_n(out, n, to_string_view(format_str),
                       make_format_args<context>(args...));
 }
 
-template <typename Char>
-inline std::basic_string<Char> internal::vformat(
+template <typename Char, enable_if_t<(!std::is_same<Char, char>::value), int>>
+std::basic_string<Char> detail::vformat(
     basic_string_view<Char> format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  internal::vformat_to(buffer, format_str, args);
+  detail::vformat_to(buffer, format_str, args);
   return to_string(buffer);
 }
 
@@ -3483,15 +3614,15 @@ inline std::basic_string<Char> internal::vformat(
   ``format(format_str, args...)``.
  */
 template <typename... Args>
-inline std::size_t formatted_size(string_view format_str, const Args&... args) {
-  return format_to(internal::counting_iterator(), format_str, args...).count();
+inline size_t formatted_size(string_view format_str, const Args&... args) {
+  return format_to(detail::counting_iterator(), format_str, args...).count();
 }
 
 template <typename Char, FMT_ENABLE_IF(std::is_same<Char, wchar_t>::value)>
 void vprint(std::FILE* f, basic_string_view<Char> format_str,
             wformat_args args) {
   wmemory_buffer buffer;
-  internal::vformat_to(buffer, format_str, args);
+  detail::vformat_to(buffer, format_str, args);
   buffer.push_back(L'\0');
   if (std::fputws(buffer.data(), f) == -1)
     FMT_THROW(system_error(errno, "cannot write to file"));
@@ -3503,18 +3634,15 @@ void vprint(basic_string_view<Char> format_str, wformat_args args) {
 }
 
 #if FMT_USE_USER_DEFINED_LITERALS
-namespace internal {
+namespace detail {
 
 #  if FMT_USE_UDL_TEMPLATE
 template <typename Char, Char... CHARS> class udl_formatter {
  public:
   template <typename... Args>
   std::basic_string<Char> operator()(Args&&... args) const {
-    FMT_CONSTEXPR_DECL Char s[] = {CHARS..., '\0'};
-    FMT_CONSTEXPR_DECL bool invalid_format =
-        do_check_format_string<Char, error_handler, remove_cvref_t<Args>...>(
-            basic_string_view<Char>(s, sizeof...(CHARS)));
-    (void)invalid_format;
+    static FMT_CONSTEXPR_DECL Char s[] = {CHARS..., '\0'};
+    check_format_string<remove_cvref_t<Args>...>(FMT_STRING(s));
     return format(s, std::forward<Args>(args)...);
   }
 };
@@ -3530,39 +3658,23 @@ template <typename Char> struct udl_formatter {
 #  endif  // FMT_USE_UDL_TEMPLATE
 
 template <typename Char> struct udl_arg {
-  basic_string_view<Char> str;
+  const Char* str;
 
-  template <typename T> named_arg<T, Char> operator=(T&& value) const {
+  template <typename T> named_arg<Char, T> operator=(T&& value) const {
     return {str, std::forward<T>(value)};
   }
 };
-
-// Converts string literals to basic_string_view.
-template <typename Char, size_t N>
-FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
-    const Char (&s)[N]) {
-  // Remove trailing null character if needed. Won't be present if this is used
-  // with raw character array (i.e. not defined as a string).
-  return {s,
-          N - ((std::char_traits<Char>::to_int_type(s[N - 1]) == 0) ? 1 : 0)};
-}
-
-// Converts string_view to basic_string_view.
-template <typename Char>
-FMT_CONSTEXPR basic_string_view<Char> compile_string_to_view(
-    const std_string_view<Char>& s) {
-  return {s.data(), s.size()};
-}
-}  // namespace internal
+}  // namespace detail
 
 inline namespace literals {
 #  if FMT_USE_UDL_TEMPLATE
 #    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wpedantic"
 #    if FMT_CLANG_VERSION
 #      pragma GCC diagnostic ignored "-Wgnu-string-literal-operator-template"
 #    endif
 template <typename Char, Char... CHARS>
-FMT_CONSTEXPR internal::udl_formatter<Char, CHARS...> operator""_format() {
+FMT_CONSTEXPR detail::udl_formatter<Char, CHARS...> operator""_format() {
   return {};
 }
 #    pragma GCC diagnostic pop
@@ -3577,12 +3689,12 @@ FMT_CONSTEXPR internal::udl_formatter<Char, CHARS...> operator""_format() {
     std::string message = "The answer is {}"_format(42);
   \endrst
  */
-FMT_CONSTEXPR internal::udl_formatter<char> operator"" _format(const char* s,
-                                                               std::size_t n) {
+FMT_CONSTEXPR detail::udl_formatter<char> operator"" _format(const char* s,
+                                                             size_t n) {
   return {{s, n}};
 }
-FMT_CONSTEXPR internal::udl_formatter<wchar_t> operator"" _format(
-    const wchar_t* s, std::size_t n) {
+FMT_CONSTEXPR detail::udl_formatter<wchar_t> operator"" _format(
+    const wchar_t* s, size_t n) {
   return {{s, n}};
 }
 #  endif  // FMT_USE_UDL_TEMPLATE
@@ -3597,47 +3709,16 @@ FMT_CONSTEXPR internal::udl_formatter<wchar_t> operator"" _format(
     fmt::print("Elapsed time: {s:.2f} seconds", "s"_a=1.23);
   \endrst
  */
-FMT_CONSTEXPR internal::udl_arg<char> operator"" _a(const char* s,
-                                                    std::size_t n) {
-  return {{s, n}};
+FMT_CONSTEXPR detail::udl_arg<char> operator"" _a(const char* s, size_t) {
+  return {s};
 }
-FMT_CONSTEXPR internal::udl_arg<wchar_t> operator"" _a(const wchar_t* s,
-                                                       std::size_t n) {
-  return {{s, n}};
+FMT_CONSTEXPR detail::udl_arg<wchar_t> operator"" _a(const wchar_t* s, size_t) {
+  return {s};
 }
 }  // namespace literals
 #endif  // FMT_USE_USER_DEFINED_LITERALS
 FMT_END_NAMESPACE
 
-#define FMT_STRING_IMPL(s, ...)                                     \
-  [] {                                                              \
-    /* Use a macro-like name to avoid shadowing warnings. */        \
-    struct FMT_COMPILE_STRING : fmt::compile_string {               \
-      using char_type = fmt::remove_cvref_t<decltype(s[0])>;        \
-      FMT_MAYBE_UNUSED __VA_ARGS__ FMT_CONSTEXPR                    \
-      operator fmt::basic_string_view<char_type>() const {          \
-        return fmt::internal::compile_string_to_view<char_type>(s); \
-      }                                                             \
-    };                                                              \
-    return FMT_COMPILE_STRING();                                    \
-  }()
-
-/**
-  \rst
-  Constructs a compile-time format string from a string literal *s*.
-
-  **Example**::
-
-    // A compile-time error because 'd' is an invalid specifier for strings.
-    std::string s = format(FMT_STRING("{:d}"), "foo");
-  \endrst
- */
-#define FMT_STRING(s) FMT_STRING_IMPL(s, )
-
-#if defined(FMT_STRING_ALIAS) && FMT_STRING_ALIAS
-#  define fmt(s) FMT_STRING_IMPL(s, [[deprecated]])
-#endif
-
 #ifdef FMT_HEADER_ONLY
 #  define FMT_FUNC inline
 #  include "format-inl.h"
diff --git a/include/fmt/locale.h b/include/fmt/locale.h
index 70bc1935..988d15cd 100644
--- a/include/fmt/locale.h
+++ b/include/fmt/locale.h
@@ -14,15 +14,15 @@
 
 FMT_BEGIN_NAMESPACE
 
-namespace internal {
+namespace detail {
 template <typename Char>
 typename buffer_context<Char>::iterator vformat_to(
     const std::locale& loc, buffer<Char>& buf,
     basic_string_view<Char> format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  using range = buffer_range<Char>;
-  return vformat_to<arg_formatter<range>>(buf, to_string_view(format_str), args,
-                                          internal::locale_ref(loc));
+  using af = arg_formatter<typename buffer_context<Char>::iterator, Char>;
+  return vformat_to<af>(std::back_inserter(buf), to_string_view(format_str),
+                        args, detail::locale_ref(loc));
 }
 
 template <typename Char>
@@ -30,43 +30,43 @@ std::basic_string<Char> vformat(
     const std::locale& loc, basic_string_view<Char> format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  internal::vformat_to(loc, buffer, format_str, args);
+  detail::vformat_to(loc, buffer, format_str, args);
   return fmt::to_string(buffer);
 }
-}  // namespace internal
+}  // namespace detail
 
 template <typename S, typename Char = char_t<S>>
 inline std::basic_string<Char> vformat(
     const std::locale& loc, const S& format_str,
     basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  return internal::vformat(loc, to_string_view(format_str), args);
+  return detail::vformat(loc, to_string_view(format_str), args);
 }
 
 template <typename S, typename... Args, typename Char = char_t<S>>
 inline std::basic_string<Char> format(const std::locale& loc,
                                       const S& format_str, Args&&... args) {
-  return internal::vformat(
+  return detail::vformat(
       loc, to_string_view(format_str),
-      internal::make_args_checked<Args...>(format_str, args...));
+      detail::make_args_checked<Args...>(format_str, args...));
 }
 
 template <typename S, typename OutputIt, typename... Args,
           typename Char = enable_if_t<
-              internal::is_output_iterator<OutputIt>::value, char_t<S>>>
+              detail::is_output_iterator<OutputIt>::value, char_t<S>>>
 inline OutputIt vformat_to(
     OutputIt out, const std::locale& loc, const S& format_str,
     format_args_t<type_identity_t<OutputIt>, Char> args) {
-  using range = internal::output_range<OutputIt, Char>;
-  return vformat_to<arg_formatter<range>>(
-      range(out), to_string_view(format_str), args, internal::locale_ref(loc));
+  using af = detail::arg_formatter<OutputIt, Char>;
+  return vformat_to<af>(out, to_string_view(format_str), args,
+                        detail::locale_ref(loc));
 }
 
 template <typename OutputIt, typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_output_iterator<OutputIt>::value&&
-                            internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_output_iterator<OutputIt>::value&&
+                            detail::is_string<S>::value)>
 inline OutputIt format_to(OutputIt out, const std::locale& loc,
                           const S& format_str, Args&&... args) {
-  internal::check_format_string<Args...>(format_str);
+  detail::check_format_string<Args...>(format_str);
   using context = format_context_t<OutputIt, char_t<S>>;
   format_arg_store<context, Args...> as{args...};
   return vformat_to(out, loc, to_string_view(format_str),
diff --git a/include/fmt/os.h b/include/fmt/os.h
index a1a0d03b..a9517ef8 100644
--- a/include/fmt/os.h
+++ b/include/fmt/os.h
@@ -50,7 +50,7 @@
 #ifdef FMT_SYSTEM
 #  define FMT_POSIX_CALL(call) FMT_SYSTEM(call)
 #else
-#  define FMT_SYSTEM(call) call
+#  define FMT_SYSTEM(call) ::call
 #  ifdef _WIN32
 // Fix warnings about deprecated symbols.
 #    define FMT_POSIX_CALL(call) ::_##call
@@ -133,7 +133,7 @@ class error_code {
 };
 
 #ifdef _WIN32
-namespace internal {
+namespace detail {
 // A converter from UTF-16 to UTF-8.
 // It is only provided for Windows since other systems support UTF-8 natively.
 class utf16_to_utf8 {
@@ -156,7 +156,7 @@ class utf16_to_utf8 {
 
 FMT_API void format_windows_error(buffer<char>& out, int error_code,
                                   string_view message) FMT_NOEXCEPT;
-}  // namespace internal
+}  // namespace detail
 
 /** A Windows error. */
 class windows_error : public system_error {
@@ -277,7 +277,8 @@ class file {
   enum {
     RDONLY = FMT_POSIX(O_RDONLY),  // Open for reading only.
     WRONLY = FMT_POSIX(O_WRONLY),  // Open for writing only.
-    RDWR = FMT_POSIX(O_RDWR)       // Open for reading and writing.
+    RDWR = FMT_POSIX(O_RDWR),      // Open for reading and writing.
+    CREATE = FMT_POSIX(O_CREAT)    // Create if the file doesn't exist.
   };
 
   // Constructs a file object which doesn't represent any file.
@@ -313,10 +314,10 @@ class file {
   FMT_API long long size() const;
 
   // Attempts to read count bytes from the file into the specified buffer.
-  FMT_API std::size_t read(void* buffer, std::size_t count);
+  FMT_API size_t read(void* buffer, size_t count);
 
   // Attempts to write count bytes from the specified buffer to the file.
-  FMT_API std::size_t write(const void* buffer, std::size_t count);
+  FMT_API size_t write(const void* buffer, size_t count);
 
   // Duplicates a file descriptor with the dup function and returns
   // the duplicate as a file object.
@@ -341,6 +342,63 @@ class file {
 
 // Returns the memory page size.
 long getpagesize();
+
+class direct_buffered_file;
+
+template <typename S, typename... Args>
+void print(direct_buffered_file& f, const S& format_str,
+           const Args&... args);
+
+// A buffered file with a direct buffer access and no synchronization.
+class direct_buffered_file {
+ private:
+  file file_;
+
+  enum { buffer_size = 4096 };
+  char buffer_[buffer_size];
+  int pos_;
+
+  void flush() {
+    if (pos_ == 0) return;
+    file_.write(buffer_, pos_);
+    pos_ = 0;
+  }
+
+  int free_capacity() const { return buffer_size - pos_; }
+
+ public:
+  direct_buffered_file(cstring_view path, int oflag)
+    : file_(path, oflag), pos_(0) {}
+
+  ~direct_buffered_file() {
+    flush();
+  }
+
+  void close() {
+    flush();
+    file_.close();
+  }
+
+  template <typename S, typename... Args>
+  friend void print(direct_buffered_file& f, const S& format_str,
+                    const Args&... args) {
+    // We could avoid double buffering.
+    auto buf = fmt::memory_buffer();
+    fmt::format_to(std::back_inserter(buf), format_str, args...);
+    auto remaining_pos = 0;
+    auto remaining_size = buf.size();
+    while (remaining_size > detail::to_unsigned(f.free_capacity())) {
+      auto size = f.free_capacity();
+      memcpy(f.buffer_ + f.pos_, buf.data() + remaining_pos, size);
+      f.pos_ += size;
+      f.flush();
+      remaining_pos += size;
+      remaining_size -= size;
+    }
+    memcpy(f.buffer_ + f.pos_, buf.data() + remaining_pos, remaining_size);
+    f.pos_ += static_cast<int>(remaining_size);
+  }
+};
 #endif  // FMT_USE_FCNTL
 
 #ifdef FMT_LOCALE
diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index c4831533..c16107f7 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -9,10 +9,15 @@
 #define FMT_OSTREAM_H_
 
 #include <ostream>
+
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+
+template <typename Char> class basic_printf_parse_context;
+template <typename OutputIt, typename Char> class basic_printf_context;
+
+namespace detail {
 
 template <class Char> class formatbuf : public std::basic_streambuf<Char> {
  private:
@@ -75,7 +80,7 @@ template <typename T, typename Char> class is_streamable {
 
 // Write the content of buf to os.
 template <typename Char>
-void write(std::basic_ostream<Char>& os, buffer<Char>& buf) {
+void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
   const Char* buf_data = buf.data();
   using unsigned_streamsize = std::make_unsigned<std::streamsize>::type;
   unsigned_streamsize size = buf.size();
@@ -93,34 +98,53 @@ void format_value(buffer<Char>& buf, const T& value,
                   locale_ref loc = locale_ref()) {
   formatbuf<Char> format_buf(buf);
   std::basic_ostream<Char> output(&format_buf);
-  #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
+#if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
   if (loc) output.imbue(loc.get<std::locale>());
-  #endif
-  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
+#endif
   output << value;
+  output.exceptions(std::ios_base::failbit | std::ios_base::badbit);
   buf.resize(buf.size());
 }
 
 // Formats an object of type T that has an overloaded ostream operator<<.
 template <typename T, typename Char>
 struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
-    : formatter<basic_string_view<Char>, Char> {
-  template <typename Context>
-  auto format(const T& value, Context& ctx) -> decltype(ctx.out()) {
+    : private formatter<basic_string_view<Char>, Char> {
+  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
+      -> decltype(ctx.begin()) {
+    return formatter<basic_string_view<Char>, Char>::parse(ctx);
+  }
+  template <typename ParseCtx,
+            FMT_ENABLE_IF(std::is_same<
+                          ParseCtx, basic_printf_parse_context<Char>>::value)>
+  auto parse(ParseCtx& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename OutputIt>
+  auto format(const T& value, basic_format_context<OutputIt, Char>& ctx)
+      -> OutputIt {
     basic_memory_buffer<Char> buffer;
     format_value(buffer, value, ctx.locale());
     basic_string_view<Char> str(buffer.data(), buffer.size());
     return formatter<basic_string_view<Char>, Char>::format(str, ctx);
   }
+  template <typename OutputIt>
+  auto format(const T& value, basic_printf_context<OutputIt, Char>& ctx)
+      -> OutputIt {
+    basic_memory_buffer<Char> buffer;
+    format_value(buffer, value, ctx.locale());
+    return std::copy(buffer.begin(), buffer.end(), ctx.out());
+  }
 };
-}  // namespace internal
+}  // namespace detail
 
 template <typename Char>
 void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
             basic_format_args<buffer_context<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  internal::vformat_to(buffer, format_str, args);
-  internal::write(os, buffer);
+  detail::vformat_to(buffer, format_str, args);
+  detail::write_buffer(os, buffer);
 }
 
 /**
@@ -133,10 +157,10 @@ void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
   \endrst
  */
 template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 void print(std::basic_ostream<Char>& os, const S& format_str, Args&&... args) {
   vprint(os, to_string_view(format_str),
-         internal::make_args_checked<Args...>(format_str, args...));
+         detail::make_args_checked<Args...>(format_str, args...));
 }
 FMT_END_NAMESPACE
 
diff --git a/include/fmt/posix.h b/include/fmt/posix.h
index 0e7bc646..da19e9d5 100644
--- a/include/fmt/posix.h
+++ b/include/fmt/posix.h
@@ -1,2 +1,2 @@
 #include "os.h"
-#warning "fmt/posix.h is deprecated; use fmt/os.h instead"
\ No newline at end of file
+#warning "fmt/posix.h is deprecated; use fmt/os.h instead"
diff --git a/include/fmt/printf.h b/include/fmt/printf.h
index a7902280..d4440ed1 100644
--- a/include/fmt/printf.h
+++ b/include/fmt/printf.h
@@ -14,7 +14,7 @@
 #include "ostream.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
 // Checks if a value fits in int - used to avoid warnings about comparing
 // signed and unsigned integers.
@@ -90,11 +90,11 @@ template <typename T, typename Context> class arg_converter {
     if (const_check(sizeof(target_type) <= sizeof(int))) {
       // Extra casts are used to silence warnings.
       if (is_signed) {
-        arg_ = internal::make_arg<Context>(
+        arg_ = detail::make_arg<Context>(
             static_cast<int>(static_cast<target_type>(value)));
       } else {
         using unsigned_type = typename make_unsigned_or_bool<target_type>::type;
-        arg_ = internal::make_arg<Context>(
+        arg_ = detail::make_arg<Context>(
             static_cast<unsigned>(static_cast<unsigned_type>(value)));
       }
     } else {
@@ -102,9 +102,9 @@ template <typename T, typename Context> class arg_converter {
         // glibc's printf doesn't sign extend arguments of smaller types:
         //   std::printf("%lld", -42);  // prints "4294967254"
         // but we don't have to do the same because it's a UB.
-        arg_ = internal::make_arg<Context>(static_cast<long long>(value));
+        arg_ = detail::make_arg<Context>(static_cast<long long>(value));
       } else {
-        arg_ = internal::make_arg<Context>(
+        arg_ = detail::make_arg<Context>(
             static_cast<typename make_unsigned_or_bool<U>::type>(value));
       }
     }
@@ -133,7 +133,7 @@ template <typename Context> class char_converter {
 
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
   void operator()(T value) {
-    arg_ = internal::make_arg<Context>(
+    arg_ = detail::make_arg<Context>(
         static_cast<typename Context::char_type>(value));
   }
 
@@ -141,6 +141,13 @@ template <typename Context> class char_converter {
   void operator()(T) {}  // No conversion needed for non-integral types.
 };
 
+// An argument visitor that return a pointer to a C string if argument is a
+// string or null otherwise.
+template <typename Char> struct get_cstring {
+  template <typename T> const Char* operator()(T) { return nullptr; }
+  const Char* operator()(const Char* s) { return s; }
+};
+
 // Checks if an argument is a valid printf width specifier and sets
 // left alignment if it is negative.
 template <typename Char> class printf_width_handler {
@@ -155,7 +162,7 @@ template <typename Char> class printf_width_handler {
   template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
   unsigned operator()(T value) {
     auto width = static_cast<uint32_or_64_or_128_t<T>>(value);
-    if (internal::is_negative(value)) {
+    if (detail::is_negative(value)) {
       specs_.align = align::left;
       width = 0 - width;
     }
@@ -172,23 +179,25 @@ template <typename Char> class printf_width_handler {
 };
 
 template <typename Char, typename Context>
-void printf(buffer<Char>& buf, basic_string_view<Char> format,
-            basic_format_args<Context> args) {
+void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
+             basic_format_args<Context> args) {
   Context(std::back_inserter(buf), format, args).format();
 }
+}  // namespace detail
 
-template <typename OutputIt, typename Char, typename Context>
-internal::truncating_iterator<OutputIt> printf(
-    internal::truncating_iterator<OutputIt> it, basic_string_view<Char> format,
-    basic_format_args<Context> args) {
-  return Context(it, format, args).format();
+// For printing into memory_buffer.
+template <typename Char, typename Context>
+FMT_DEPRECATED void printf(detail::buffer<Char>& buf,
+                           basic_string_view<Char> format,
+                           basic_format_args<Context> args) {
+  return detail::vprintf(buf, format, args);
 }
-}  // namespace internal
-
-using internal::printf;  // For printing into memory_buffer.
-
-template <typename Range> class printf_arg_formatter;
+using detail::vprintf;
 
+template <typename Char>
+class basic_printf_parse_context : public basic_format_parse_context<Char> {
+  using basic_format_parse_context<Char>::basic_format_parse_context;
+};
 template <typename OutputIt, typename Char> class basic_printf_context;
 
 /**
@@ -196,15 +205,15 @@ template <typename OutputIt, typename Char> class basic_printf_context;
   The ``printf`` argument formatter.
   \endrst
  */
-template <typename Range>
-class printf_arg_formatter : public internal::arg_formatter_base<Range> {
+template <typename OutputIt, typename Char>
+class printf_arg_formatter : public detail::arg_formatter_base<OutputIt, Char> {
  public:
-  using iterator = typename Range::iterator;
+  using iterator = OutputIt;
 
  private:
-  using char_type = typename Range::value_type;
-  using base = internal::arg_formatter_base<Range>;
-  using context_type = basic_printf_context<iterator, char_type>;
+  using char_type = Char;
+  using base = detail::arg_formatter_base<OutputIt, Char>;
+  using context_type = basic_printf_context<OutputIt, Char>;
 
   context_type& context_;
 
@@ -229,9 +238,9 @@ class printf_arg_formatter : public internal::arg_formatter_base<Range> {
     \endrst
    */
   printf_arg_formatter(iterator iter, format_specs& specs, context_type& ctx)
-      : base(Range(iter), &specs, internal::locale_ref()), context_(ctx) {}
+      : base(iter, &specs, detail::locale_ref()), context_(ctx) {}
 
-  template <typename T, FMT_ENABLE_IF(fmt::internal::is_integral<T>::value)>
+  template <typename T, FMT_ENABLE_IF(fmt::detail::is_integral<T>::value)>
   iterator operator()(T value) {
     // MSVC2013 fails to compile separate overloads for bool and char_type so
     // use std::is_same instead.
@@ -246,7 +255,11 @@ class printf_arg_formatter : public internal::arg_formatter_base<Range> {
         return (*this)(static_cast<int>(value));
       fmt_specs.sign = sign::none;
       fmt_specs.alt = false;
-      fmt_specs.align = align::right;
+      fmt_specs.fill[0] = ' ';  // Ignore '0' flag for char types.
+      // align::numeric needs to be overwritten here since the '0' flag is
+      // ignored for non-numeric types
+      if (fmt_specs.align == align::none || fmt_specs.align == align::numeric)
+        fmt_specs.align = align::right;
       return base::operator()(value);
     } else {
       return base::operator()(value);
@@ -312,18 +325,21 @@ template <typename T> struct printf_formatter {
 
   template <typename FormatContext>
   auto format(const T& value, FormatContext& ctx) -> decltype(ctx.out()) {
-    internal::format_value(internal::get_container(ctx.out()), value);
+    detail::format_value(detail::get_container(ctx.out()), value);
     return ctx.out();
   }
 };
 
-/** This template formats data and writes the output to a writer. */
+/**
+ This template formats data and writes the output through an output iterator.
+ */
 template <typename OutputIt, typename Char> class basic_printf_context {
  public:
   /** The character type for the output. */
   using char_type = Char;
   using iterator = OutputIt;
   using format_arg = basic_format_arg<basic_printf_context>;
+  using parse_context_type = basic_printf_parse_context<Char>;
   template <typename T> using formatter_type = printf_formatter<T>;
 
  private:
@@ -331,7 +347,7 @@ template <typename OutputIt, typename Char> class basic_printf_context {
 
   OutputIt out_;
   basic_format_args<basic_printf_context> args_;
-  basic_format_parse_context<Char> parse_ctx_;
+  parse_context_type parse_ctx_;
 
   static void parse_flags(format_specs& specs, const Char*& it,
                           const Char* end);
@@ -346,9 +362,8 @@ template <typename OutputIt, typename Char> class basic_printf_context {
  public:
   /**
    \rst
-   Constructs a ``printf_context`` object. References to the arguments and
-   the writer are stored in the context object so make sure they have
-   appropriate lifetimes.
+   Constructs a ``printf_context`` object. References to the arguments are
+   stored in the context object so make sure they have appropriate lifetimes.
    \endrst
    */
   basic_printf_context(OutputIt out, basic_string_view<char_type> format_str,
@@ -358,18 +373,18 @@ template <typename OutputIt, typename Char> class basic_printf_context {
   OutputIt out() { return out_; }
   void advance_to(OutputIt it) { out_ = it; }
 
-  internal::locale_ref locale() { return {}; }
+  detail::locale_ref locale() { return {}; }
 
   format_arg arg(int id) const { return args_.get(id); }
 
-  basic_format_parse_context<Char>& parse_context() { return parse_ctx_; }
+  parse_context_type& parse_context() { return parse_ctx_; }
 
   FMT_CONSTEXPR void on_error(const char* message) {
     parse_ctx_.on_error(message);
   }
 
   /** Formats stored arguments and writes the output to the range. */
-  template <typename ArgFormatter = printf_arg_formatter<buffer_range<Char>>>
+  template <typename ArgFormatter = printf_arg_formatter<OutputIt, Char>>
   OutputIt format();
 };
 
@@ -389,7 +404,9 @@ void basic_printf_context<OutputIt, Char>::parse_flags(format_specs& specs,
       specs.fill[0] = '0';
       break;
     case ' ':
-      specs.sign = sign::space;
+      if (specs.sign != sign::plus) {
+        specs.sign = sign::space;
+      }
       break;
     case '#':
       specs.alt = true;
@@ -407,7 +424,7 @@ basic_printf_context<OutputIt, Char>::get_arg(int arg_index) {
     arg_index = parse_ctx_.next_arg_id();
   else
     parse_ctx_.check_arg_id(--arg_index);
-  return internal::get_arg(*this, arg_index);
+  return detail::get_arg(*this, arg_index);
 }
 
 template <typename OutputIt, typename Char>
@@ -419,7 +436,7 @@ int basic_printf_context<OutputIt, Char>::parse_header(const Char*& it,
   if (c >= '0' && c <= '9') {
     // Parse an argument index (if followed by '$') or a width possibly
     // preceded with '0' flag(s).
-    internal::error_handler eh;
+    detail::error_handler eh;
     int value = parse_nonnegative_int(it, end, eh);
     if (it != end && *it == '$') {  // value is an argument index
       ++it;
@@ -438,12 +455,12 @@ int basic_printf_context<OutputIt, Char>::parse_header(const Char*& it,
   // Parse width.
   if (it != end) {
     if (*it >= '0' && *it <= '9') {
-      internal::error_handler eh;
+      detail::error_handler eh;
       specs.width = parse_nonnegative_int(it, end, eh);
     } else if (*it == '*') {
       ++it;
       specs.width = static_cast<int>(visit_format_arg(
-          internal::printf_width_handler<char_type>(specs), get_arg()));
+          detail::printf_width_handler<char_type>(specs), get_arg()));
     }
   }
   return arg_index;
@@ -471,38 +488,52 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
 
     // Parse argument index, flags and width.
     int arg_index = parse_header(it, end, specs);
-    if (arg_index == 0) on_error("argument index out of range");
+    if (arg_index == 0) on_error("argument not found");
 
     // Parse precision.
     if (it != end && *it == '.') {
       ++it;
       c = it != end ? *it : 0;
       if ('0' <= c && c <= '9') {
-        internal::error_handler eh;
+        detail::error_handler eh;
         specs.precision = parse_nonnegative_int(it, end, eh);
       } else if (c == '*') {
         ++it;
         specs.precision = static_cast<int>(
-            visit_format_arg(internal::printf_precision_handler(), get_arg()));
+            visit_format_arg(detail::printf_precision_handler(), get_arg()));
       } else {
         specs.precision = 0;
       }
     }
 
     format_arg arg = get_arg(arg_index);
-    if (specs.alt && visit_format_arg(internal::is_zero_int(), arg))
+    // For d, i, o, u, x, and X conversion specifiers, if a precision is
+    // specified, the '0' flag is ignored
+    if (specs.precision >= 0 && arg.is_integral())
+      specs.fill[0] =
+          ' ';  // Ignore '0' flag for non-numeric types or if '-' present.
+    if (specs.precision >= 0 && arg.type() == detail::type::cstring_type) {
+      auto str = visit_format_arg(detail::get_cstring<Char>(), arg);
+      auto str_end = str + specs.precision;
+      auto nul = std::find(str, str_end, Char());
+      arg = detail::make_arg<basic_printf_context>(basic_string_view<Char>(
+          str,
+          detail::to_unsigned(nul != str_end ? nul - str : specs.precision)));
+    }
+    if (specs.alt && visit_format_arg(detail::is_zero_int(), arg))
       specs.alt = false;
     if (specs.fill[0] == '0') {
-      if (arg.is_arithmetic())
+      if (arg.is_arithmetic() && specs.align != align::left)
         specs.align = align::numeric;
       else
-        specs.fill[0] = ' ';  // Ignore '0' flag for non-numeric types.
+        specs.fill[0] = ' ';  // Ignore '0' flag for non-numeric types or if '-'
+                              // flag is also present.
     }
 
     // Parse length and convert the argument to the required type.
     c = it != end ? *it++ : 0;
     char_type t = it != end ? *it : 0;
-    using internal::convert_arg;
+    using detail::convert_arg;
     switch (c) {
     case 'h':
       if (t == 'h') {
@@ -526,7 +557,7 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
       convert_arg<intmax_t>(arg, t);
       break;
     case 'z':
-      convert_arg<std::size_t>(arg, t);
+      convert_arg<size_t>(arg, t);
       break;
     case 't':
       convert_arg<std::ptrdiff_t>(arg, t);
@@ -551,7 +582,7 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
         specs.type = 'd';
         break;
       case 'c':
-        visit_format_arg(internal::char_converter<basic_printf_context>(arg),
+        visit_format_arg(detail::char_converter<basic_printf_context>(arg),
                          arg);
         break;
       }
@@ -560,15 +591,14 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
     start = it;
 
     // Format argument.
-    visit_format_arg(ArgFormatter(out, specs, *this), arg);
+    out = visit_format_arg(ArgFormatter(out, specs, *this), arg);
   }
   return std::copy(start, it, out);
 }
 
 template <typename Char>
 using basic_printf_context_t =
-    basic_printf_context<std::back_insert_iterator<internal::buffer<Char>>,
-                         Char>;
+    basic_printf_context<std::back_insert_iterator<detail::buffer<Char>>, Char>;
 
 using printf_context = basic_printf_context_t<char>;
 using wprintf_context = basic_printf_context_t<wchar_t>;
@@ -605,7 +635,7 @@ inline std::basic_string<Char> vsprintf(
     const S& format,
     basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
+  vprintf(buffer, to_string_view(format), args);
   return to_string(buffer);
 }
 
@@ -619,7 +649,7 @@ inline std::basic_string<Char> vsprintf(
   \endrst
 */
 template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 inline std::basic_string<Char> sprintf(const S& format, const Args&... args) {
   using context = basic_printf_context_t<Char>;
   return vsprintf(to_string_view(format), make_format_args<context>(args...));
@@ -630,8 +660,8 @@ inline int vfprintf(
     std::FILE* f, const S& format,
     basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
-  std::size_t size = buffer.size();
+  vprintf(buffer, to_string_view(format), args);
+  size_t size = buffer.size();
   return std::fwrite(buffer.data(), sizeof(Char), size, f) < size
              ? -1
              : static_cast<int>(size);
@@ -647,7 +677,7 @@ inline int vfprintf(
   \endrst
  */
 template <typename S, typename... Args,
-          typename Char = enable_if_t<internal::is_string<S>::value, char_t<S>>>
+          typename Char = enable_if_t<detail::is_string<S>::value, char_t<S>>>
 inline int fprintf(std::FILE* f, const S& format, const Args&... args) {
   using context = basic_printf_context_t<Char>;
   return vfprintf(f, to_string_view(format),
@@ -671,7 +701,7 @@ inline int vprintf(
   \endrst
  */
 template <typename S, typename... Args,
-          FMT_ENABLE_IF(internal::is_string<S>::value)>
+          FMT_ENABLE_IF(detail::is_string<S>::value)>
 inline int printf(const S& format_str, const Args&... args) {
   using context = basic_printf_context_t<char_t<S>>;
   return vprintf(to_string_view(format_str),
@@ -683,8 +713,8 @@ inline int vfprintf(
     std::basic_ostream<Char>& os, const S& format,
     basic_format_args<basic_printf_context_t<type_identity_t<Char>>> args) {
   basic_memory_buffer<Char> buffer;
-  printf(buffer, to_string_view(format), args);
-  internal::write(os, buffer);
+  vprintf(buffer, to_string_view(format), args);
+  detail::write_buffer(os, buffer);
   return static_cast<int>(buffer.size());
 }
 
@@ -693,7 +723,7 @@ template <typename ArgFormatter, typename Char,
           typename Context =
               basic_printf_context<typename ArgFormatter::iterator, Char>>
 typename ArgFormatter::iterator vprintf(
-    internal::buffer<Char>& out, basic_string_view<Char> format_str,
+    detail::buffer<Char>& out, basic_string_view<Char> format_str,
     basic_format_args<type_identity_t<Context>> args) {
   typename ArgFormatter::iterator iter(out);
   Context(iter, format_str, args).template format<ArgFormatter>();
diff --git a/include/fmt/ranges.h b/include/fmt/ranges.h
index f8f9adb7..c48f1727 100644
--- a/include/fmt/ranges.h
+++ b/include/fmt/ranges.h
@@ -33,7 +33,7 @@ template <typename Char> struct formatting_base {
 
 template <typename Char, typename Enable = void>
 struct formatting_range : formatting_base<Char> {
-  static FMT_CONSTEXPR_DECL const std::size_t range_length_limit =
+  static FMT_CONSTEXPR_DECL const size_t range_length_limit =
       FMT_RANGE_OUTPUT_LENGTH_LIMIT;  // output only up to N items from the
                                       // range.
   Char prefix;
@@ -54,7 +54,7 @@ struct formatting_tuple : formatting_base<Char> {
   static FMT_CONSTEXPR_DECL const bool add_prepostfix_space = false;
 };
 
-namespace internal {
+namespace detail {
 
 template <typename RangeT, typename OutputIterator>
 OutputIterator copy(const RangeT& range, OutputIterator out) {
@@ -118,26 +118,24 @@ template <typename T> class is_tuple_like_ {
 #if defined(__cpp_lib_integer_sequence) || FMT_MSC_VER >= 1900
 template <typename T, T... N>
 using integer_sequence = std::integer_sequence<T, N...>;
-template <std::size_t... N> using index_sequence = std::index_sequence<N...>;
-template <std::size_t N>
-using make_index_sequence = std::make_index_sequence<N>;
+template <size_t... N> using index_sequence = std::index_sequence<N...>;
+template <size_t N> using make_index_sequence = std::make_index_sequence<N>;
 #else
 template <typename T, T... N> struct integer_sequence {
   using value_type = T;
 
-  static FMT_CONSTEXPR std::size_t size() { return sizeof...(N); }
+  static FMT_CONSTEXPR size_t size() { return sizeof...(N); }
 };
 
-template <std::size_t... N>
-using index_sequence = integer_sequence<std::size_t, N...>;
+template <size_t... N> using index_sequence = integer_sequence<size_t, N...>;
 
-template <typename T, std::size_t N, T... Ns>
+template <typename T, size_t N, T... Ns>
 struct make_integer_sequence : make_integer_sequence<T, N - 1, N - 1, Ns...> {};
 template <typename T, T... Ns>
 struct make_integer_sequence<T, 0, Ns...> : integer_sequence<T, Ns...> {};
 
-template <std::size_t N>
-using make_index_sequence = make_integer_sequence<std::size_t, N>;
+template <size_t N>
+using make_index_sequence = make_integer_sequence<size_t, N>;
 #endif
 
 template <class Tuple, class F, size_t... Is>
@@ -185,11 +183,11 @@ FMT_CONSTEXPR const wchar_t* format_str_quoted(bool add_space, const wchar_t) {
   return add_space ? L" '{}'" : L"'{}'";
 }
 
-}  // namespace internal
+}  // namespace detail
 
 template <typename T> struct is_tuple_like {
   static FMT_CONSTEXPR_DECL const bool value =
-      internal::is_tuple_like_<T>::value && !internal::is_range_<T>::value;
+      detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
 };
 
 template <typename TupleT, typename Char>
@@ -202,17 +200,17 @@ struct formatter<TupleT, Char, enable_if_t<fmt::is_tuple_like<TupleT>::value>> {
         if (formatting.add_prepostfix_space) {
           *out++ = ' ';
         }
-        out = internal::copy(formatting.delimiter, out);
+        out = detail::copy(formatting.delimiter, out);
       }
       out = format_to(out,
-                      internal::format_str_quoted(
+                      detail::format_str_quoted(
                           (formatting.add_delimiter_spaces && i > 0), v),
                       v);
       ++i;
     }
 
     formatting_tuple<Char>& formatting;
-    std::size_t& i;
+    size_t& i;
     typename std::add_lvalue_reference<decltype(
         std::declval<FormatContext>().out())>::type out;
   };
@@ -228,14 +226,14 @@ struct formatter<TupleT, Char, enable_if_t<fmt::is_tuple_like<TupleT>::value>> {
   template <typename FormatContext = format_context>
   auto format(const TupleT& values, FormatContext& ctx) -> decltype(ctx.out()) {
     auto out = ctx.out();
-    std::size_t i = 0;
-    internal::copy(formatting.prefix, out);
+    size_t i = 0;
+    detail::copy(formatting.prefix, out);
 
-    internal::for_each(values, format_each<FormatContext>{formatting, i, out});
+    detail::for_each(values, format_each<FormatContext>{formatting, i, out});
     if (formatting.add_prepostfix_space) {
       *out++ = ' ';
     }
-    internal::copy(formatting.postfix, out);
+    detail::copy(formatting.postfix, out);
 
     return ctx.out();
   }
@@ -243,10 +241,9 @@ struct formatter<TupleT, Char, enable_if_t<fmt::is_tuple_like<TupleT>::value>> {
 
 template <typename T, typename Char> struct is_range {
   static FMT_CONSTEXPR_DECL const bool value =
-      internal::is_range_<T>::value &&
-      !internal::is_like_std_string<T>::value &&
+      detail::is_range_<T>::value && !detail::is_like_std_string<T>::value &&
       !std::is_convertible<T, std::basic_string<Char>>::value &&
-      !std::is_constructible<internal::std_string_view<Char>, T>::value;
+      !std::is_constructible<detail::std_string_view<Char>, T>::value;
 };
 
 template <typename RangeT, typename Char>
@@ -262,15 +259,17 @@ struct formatter<RangeT, Char,
   template <typename FormatContext>
   typename FormatContext::iterator format(const RangeT& values,
                                           FormatContext& ctx) {
-    auto out = internal::copy(formatting.prefix, ctx.out());
-    std::size_t i = 0;
-    for (auto it = values.begin(), end = values.end(); it != end; ++it) {
+    auto out = detail::copy(formatting.prefix, ctx.out());
+    size_t i = 0;
+    auto it = values.begin();
+    auto end = values.end();
+    for (; it != end; ++it) {
       if (i > 0) {
         if (formatting.add_prepostfix_space) *out++ = ' ';
-        out = internal::copy(formatting.delimiter, out);
+        out = detail::copy(formatting.delimiter, out);
       }
       out = format_to(out,
-                      internal::format_str_quoted(
+                      detail::format_str_quoted(
                           (formatting.add_delimiter_spaces && i > 0), *it),
                       *it);
       if (++i > formatting.range_length_limit) {
@@ -279,11 +278,11 @@ struct formatter<RangeT, Char,
       }
     }
     if (formatting.add_prepostfix_space) *out++ = ' ';
-    return internal::copy(formatting.postfix, out);
+    return detail::copy(formatting.postfix, out);
   }
 };
 
-template <typename Char, typename... T> struct tuple_arg_join : internal::view {
+template <typename Char, typename... T> struct tuple_arg_join : detail::view {
   const std::tuple<T...>& tuple;
   basic_string_view<Char> sep;
 
@@ -301,14 +300,14 @@ struct formatter<tuple_arg_join<Char, T...>, Char> {
   template <typename FormatContext>
   typename FormatContext::iterator format(
       const tuple_arg_join<Char, T...>& value, FormatContext& ctx) {
-    return format(value, ctx, internal::make_index_sequence<sizeof...(T)>{});
+    return format(value, ctx, detail::make_index_sequence<sizeof...(T)>{});
   }
 
  private:
   template <typename FormatContext, size_t... N>
   typename FormatContext::iterator format(
       const tuple_arg_join<Char, T...>& value, FormatContext& ctx,
-      internal::index_sequence<N...>) {
+      detail::index_sequence<N...>) {
     return format_args(value, ctx, std::get<N>(value.tuple)...);
   }
 
@@ -371,14 +370,14 @@ FMT_CONSTEXPR tuple_arg_join<wchar_t, T...> join(const std::tuple<T...>& tuple,
   \endrst
  */
 template <typename T>
-arg_join<internal::iterator_t<const std::initializer_list<T>>, char> join(
-    std::initializer_list<T> list, string_view sep) {
+arg_join<const T*, const T*, char> join(std::initializer_list<T> list,
+                                        string_view sep) {
   return join(std::begin(list), std::end(list), sep);
 }
 
 template <typename T>
-arg_join<internal::iterator_t<const std::initializer_list<T>>, wchar_t> join(
-    std::initializer_list<T> list, wstring_view sep) {
+arg_join<const T*, const T*, wchar_t> join(std::initializer_list<T> list,
+                                           wstring_view sep) {
   return join(std::begin(list), std::end(list), sep);
 }
 
diff --git a/src/format.cc b/src/format.cc
index 9a9abf8d..a64a1f38 100644
--- a/src/format.cc
+++ b/src/format.cc
@@ -8,12 +8,12 @@
 #include "fmt/format-inl.h"
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 
 template <typename T>
 int format_float(char* buf, std::size_t size, const char* format, int precision,
                  T value) {
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+#ifdef FMT_FUZZ
   if (precision > 100000)
     throw std::runtime_error(
         "fuzz mode - avoid large allocation inside snprintf");
@@ -23,154 +23,47 @@ int format_float(char* buf, std::size_t size, const char* format, int precision,
   return precision < 0 ? snprintf_ptr(buf, size, format, value)
                        : snprintf_ptr(buf, size, format, precision, value);
 }
-struct sprintf_specs {
-  int precision;
-  char type;
-  bool alt : 1;
+}  // namespace detail
 
-  template <typename Char>
-  constexpr sprintf_specs(basic_format_specs<Char> specs)
-      : precision(specs.precision), type(specs.type), alt(specs.alt) {}
-
-  constexpr bool has_precision() const { return precision >= 0; }
-};
-
-// This is deprecated and is kept only to preserve ABI compatibility.
-template <typename Double>
-char* sprintf_format(Double value, internal::buffer<char>& buf,
-                     sprintf_specs specs) {
-  // Buffer capacity must be non-zero, otherwise MSVC's vsnprintf_s will fail.
-  FMT_ASSERT(buf.capacity() != 0, "empty buffer");
-
-  // Build format string.
-  enum { max_format_size = 10 };  // longest format: %#-*.*Lg
-  char format[max_format_size];
-  char* format_ptr = format;
-  *format_ptr++ = '%';
-  if (specs.alt || !specs.type) *format_ptr++ = '#';
-  if (specs.precision >= 0) {
-    *format_ptr++ = '.';
-    *format_ptr++ = '*';
-  }
-  if (std::is_same<Double, long double>::value) *format_ptr++ = 'L';
-
-  char type = specs.type;
-
-  if (type == '%')
-    type = 'f';
-  else if (type == 0 || type == 'n')
-    type = 'g';
-#if FMT_MSC_VER
-  if (type == 'F') {
-    // MSVC's printf doesn't support 'F'.
-    type = 'f';
-  }
-#endif
-  *format_ptr++ = type;
-  *format_ptr = '\0';
-
-  // Format using snprintf.
-  char* start = nullptr;
-  char* decimal_point_pos = nullptr;
-  for (;;) {
-    std::size_t buffer_size = buf.capacity();
-    start = &buf[0];
-    int result =
-        format_float(start, buffer_size, format, specs.precision, value);
-    if (result >= 0) {
-      unsigned n = internal::to_unsigned(result);
-      if (n < buf.capacity()) {
-        // Find the decimal point.
-        auto p = buf.data(), end = p + n;
-        if (*p == '+' || *p == '-') ++p;
-        if (specs.type != 'a' && specs.type != 'A') {
-          while (p < end && *p >= '0' && *p <= '9') ++p;
-          if (p < end && *p != 'e' && *p != 'E') {
-            decimal_point_pos = p;
-            if (!specs.type) {
-              // Keep only one trailing zero after the decimal point.
-              ++p;
-              if (*p == '0') ++p;
-              while (p != end && *p >= '1' && *p <= '9') ++p;
-              char* where = p;
-              while (p != end && *p == '0') ++p;
-              if (p == end || *p < '0' || *p > '9') {
-                if (p != end) std::memmove(where, p, to_unsigned(end - p));
-                n -= static_cast<unsigned>(p - where);
-              }
-            }
-          }
-        }
-        buf.resize(n);
-        break;  // The buffer is large enough - continue with formatting.
-      }
-      buf.reserve(n + 1);
-    } else {
-      // If result is negative we ask to increase the capacity by at least 1,
-      // but as std::vector, the buffer grows exponentially.
-      buf.reserve(buf.capacity() + 1);
-    }
-  }
-  return decimal_point_pos;
-}
-}  // namespace internal
-
-template FMT_API char* internal::sprintf_format(double, internal::buffer<char>&,
-                                                sprintf_specs);
-template FMT_API char* internal::sprintf_format(long double,
-                                                internal::buffer<char>&,
-                                                sprintf_specs);
-
-template struct FMT_INSTANTIATION_DEF_API internal::basic_data<void>;
+template struct FMT_INSTANTIATION_DEF_API detail::basic_data<void>;
 
 // Workaround a bug in MSVC2013 that prevents instantiation of format_float.
-int (*instantiate_format_float)(double, int, internal::float_specs,
-                                internal::buffer<char>&) =
-    internal::format_float;
+int (*instantiate_format_float)(double, int, detail::float_specs,
+                                detail::buffer<char>&) = detail::format_float;
 
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
-template FMT_API internal::locale_ref::locale_ref(const std::locale& loc);
-template FMT_API std::locale internal::locale_ref::get<std::locale>() const;
+template FMT_API detail::locale_ref::locale_ref(const std::locale& loc);
+template FMT_API std::locale detail::locale_ref::get<std::locale>() const;
 #endif
 
 // Explicit instantiations for char.
 
-template FMT_API std::string internal::grouping_impl<char>(locale_ref);
-template FMT_API char internal::thousands_sep_impl(locale_ref);
-template FMT_API char internal::decimal_point_impl(locale_ref);
+template FMT_API std::string detail::grouping_impl<char>(locale_ref);
+template FMT_API char detail::thousands_sep_impl(locale_ref);
+template FMT_API char detail::decimal_point_impl(locale_ref);
 
-template FMT_API void internal::buffer<char>::append(const char*, const char*);
+template FMT_API void detail::buffer<char>::append(const char*, const char*);
 
-template FMT_API void internal::arg_map<format_context>::init(
-    const basic_format_args<format_context>& args);
+template FMT_API FMT_BUFFER_CONTEXT(char)::iterator detail::vformat_to(
+    detail::buffer<char>&, string_view,
+    basic_format_args<FMT_BUFFER_CONTEXT(char)>);
 
-template FMT_API std::string internal::vformat<char>(
-    string_view, basic_format_args<format_context>);
-
-template FMT_API format_context::iterator internal::vformat_to(
-    internal::buffer<char>&, string_view, basic_format_args<format_context>);
-
-template FMT_API int internal::snprintf_float(double, int,
-                                              internal::float_specs,
-                                              internal::buffer<char>&);
-template FMT_API int internal::snprintf_float(long double, int,
-                                              internal::float_specs,
-                                              internal::buffer<char>&);
-template FMT_API int internal::format_float(double, int, internal::float_specs,
-                                            internal::buffer<char>&);
-template FMT_API int internal::format_float(long double, int,
-                                            internal::float_specs,
-                                            internal::buffer<char>&);
+template FMT_API int detail::snprintf_float(double, int, detail::float_specs,
+                                            detail::buffer<char>&);
+template FMT_API int detail::snprintf_float(long double, int,
+                                            detail::float_specs,
+                                            detail::buffer<char>&);
+template FMT_API int detail::format_float(double, int, detail::float_specs,
+                                          detail::buffer<char>&);
+template FMT_API int detail::format_float(long double, int, detail::float_specs,
+                                          detail::buffer<char>&);
 
 // Explicit instantiations for wchar_t.
 
-template FMT_API std::string internal::grouping_impl<wchar_t>(locale_ref);
-template FMT_API wchar_t internal::thousands_sep_impl(locale_ref);
-template FMT_API wchar_t internal::decimal_point_impl(locale_ref);
+template FMT_API std::string detail::grouping_impl<wchar_t>(locale_ref);
+template FMT_API wchar_t detail::thousands_sep_impl(locale_ref);
+template FMT_API wchar_t detail::decimal_point_impl(locale_ref);
 
-template FMT_API void internal::buffer<wchar_t>::append(const wchar_t*,
-                                                        const wchar_t*);
-
-template FMT_API std::wstring internal::vformat<wchar_t>(
-    wstring_view, basic_format_args<wformat_context>);
+template FMT_API void detail::buffer<wchar_t>::append(const wchar_t*,
+                                                      const wchar_t*);
 FMT_END_NAMESPACE
diff --git a/src/os.cc b/src/os.cc
index 10a372a4..386119db 100644
--- a/src/os.cc
+++ b/src/os.cc
@@ -73,14 +73,14 @@ inline std::size_t convert_rwcount(std::size_t count) { return count; }
 FMT_BEGIN_NAMESPACE
 
 #ifdef _WIN32
-internal::utf16_to_utf8::utf16_to_utf8(wstring_view s) {
+detail::utf16_to_utf8::utf16_to_utf8(wstring_view s) {
   if (int error_code = convert(s)) {
     FMT_THROW(windows_error(error_code,
                             "cannot convert string from UTF-16 to UTF-8"));
   }
 }
 
-int internal::utf16_to_utf8::convert(wstring_view s) {
+int detail::utf16_to_utf8::convert(wstring_view s) {
   if (s.size() > INT_MAX) return ERROR_INVALID_PARAMETER;
   int s_size = static_cast<int>(s.size());
   if (s_size == 0) {
@@ -105,13 +105,13 @@ void windows_error::init(int err_code, string_view format_str,
                          format_args args) {
   error_code_ = err_code;
   memory_buffer buffer;
-  internal::format_windows_error(buffer, err_code, vformat(format_str, args));
+  detail::format_windows_error(buffer, err_code, vformat(format_str, args));
   std::runtime_error& base = *this;
   base = std::runtime_error(to_string(buffer));
 }
 
-void internal::format_windows_error(internal::buffer<char>& out, int error_code,
-                                    string_view message) FMT_NOEXCEPT {
+void detail::format_windows_error(detail::buffer<char>& out, int error_code,
+                                  string_view message) FMT_NOEXCEPT {
   FMT_TRY {
     wmemory_buffer buf;
     buf.resize(inline_buffer_size);
@@ -124,10 +124,7 @@ void internal::format_windows_error(internal::buffer<char>& out, int error_code,
       if (result != 0) {
         utf16_to_utf8 utf8_message;
         if (utf8_message.convert(system_message) == ERROR_SUCCESS) {
-          internal::writer w(out);
-          w.write(message);
-          w.write(": ");
-          w.write(utf8_message);
+          format_to(std::back_inserter(out), "{}: {}", message, utf8_message);
           return;
         }
         break;
@@ -143,7 +140,7 @@ void internal::format_windows_error(internal::buffer<char>& out, int error_code,
 
 void report_windows_error(int error_code,
                           fmt::string_view message) FMT_NOEXCEPT {
-  report_error(internal::format_windows_error, error_code, message);
+  report_error(detail::format_windows_error, error_code, message);
 }
 #endif  // _WIN32
 
@@ -234,14 +231,14 @@ std::size_t file::read(void* buffer, std::size_t count) {
   RWResult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(read(fd_, buffer, convert_rwcount(count))));
   if (result < 0) FMT_THROW(system_error(errno, "cannot read from file"));
-  return internal::to_unsigned(result);
+  return detail::to_unsigned(result);
 }
 
 std::size_t file::write(const void* buffer, std::size_t count) {
   RWResult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(write(fd_, buffer, convert_rwcount(count))));
   if (result < 0) FMT_THROW(system_error(errno, "cannot write to file"));
-  return internal::to_unsigned(result);
+  return detail::to_unsigned(result);
 }
 
 file file::dup(int fd) {
@@ -292,7 +289,11 @@ void file::pipe(file& read_end, file& write_end) {
 
 buffered_file file::fdopen(const char* mode) {
   // Don't retry as fdopen doesn't return EINTR.
+  #if defined(__MINGW32__) && defined(_POSIX_)
+  FILE* f = ::fdopen(fd_, mode);
+  #else
   FILE* f = FMT_POSIX_CALL(fdopen(fd_, mode));
+  #endif
   if (!f)
     FMT_THROW(
         system_error(errno, "cannot associate stream with file descriptor"));
diff --git a/support/Vagrantfile b/support/Vagrantfile
index 24f166a1..f6b5f936 100644
--- a/support/Vagrantfile
+++ b/support/Vagrantfile
@@ -4,6 +4,7 @@
 # A vagrant config for testing against gcc-4.8.
 Vagrant.configure("2") do |config|
   config.vm.box = "ubuntu/xenial64"
+  config.disksize.size = '15GB'
 
   config.vm.provider "virtualbox" do |vb|
     vb.memory = "4096"
diff --git a/support/cmake/JoinPaths.cmake b/support/cmake/JoinPaths.cmake
new file mode 100644
index 00000000..32d6d668
--- /dev/null
+++ b/support/cmake/JoinPaths.cmake
@@ -0,0 +1,26 @@
+# This module provides function for joining paths
+# known from from most languages
+#
+# Original license:
+# SPDX-License-Identifier: (MIT OR CC0-1.0)
+# Explicit permission given to distribute this module under
+# the terms of the project as described in /LICENSE.rst.
+# Copyright 2020 Jan Tojnar
+# https://github.com/jtojnar/cmake-snips
+#
+# Modelled after Python’s os.path.join
+# https://docs.python.org/3.7/library/os.path.html#os.path.join
+# Windows not supported
+function(join_paths joined_path first_path_segment)
+    set(temp_path "${first_path_segment}")
+    foreach(current_segment IN LISTS ARGN)
+        if(NOT ("${current_segment}" STREQUAL ""))
+            if(IS_ABSOLUTE "${current_segment}")
+                set(temp_path "${current_segment}")
+            else()
+                set(temp_path "${temp_path}/${current_segment}")
+            endif()
+        endif()
+    endforeach()
+    set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()
diff --git a/support/cmake/fmt.pc.in b/support/cmake/fmt.pc.in
index 4e030afd..29976a8a 100644
--- a/support/cmake/fmt.pc.in
+++ b/support/cmake/fmt.pc.in
@@ -1,7 +1,7 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=@CMAKE_INSTALL_PREFIX@
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@libdir_for_pc_file@
+includedir=@includedir_for_pc_file@
 
 Name: fmt
 Description: A modern formatting library
diff --git a/support/manage.py b/support/manage.py
index 517759b3..9f270669 100755
--- a/support/manage.py
+++ b/support/manage.py
@@ -144,9 +144,33 @@ def update_site(env):
                 b.data = re.sub(pattern, r'doxygenfunction:: \1(int)', b.data)
                 b.data = b.data.replace('std::FILE*', 'std::FILE *')
                 b.data = b.data.replace('unsigned int', 'unsigned')
-                b.data = b.data.replace('operator""_', 'operator"" _')
-                b.data = b.data.replace(', size_t', ', std::size_t')
+                #b.data = b.data.replace('operator""_', 'operator"" _')
+                b.data = b.data.replace(
+                    'format_to_n(OutputIt, size_t, string_view, Args&&',
+                    'format_to_n(OutputIt, size_t, const S&, const Args&')
+                b.data = b.data.replace(
+                    'format_to_n(OutputIt, std::size_t, string_view, Args&&',
+                    'format_to_n(OutputIt, std::size_t, const S&, const Args&')
+                if version == ('3.0.2'):
+                    b.data = b.data.replace(
+                        'fprintf(std::ostream&', 'fprintf(std::ostream &')
+                if version == ('5.3.0'):
+                    b.data = b.data.replace(
+                        'format_to(OutputIt, const S&, const Args&...)',
+                        'format_to(OutputIt, const S &, const Args &...)')
+                if version.startswith('5.') or version.startswith('6.'):
+                    b.data = b.data.replace(', size_t', ', std::size_t')
+                if version.startswith('7.'):
+                    b.data = b.data.replace(', std::size_t', ', size_t')
+                    b.data = b.data.replace('join(It, It', 'join(It, Sentinel')
                 b.data = b.data.replace('aa long', 'a long')
+                b.data = b.data.replace('serveral', 'several')
+                if version.startswith('6.2.'):
+                    b.data = b.data.replace(
+                        'vformat(const S&, basic_format_args<' +
+                        'buffer_context<Char>>)',
+                        'vformat(const S&, basic_format_args<' +
+                        'buffer_context<type_identity_t<Char>>>)')
         # Fix a broken link in index.rst.
         index = os.path.join(target_doc_dir, 'index.rst')
         with rewrite(index) as b:
diff --git a/test/chrono-test.cc b/test/chrono-test.cc
index 828a8aee..b876c151 100644
--- a/test/chrono-test.cc
+++ b/test/chrono-test.cc
@@ -10,10 +10,11 @@
 #endif
 
 #include "fmt/chrono.h"
-#include "gtest-extra.h"
 
 #include <iomanip>
 
+#include "gtest-extra.h"
+
 std::tm make_tm() {
   auto time = std::tm();
   time.tm_mday = 1;
diff --git a/test/color-test.cc b/test/color-test.cc
index c1113a2e..454a0660 100644
--- a/test/color-test.cc
+++ b/test/color-test.cc
@@ -6,6 +6,7 @@
 // For the license information refer to format.h.
 
 #include "fmt/color.h"
+
 #include "gtest-extra.h"
 
 TEST(ColorsTest, ColorsPrint) {
diff --git a/test/compile-test.cc b/test/compile-test.cc
index 13bef488..a47cea54 100644
--- a/test/compile-test.cc
+++ b/test/compile-test.cc
@@ -6,6 +6,7 @@
 // For the license information refer to format.h.
 
 #include <stdint.h>
+
 #include <cctype>
 #include <cfloat>
 #include <climits>
@@ -39,8 +40,8 @@ using testing::StrictMock;
 #if FMT_USE_CONSTEXPR
 template <unsigned EXPECTED_PARTS_COUNT, typename Format>
 void check_prepared_parts_type(Format format) {
-  typedef fmt::internal::compiled_format_base<decltype(format)> provider;
-  typedef fmt::internal::format_part<char>
+  typedef fmt::detail::compiled_format_base<decltype(format)> provider;
+  typedef fmt::detail::format_part<char>
       expected_parts_type[EXPECTED_PARTS_COUNT];
   static_assert(std::is_same<typename provider::parts_container,
                              expected_parts_type>::value,
@@ -66,46 +67,37 @@ TEST(CompileTest, CompileTimePreparedPartsTypeProvider) {
 #endif
 
 TEST(CompileTest, PassStringLiteralFormat) {
-  const auto prepared = fmt::compile<int>("test {}");
+  const auto prepared = fmt::detail::compile<int>("test {}");
   EXPECT_EQ("test 42", fmt::format(prepared, 42));
-  const auto wprepared = fmt::compile<int>(L"test {}");
+  const auto wprepared = fmt::detail::compile<int>(L"test {}");
   EXPECT_EQ(L"test 42", fmt::format(wprepared, 42));
 }
 
-#if FMT_USE_CONSTEXPR
-TEST(CompileTest, PassCompileString) {
-  const auto prepared = fmt::compile<int>(FMT_STRING("test {}"));
-  EXPECT_EQ("test 42", fmt::format(prepared, 42));
-  const auto wprepared = fmt::compile<int>(FMT_STRING(L"test {}"));
-  EXPECT_EQ(L"test 42", fmt::format(wprepared, 42));
-}
-#endif
-
 TEST(CompileTest, FormatToArrayOfChars) {
   char buffer[32] = {0};
-  const auto prepared = fmt::compile<int>("4{}");
-  fmt::format_to(fmt::internal::make_checked(buffer, 32), prepared, 2);
+  const auto prepared = fmt::detail::compile<int>("4{}");
+  fmt::format_to(fmt::detail::make_checked(buffer, 32), prepared, 2);
   EXPECT_EQ(std::string("42"), buffer);
   wchar_t wbuffer[32] = {0};
-  const auto wprepared = fmt::compile<int>(L"4{}");
-  fmt::format_to(fmt::internal::make_checked(wbuffer, 32), wprepared, 2);
+  const auto wprepared = fmt::detail::compile<int>(L"4{}");
+  fmt::format_to(fmt::detail::make_checked(wbuffer, 32), wprepared, 2);
   EXPECT_EQ(std::wstring(L"42"), wbuffer);
 }
 
 TEST(CompileTest, FormatToIterator) {
   std::string s(2, ' ');
-  const auto prepared = fmt::compile<int>("4{}");
+  const auto prepared = fmt::detail::compile<int>("4{}");
   fmt::format_to(s.begin(), prepared, 2);
   EXPECT_EQ("42", s);
   std::wstring ws(2, L' ');
-  const auto wprepared = fmt::compile<int>(L"4{}");
+  const auto wprepared = fmt::detail::compile<int>(L"4{}");
   fmt::format_to(ws.begin(), wprepared, 2);
   EXPECT_EQ(L"42", ws);
 }
 
 TEST(CompileTest, FormatToN) {
   char buf[5];
-  auto f = fmt::compile<int>("{:10}");
+  auto f = fmt::detail::compile<int>("{:10}");
   auto result = fmt::format_to_n(buf, 5, f, 42);
   EXPECT_EQ(result.size, 10);
   EXPECT_EQ(result.out, buf + 5);
@@ -113,12 +105,12 @@ TEST(CompileTest, FormatToN) {
 }
 
 TEST(CompileTest, FormattedSize) {
-  auto f = fmt::compile<int>("{:10}");
+  auto f = fmt::detail::compile<int>("{:10}");
   EXPECT_EQ(fmt::formatted_size(f, 42), 10);
 }
 
 TEST(CompileTest, MultipleTypes) {
-  auto f = fmt::compile<int, int>("{} {}");
+  auto f = fmt::detail::compile<int, int>("{} {}");
   EXPECT_EQ(fmt::format(f, 42, 42), "42 42");
 }
 
@@ -126,18 +118,49 @@ struct formattable {};
 
 FMT_BEGIN_NAMESPACE
 template <> struct formatter<formattable> : formatter<const char*> {
-  auto format(formattable, format_context& ctx) -> decltype(ctx.out()) {
+  template <typename FormatContext>
+  auto format(formattable, FormatContext& ctx) -> decltype(ctx.out()) {
     return formatter<const char*>::format("foo", ctx);
   }
 };
 FMT_END_NAMESPACE
 
 TEST(CompileTest, FormatUserDefinedType) {
-  auto f = fmt::compile<formattable>("{}");
+  auto f = fmt::detail::compile<formattable>("{}");
   EXPECT_EQ(fmt::format(f, formattable()), "foo");
 }
 
 TEST(CompileTest, EmptyFormatString) {
-  auto f = fmt::compile<>("");
+  auto f = fmt::detail::compile<>("");
   EXPECT_EQ(fmt::format(f), "");
 }
+
+#ifdef __cpp_if_constexpr
+TEST(CompileTest, FormatDefault) {
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42));
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42u));
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42ll));
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), 42ull));
+  EXPECT_EQ("true", fmt::format(FMT_COMPILE("{}"), true));
+  EXPECT_EQ("x", fmt::format(FMT_COMPILE("{}"), 'x'));
+  EXPECT_EQ("4.2", fmt::format(FMT_COMPILE("{}"), 4.2));
+  EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), "foo"));
+  EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), std::string("foo")));
+  EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), formattable()));
+}
+
+TEST(CompileTest, FormatSpecs) {
+  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{:x}"), 0x42));
+}
+
+TEST(CompileTest, FormatTo) {
+  char buf[8];
+  auto end = fmt::format_to(buf, FMT_COMPILE("{}"), 42);
+  *end = '\0';
+  EXPECT_STREQ("42", buf);
+}
+
+TEST(CompileTest, TextAndArg) {
+  EXPECT_EQ(">>>42<<<", fmt::format(FMT_COMPILE(">>>{}<<<"), 42));
+}
+#endif
diff --git a/test/core-test.cc b/test/core-test.cc
index f19d0423..8a1ea83b 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -30,8 +30,8 @@
 
 using fmt::basic_format_arg;
 using fmt::string_view;
-using fmt::internal::buffer;
-using fmt::internal::value;
+using fmt::detail::buffer;
+using fmt::detail::value;
 
 using testing::_;
 using testing::StrictMock;
@@ -42,7 +42,7 @@ struct test_struct {};
 
 template <typename Context, typename T>
 basic_format_arg<Context> make_arg(const T& value) {
-  return fmt::internal::make_arg<Context>(value);
+  return fmt::detail::make_arg<Context>(value);
 }
 }  // namespace
 
@@ -83,20 +83,20 @@ TEST(BufferTest, Nonmoveable) {
 
 // A test buffer with a dummy grow method.
 template <typename T> struct test_buffer : buffer<T> {
-  void grow(std::size_t capacity) { this->set(nullptr, capacity); }
+  void grow(size_t capacity) { this->set(nullptr, capacity); }
 };
 
 template <typename T> struct mock_buffer : buffer<T> {
-  MOCK_METHOD1(do_grow, void(std::size_t capacity));
+  MOCK_METHOD1(do_grow, void(size_t capacity));
 
-  void grow(std::size_t capacity) {
+  void grow(size_t capacity) {
     this->set(this->data(), capacity);
     do_grow(capacity);
   }
 
   mock_buffer() {}
   mock_buffer(T* data) { this->set(data, 0); }
-  mock_buffer(T* data, std::size_t capacity) { this->set(data, capacity); }
+  mock_buffer(T* data, size_t capacity) { this->set(data, capacity); }
 };
 
 TEST(BufferTest, Ctor) {
@@ -115,7 +115,7 @@ TEST(BufferTest, Ctor) {
   }
   {
     int dummy;
-    std::size_t capacity = std::numeric_limits<std::size_t>::max();
+    size_t capacity = std::numeric_limits<size_t>::max();
     mock_buffer<int> buffer(&dummy, capacity);
     EXPECT_EQ(&dummy, &buffer[0]);
     EXPECT_EQ(static_cast<size_t>(0), buffer.size());
@@ -148,7 +148,7 @@ TEST(BufferTest, Access) {
   EXPECT_EQ(11, buffer[0]);
   buffer[3] = 42;
   EXPECT_EQ(42, *(&buffer[0] + 3));
-  const fmt::internal::buffer<char>& const_buffer = buffer;
+  const fmt::detail::buffer<char>& const_buffer = buffer;
   EXPECT_EQ(42, const_buffer[3]);
 }
 
@@ -210,7 +210,8 @@ TEST(ArgTest, FormatArgs) {
 }
 
 struct custom_context {
-  typedef char char_type;
+  using char_type = char;
+  using parse_context_type = fmt::format_parse_context;
 
   template <typename T> struct formatter_type {
     template <typename ParseContext>
@@ -233,20 +234,20 @@ struct custom_context {
 
 TEST(ArgTest, MakeValueWithCustomContext) {
   test_struct t;
-  fmt::internal::value<custom_context> arg(
-      fmt::internal::arg_mapper<custom_context>().map(t));
+  fmt::detail::value<custom_context> arg(
+      fmt::detail::arg_mapper<custom_context>().map(t));
   custom_context ctx = {false, fmt::format_parse_context("")};
   arg.custom.format(&t, ctx.parse_context(), ctx);
   EXPECT_TRUE(ctx.called);
 }
 
 FMT_BEGIN_NAMESPACE
-namespace internal {
+namespace detail {
 template <typename Char>
 bool operator==(custom_value<Char> lhs, custom_value<Char> rhs) {
   return lhs.value == rhs.value;
 }
-}  // namespace internal
+}  // namespace detail
 FMT_END_NAMESPACE
 
 // Use a unique result type to make sure that there are no undesirable
@@ -371,12 +372,12 @@ TEST(ArgTest, PointerArg) {
 struct check_custom {
   test_result operator()(
       fmt::basic_format_arg<fmt::format_context>::handle h) const {
-    struct test_buffer : fmt::internal::buffer<char> {
+    struct test_buffer : fmt::detail::buffer<char> {
       char data[10];
-      test_buffer() : fmt::internal::buffer<char>(data, 0, 10) {}
-      void grow(std::size_t) {}
+      test_buffer() : fmt::detail::buffer<char>(data, 0, 10) {}
+      void grow(size_t) {}
     } buffer;
-    fmt::internal::buffer<char>& base = buffer;
+    fmt::detail::buffer<char>& base = buffer;
     fmt::format_parse_context parse_ctx("");
     fmt::format_context ctx(std::back_inserter(base), fmt::format_args());
     h.format(parse_ctx, ctx);
@@ -455,6 +456,25 @@ TEST(FormatDynArgsTest, CustomFormat) {
   EXPECT_EQ("cust=0 and cust=1 and cust=3", result);
 }
 
+TEST(FormatDynArgsTest, NamedInt) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.push_back(fmt::arg("a1", 42));
+  std::string result = fmt::vformat("{a1}", store);
+  EXPECT_EQ("42", result);
+}
+
+TEST(FormatDynArgsTest, NamedStrings) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  char str[]{"1234567890"};
+  store.push_back(fmt::arg("a1", str));
+  store.push_back(fmt::arg("a2", std::cref(str)));
+  str[0] = 'X';
+
+  std::string result = fmt::vformat("{a1} and {a2}", store);
+
+  EXPECT_EQ("1234567890 and X234567890", result);
+}
+
 TEST(FormatDynArgsTest, NamedArgByRef) {
   fmt::dynamic_format_arg_store<fmt::format_context> store;
 
@@ -469,12 +489,53 @@ TEST(FormatDynArgsTest, NamedArgByRef) {
   // storages.
   int a1_val{42};
   auto a1 = fmt::arg("a1_", a1_val);
+  store.push_back("abc");
+  store.push_back(1.5f);
   store.push_back(std::cref(a1));
 
-  std::string result = fmt::vformat("{a1_}",  // and {} and {}",
-                                    store);
+  std::string result = fmt::vformat("{a1_} and {} and {} and {}", store);
 
+  EXPECT_EQ("42 and abc and 1.5 and 42", result);
+}
+
+TEST(FormatDynArgsTest, NamedCustomFormat) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  custom_type c{};
+  store.push_back(fmt::arg("c1", c));
+  ++c.i;
+  store.push_back(fmt::arg("c2", c));
+  ++c.i;
+  store.push_back(fmt::arg("c_ref", std::cref(c)));
+  ++c.i;
+
+  std::string result = fmt::vformat("{c1} and {c2} and {c_ref}", store);
+  EXPECT_EQ("cust=0 and cust=1 and cust=3", result);
+}
+
+TEST(FormatDynArgsTest, Clear) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.push_back(42);
+
+  std::string result = fmt::vformat("{}", store);
   EXPECT_EQ("42", result);
+
+  store.push_back(43);
+  result = fmt::vformat("{} and {}", store);
+  EXPECT_EQ("42 and 43", result);
+
+  store.clear();
+  store.push_back(44);
+  result = fmt::vformat("{}", store);
+  EXPECT_EQ("44", result);
+}
+
+TEST(FormatDynArgsTest, Reserve) {
+  fmt::dynamic_format_arg_store<fmt::format_context> store;
+  store.reserve(2, 1);
+  store.push_back(1.5f);
+  store.push_back(fmt::arg("a1", 42));
+  std::string result = fmt::vformat("{a1} and {}", store);
+  EXPECT_EQ("42 and 1.5", result);
 }
 
 struct copy_throwable {
@@ -517,9 +578,9 @@ TEST(StringViewTest, Length) {
 // Check string_view's comparison operator.
 template <template <typename> class Op> void check_op() {
   const char* inputs[] = {"foo", "fop", "fo"};
-  std::size_t num_inputs = sizeof(inputs) / sizeof(*inputs);
-  for (std::size_t i = 0; i < num_inputs; ++i) {
-    for (std::size_t j = 0; j < num_inputs; ++j) {
+  size_t num_inputs = sizeof(inputs) / sizeof(*inputs);
+  for (size_t i = 0; i < num_inputs; ++i) {
+    for (size_t j = 0; j < num_inputs; ++j) {
       string_view lhs(inputs[i]), rhs(inputs[j]);
       EXPECT_EQ(Op<int>()(lhs.compare(rhs), 0), Op<string_view>()(lhs, rhs));
     }
@@ -605,7 +666,7 @@ template <typename Char> class my_string {
  public:
   my_string(const Char* s) : s_(s) {}
   const Char* data() const FMT_NOEXCEPT { return s_.data(); }
-  std::size_t length() const FMT_NOEXCEPT { return s_.size(); }
+  size_t length() const FMT_NOEXCEPT { return s_.size(); }
   operator const Char*() const { return s_.c_str(); }
 
  private:
@@ -621,23 +682,6 @@ inline fmt::basic_string_view<Char> to_string_view(const my_string<Char>& s)
 struct non_string {};
 }  // namespace my_ns
 
-namespace FakeQt {
-class QString {
- public:
-  QString(const wchar_t* s) : s_(std::make_shared<std::wstring>(s)) {}
-  const wchar_t* utf16() const FMT_NOEXCEPT { return s_->data(); }
-  int size() const FMT_NOEXCEPT { return static_cast<int>(s_->size()); }
-
- private:
-  std::shared_ptr<std::wstring> s_;
-};
-
-inline fmt::basic_string_view<wchar_t> to_string_view(const QString& s)
-    FMT_NOEXCEPT {
-  return {s.utf16(), static_cast<std::size_t>(s.size())};
-}
-}  // namespace FakeQt
-
 template <typename T> class IsStringTest : public testing::Test {};
 
 typedef ::testing::Types<char, wchar_t, char16_t, char32_t> StringCharTypes;
@@ -649,21 +693,19 @@ struct derived_from_string_view : fmt::basic_string_view<Char> {};
 }  // namespace
 
 TYPED_TEST(IsStringTest, IsString) {
-  EXPECT_TRUE(fmt::internal::is_string<TypeParam*>::value);
-  EXPECT_TRUE(fmt::internal::is_string<const TypeParam*>::value);
-  EXPECT_TRUE(fmt::internal::is_string<TypeParam[2]>::value);
-  EXPECT_TRUE(fmt::internal::is_string<const TypeParam[2]>::value);
-  EXPECT_TRUE(fmt::internal::is_string<std::basic_string<TypeParam>>::value);
+  EXPECT_TRUE(fmt::detail::is_string<TypeParam*>::value);
+  EXPECT_TRUE(fmt::detail::is_string<const TypeParam*>::value);
+  EXPECT_TRUE(fmt::detail::is_string<TypeParam[2]>::value);
+  EXPECT_TRUE(fmt::detail::is_string<const TypeParam[2]>::value);
+  EXPECT_TRUE(fmt::detail::is_string<std::basic_string<TypeParam>>::value);
+  EXPECT_TRUE(fmt::detail::is_string<fmt::basic_string_view<TypeParam>>::value);
   EXPECT_TRUE(
-      fmt::internal::is_string<fmt::basic_string_view<TypeParam>>::value);
-  EXPECT_TRUE(
-      fmt::internal::is_string<derived_from_string_view<TypeParam>>::value);
-  using string_view = fmt::internal::std_string_view<TypeParam>;
+      fmt::detail::is_string<derived_from_string_view<TypeParam>>::value);
+  using string_view = fmt::detail::std_string_view<TypeParam>;
   EXPECT_TRUE(std::is_empty<string_view>::value !=
-              fmt::internal::is_string<string_view>::value);
-  EXPECT_TRUE(fmt::internal::is_string<my_ns::my_string<TypeParam>>::value);
-  EXPECT_FALSE(fmt::internal::is_string<my_ns::non_string>::value);
-  EXPECT_TRUE(fmt::internal::is_string<FakeQt::QString>::value);
+              fmt::detail::is_string<string_view>::value);
+  EXPECT_TRUE(fmt::detail::is_string<my_ns::my_string<TypeParam>>::value);
+  EXPECT_FALSE(fmt::detail::is_string<my_ns::non_string>::value);
 }
 
 TEST(CoreTest, Format) {
@@ -686,33 +728,16 @@ TEST(CoreTest, FormatTo) {
 
 TEST(CoreTest, ToStringViewForeignStrings) {
   using namespace my_ns;
-  using namespace FakeQt;
   EXPECT_EQ(to_string_view(my_string<char>("42")), "42");
-  EXPECT_EQ(to_string_view(my_string<wchar_t>(L"42")), L"42");
-  EXPECT_EQ(to_string_view(QString(L"42")), L"42");
-  fmt::internal::type type =
-      fmt::internal::mapped_type_constant<my_string<char>,
-                                          fmt::format_context>::value;
-  EXPECT_EQ(type, fmt::internal::type::string_type);
-  type = fmt::internal::mapped_type_constant<my_string<wchar_t>,
-                                             fmt::wformat_context>::value;
-  EXPECT_EQ(type, fmt::internal::type::string_type);
-  type =
-      fmt::internal::mapped_type_constant<QString, fmt::wformat_context>::value;
-  EXPECT_EQ(type, fmt::internal::type::string_type);
-  // Does not compile: only wide format contexts are compatible with QString!
-  // type = fmt::internal::mapped_type_constant<QString,
-  // fmt::format_context>::value;
+  fmt::detail::type type =
+      fmt::detail::mapped_type_constant<my_string<char>,
+                                        fmt::format_context>::value;
+  EXPECT_EQ(type, fmt::detail::type::string_type);
 }
 
 TEST(CoreTest, FormatForeignStrings) {
   using namespace my_ns;
-  using namespace FakeQt;
   EXPECT_EQ(fmt::format(my_string<char>("{}"), 42), "42");
-  EXPECT_EQ(fmt::format(my_string<wchar_t>(L"{}"), 42), L"42");
-  EXPECT_EQ(fmt::format(QString(L"{}"), 42), L"42");
-  EXPECT_EQ(fmt::format(QString(L"{}"), my_string<wchar_t>(L"42")), L"42");
-  EXPECT_EQ(fmt::format(my_string<wchar_t>(L"{}"), QString(L"42")), L"42");
 }
 
 struct implicitly_convertible_to_string {
@@ -747,15 +772,6 @@ TEST(FormatterTest, FormatExplicitlyConvertibleToStdStringView) {
             fmt::format("{}", explicitly_convertible_to_std_string_view()));
 }
 #  endif
-
-struct explicitly_convertible_to_wstring_view {
-  explicit operator fmt::wstring_view() const { return L"foo"; }
-};
-
-TEST(FormatterTest, FormatExplicitlyConvertibleToWStringView) {
-  EXPECT_EQ(L"foo",
-            fmt::format(L"{}", explicitly_convertible_to_wstring_view()));
-}
 #endif
 
 struct disabled_rvalue_conversion {
diff --git a/test/custom-formatter-test.cc b/test/custom-formatter-test.cc
index 36007cae..1b0c1e13 100644
--- a/test/custom-formatter-test.cc
+++ b/test/custom-formatter-test.cc
@@ -18,14 +18,14 @@
 // A custom argument formatter that doesn't print `-` for floating-point values
 // rounded to 0.
 class custom_arg_formatter
-    : public fmt::arg_formatter<fmt::buffer_range<char>> {
+    : public fmt::detail::arg_formatter<fmt::format_context::iterator, char> {
  public:
-  using range = fmt::buffer_range<char>;
-  typedef fmt::arg_formatter<range> base;
+  using base = fmt::detail::arg_formatter<fmt::format_context::iterator, char>;
 
   custom_arg_formatter(fmt::format_context& ctx,
                        fmt::format_parse_context* parse_ctx,
-                       fmt::format_specs* s = nullptr)
+                       fmt::format_specs* s = nullptr,
+                       const char* = nullptr)
       : base(ctx, parse_ctx, s) {}
 
   using base::operator();
@@ -39,8 +39,10 @@ class custom_arg_formatter
 
 std::string custom_vformat(fmt::string_view format_str, fmt::format_args args) {
   fmt::memory_buffer buffer;
+  fmt::detail::buffer<char>& base = buffer;
   // Pass custom argument formatter as a template arg to vwrite.
-  fmt::vformat_to<custom_arg_formatter>(buffer, format_str, args);
+  fmt::vformat_to<custom_arg_formatter>(std::back_inserter(base), format_str,
+                                        args);
   return std::string(buffer.data(), buffer.size());
 }
 
diff --git a/test/format b/test/format
index 62fa3167..11c58b96 100644
--- a/test/format
+++ b/test/format
@@ -38,9 +38,9 @@ namespace std {
   
   template<class Out, class charT> class basic_format_context;
   using format_context = basic_format_context<
-    /* unspecified */ std::back_insert_iterator<fmt::internal::buffer<char>>, char>;
+    /* unspecified */ std::back_insert_iterator<fmt::detail::buffer<char>>, char>;
   using wformat_context = basic_format_context<
-    /* unspecified */ std::back_insert_iterator<fmt::internal::buffer<wchar_t>>, wchar_t>;
+    /* unspecified */ std::back_insert_iterator<fmt::detail::buffer<wchar_t>>, wchar_t>;
 
   template<class T, class charT = char> struct formatter {
     formatter() = delete;
@@ -219,7 +219,7 @@ namespace std {
 
     // Implementation details:
     using format_arg = basic_format_arg<basic_format_context>;
-    basic_format_context(Out out, basic_format_args<basic_format_context> args, fmt::internal::locale_ref)
+    basic_format_context(Out out, basic_format_args<basic_format_context> args, fmt::detail::locale_ref)
     : args_(args), out_(out) {}
     detail::error_handler error_handler() const { return {}; }
     basic_format_arg<basic_format_context> arg(fmt::basic_string_view<charT>) const {
@@ -488,22 +488,21 @@ template<class... Args>
 namespace std {
 namespace detail {
 
-template <typename Range>
+template <typename OutputIt, typename Char>
 class arg_formatter
-    : public fmt::internal::arg_formatter_base<Range, error_handler> {
+    : public fmt::detail::arg_formatter_base<OutputIt, Char, error_handler> {
  private:
-  using char_type = typename Range::value_type;
-  using base = fmt::internal::arg_formatter_base<Range, error_handler>;
-  using format_context = std::basic_format_context<typename base::iterator, char_type>;
-  using parse_context = basic_format_parse_context<char_type>;
+  using char_type = Char;
+  using base = fmt::detail::arg_formatter_base<OutputIt, Char, error_handler>;
+  using format_context = std::basic_format_context<OutputIt, Char>;
+  using parse_context = basic_format_parse_context<Char>;
 
   parse_context* parse_ctx_;
   format_context& ctx_;
 
  public:
-  typedef Range range;
-  typedef typename base::iterator iterator;
-  typedef typename base::format_specs format_specs;
+  using iterator = OutputIt;
+  using format_specs = typename base::format_specs;
 
   /**
     \rst
@@ -513,7 +512,7 @@ class arg_formatter
     \endrst
    */
   arg_formatter(format_context& ctx, parse_context* parse_ctx = nullptr, fmt::format_specs* spec = nullptr)
-      : base(Range(ctx.out()), spec, {}), parse_ctx_(parse_ctx), ctx_(ctx) {}
+      : base(ctx.out(), spec, {}), parse_ctx_(parse_ctx), ctx_(ctx) {}
 
   using base::operator();
 
@@ -529,36 +528,36 @@ class arg_formatter
 };
 
 template <typename Context>
-inline fmt::internal::type get_type(basic_format_arg<Context> arg) {
+inline fmt::detail::type get_type(basic_format_arg<Context> arg) {
   return visit_format_arg([&] (auto val) {
     using char_type = typename Context::char_type;
     using T = decltype(val);
     if (std::is_same_v<T, monostate>)
-      return fmt::internal::type::none_type;
+      return fmt::detail::type::none_type;
     if (std::is_same_v<T, bool>)
-      return fmt::internal::type::bool_type;
+      return fmt::detail::type::bool_type;
     if (std::is_same_v<T, char_type>)
-      return fmt::internal::type::char_type;
+      return fmt::detail::type::char_type;
     if (std::is_same_v<T, int>)
-      return fmt::internal::type::int_type;
+      return fmt::detail::type::int_type;
     if (std::is_same_v<T, unsigned int>)
-      return fmt::internal::type::uint_type;
+      return fmt::detail::type::uint_type;
     if (std::is_same_v<T, long long int>)
-      return fmt::internal::type::long_long_type;
+      return fmt::detail::type::long_long_type;
     if (std::is_same_v<T, unsigned long long int>)
-      return fmt::internal::type::ulong_long_type;
+      return fmt::detail::type::ulong_long_type;
     if (std::is_same_v<T, double>)
-      return fmt::internal::type::double_type;
+      return fmt::detail::type::double_type;
     if (std::is_same_v<T, long double>)
-      return fmt::internal::type::long_double_type;
+      return fmt::detail::type::long_double_type;
     if (std::is_same_v<T, const char_type*>)
-      return fmt::internal::type::cstring_type;
+      return fmt::detail::type::cstring_type;
     if (std::is_same_v<T, basic_string_view<char_type>>)
-      return fmt::internal::type::string_type;
+      return fmt::detail::type::string_type;
     if (std::is_same_v<T, const void*>)
-      return fmt::internal::type::pointer_type;
+      return fmt::detail::type::pointer_type;
     assert(get_value(arg).index() == 12);
-    return fmt::internal::type::custom_type;
+    return fmt::detail::type::custom_type;
   }, arg);
 }
 
@@ -582,45 +581,42 @@ class custom_formatter {
 
 template <typename ArgFormatter, typename Char, typename Context>
 struct format_handler : detail::error_handler {
-  typedef typename ArgFormatter::range range;
+  using iterator = typename ArgFormatter::iterator;
 
-  format_handler(range r, basic_string_view<Char> str,
+  format_handler(iterator out, basic_string_view<Char> str,
                  basic_format_args<Context> format_args,
-                 fmt::internal::locale_ref loc)
-      : parse_ctx(str), context(r.begin(), format_args, loc) {}
+                 fmt::detail::locale_ref loc)
+      : parse_ctx(str), context(out, format_args, loc) {}
 
   void on_text(const Char* begin, const Char* end) {
-    auto size = fmt::internal::to_unsigned(end - begin);
+    auto size = fmt::detail::to_unsigned(end - begin);
     auto out = context.out();
-    auto&& it = fmt::internal::reserve(out, size);
+    auto&& it = fmt::detail::reserve(out, size);
     it = std::copy_n(begin, size, it);
     context.advance_to(out);
   }
 
-  void on_arg_id() {
-    arg = context.arg(parse_ctx.next_arg_id());
-  }
-  void on_arg_id(unsigned id) {
-    parse_ctx.check_arg_id(id);
-    arg = context.arg(id);
-  }
-  void on_arg_id(fmt::basic_string_view<Char>) {}
+  int on_arg_id() { return parse_ctx.next_arg_id(); }
+  int on_arg_id(unsigned id) { return parse_ctx.check_arg_id(id), id; }
+  int on_arg_id(fmt::basic_string_view<Char>) { return 0; }
 
-  void on_replacement_field(const Char* p) {
-    parse_ctx.advance_to(parse_ctx.begin() + (p - &*parse_ctx.begin()));
+  void on_replacement_field(int id, const Char* p) {
+    auto arg = context.arg(id);
+    parse_ctx.advance_to(parse_ctx.begin() + (p  - &*parse_ctx.begin()));
     custom_formatter<Context> f(parse_ctx, context);
     if (!visit_format_arg(f, arg))
       context.advance_to(visit_format_arg(ArgFormatter(context, &parse_ctx), arg));
   }
 
-  const Char* on_format_specs(const Char* begin, const Char* end) {
+  const Char* on_format_specs(int id, const Char* begin, const Char* end) {
+    auto arg = context.arg(id);
     parse_ctx.advance_to(parse_ctx.begin() + (begin - &*parse_ctx.begin()));
     custom_formatter<Context> f(parse_ctx, context);
     if (visit_format_arg(f, arg)) return &*parse_ctx.begin();
     fmt::basic_format_specs<Char> specs;
-    using fmt::internal::specs_handler;
+    using fmt::detail::specs_handler;
     using parse_context = basic_format_parse_context<Char>;
-    fmt::internal::specs_checker<specs_handler<parse_context, Context>> handler(
+    fmt::detail::specs_checker<specs_handler<parse_context, Context>> handler(
         specs_handler<parse_context, Context>(specs, parse_ctx, context), get_type(arg));
     begin = parse_format_specs(begin, end, handler);
     if (begin == end || *begin != '}') on_error("missing '}' in format string");
@@ -631,7 +627,6 @@ struct format_handler : detail::error_handler {
 
   basic_format_parse_context<Char> parse_ctx;
   Context context;
-  basic_format_arg<Context> arg;
 };
 
 template <typename T, typename Char>
@@ -640,46 +635,45 @@ struct formatter {
   // terminating '}'.
   template <typename ParseContext>
   FMT_CONSTEXPR typename ParseContext::iterator parse(ParseContext& ctx) {
-    namespace internal = fmt::internal;
-    typedef internal::dynamic_specs_handler<ParseContext> handler_type;
-    auto type = internal::mapped_type_constant<T, fmt::buffer_context<Char>>::value;
-    internal::specs_checker<handler_type> handler(handler_type(specs_, ctx),
+    namespace detail = fmt::detail;
+    typedef detail::dynamic_specs_handler<ParseContext> handler_type;
+    auto type = detail::mapped_type_constant<T, fmt::buffer_context<Char>>::value;
+    detail::specs_checker<handler_type> handler(handler_type(specs_, ctx),
                                                   type);
     auto it = parse_format_specs(ctx.begin(), ctx.end(), handler);
     auto type_spec = specs_.type;
     auto eh = ctx.error_handler();
     switch (type) {
-    case internal::type::none_type:
-    case internal::type::named_arg_type:
+    case detail::type::none_type:
       FMT_ASSERT(false, "invalid argument type");
       break;
-    case internal::type::int_type:
-    case internal::type::uint_type:
-    case internal::type::long_long_type:
-    case internal::type::ulong_long_type:
-    case internal::type::bool_type:
+    case detail::type::int_type:
+    case detail::type::uint_type:
+    case detail::type::long_long_type:
+    case detail::type::ulong_long_type:
+    case detail::type::bool_type:
       handle_int_type_spec(type_spec,
-                           internal::int_type_checker<decltype(eh)>(eh));
+                           detail::int_type_checker<decltype(eh)>(eh));
       break;
-    case internal::type::char_type:
+    case detail::type::char_type:
       handle_char_specs(
-          &specs_, internal::char_specs_checker<decltype(eh)>(type_spec, eh));
+          &specs_, detail::char_specs_checker<decltype(eh)>(type_spec, eh));
       break;
-    case internal::type::double_type:
-    case internal::type::long_double_type:
-      internal::parse_float_type_spec(specs_, eh);
+    case detail::type::double_type:
+    case detail::type::long_double_type:
+      detail::parse_float_type_spec(specs_, eh);
       break;
-    case internal::type::cstring_type:
-      internal::handle_cstring_type_spec(
-          type_spec, internal::cstring_type_checker<decltype(eh)>(eh));
+    case detail::type::cstring_type:
+      detail::handle_cstring_type_spec(
+          type_spec, detail::cstring_type_checker<decltype(eh)>(eh));
       break;
-    case internal::type::string_type:
-      internal::check_string_type_spec(type_spec, eh);
+    case detail::type::string_type:
+      detail::check_string_type_spec(type_spec, eh);
       break;
-    case internal::type::pointer_type:
-      internal::check_pointer_type_spec(type_spec, eh);
+    case detail::type::pointer_type:
+      detail::check_pointer_type_spec(type_spec, eh);
       break;
-    case internal::type::custom_type:
+    case detail::type::custom_type:
       // Custom format specifiers should be checked in parse functions of
       // formatter specializations.
       break;
@@ -689,18 +683,18 @@ struct formatter {
 
   template <typename FormatContext>
   auto format(const T& val, FormatContext& ctx) -> decltype(ctx.out()) {
-    fmt::internal::handle_dynamic_spec<fmt::internal::width_checker>(
+    fmt::detail::handle_dynamic_spec<fmt::detail::width_checker>(
         specs_.width, specs_.width_ref, ctx);
-    fmt::internal::handle_dynamic_spec<fmt::internal::precision_checker>(
+    fmt::detail::handle_dynamic_spec<fmt::detail::precision_checker>(
         specs_.precision, specs_.precision_ref, ctx);
-    using range_type = fmt::internal::output_range<typename FormatContext::iterator,
-                         typename FormatContext::char_type>;
-    return visit_format_arg(arg_formatter<range_type>(ctx, nullptr, &specs_),
+    using af = arg_formatter<typename FormatContext::iterator,
+                             typename FormatContext::char_type>;
+    return visit_format_arg(af(ctx, nullptr, &specs_),
                             basic_format_arg<FormatContext>(val));
   }
 
  private:
-  fmt::internal::dynamic_format_specs<Char> specs_;
+  fmt::detail::dynamic_format_specs<Char> specs_;
 };
 }  // namespace detail
 
@@ -717,11 +711,11 @@ template<class... Args>
 
 string vformat(string_view fmt, format_args args) {
   fmt::memory_buffer mbuf;
-  fmt::internal::buffer<char>& buf = mbuf;
-  using range = fmt::buffer_range<char>;
-  detail::format_handler<detail::arg_formatter<range>, char, format_context>
-    h(range(std::back_inserter(buf)), fmt, args, {});
-  fmt::internal::parse_format_string<false>(fmt::to_string_view(fmt), h);
+  fmt::detail::buffer<char>& buf = mbuf;
+  using af = detail::arg_formatter<fmt::format_context::iterator, char>;
+  detail::format_handler<af, char, format_context>
+    h(std::back_inserter(buf), fmt, args, {});
+  fmt::detail::parse_format_string<false>(fmt::to_string_view(fmt), h);
   return to_string(mbuf);
 }
 
@@ -741,10 +735,10 @@ template<class Out, class... Args>
 
 template<class Out>
   Out vformat_to(Out out, string_view fmt, format_args_t<fmt::type_identity_t<Out>, char> args) {
-    using range = fmt::internal::output_range<Out, char>;
-    detail::format_handler<detail::arg_formatter<range>, char, basic_format_context<Out, char>>
-      h(range(out), fmt, args, {});
-    fmt::internal::parse_format_string<false>(fmt::to_string_view(fmt), h);
+    using af = detail::arg_formatter<Out, char>;
+    detail::format_handler<af, char, basic_format_context<Out, char>>
+      h(out, fmt, args, {});
+    fmt::detail::parse_format_string<false>(fmt::to_string_view(fmt), h);
     return h.context.out();
   }
 
diff --git a/test/format-impl-test.cc b/test/format-impl-test.cc
index 21e91014..10e7a7ae 100644
--- a/test/format-impl-test.cc
+++ b/test/format-impl-test.cc
@@ -21,9 +21,9 @@
 
 #undef max
 
-using fmt::internal::bigint;
-using fmt::internal::fp;
-using fmt::internal::max_value;
+using fmt::detail::bigint;
+using fmt::detail::fp;
+using fmt::detail::max_value;
 
 static_assert(!std::is_copy_constructible<bigint>::value, "");
 static_assert(!std::is_copy_assignable<bigint>::value, "");
@@ -102,7 +102,7 @@ TEST(BigIntTest, Multiply) {
 }
 
 TEST(BigIntTest, Accumulator) {
-  fmt::internal::accumulator acc;
+  fmt::detail::accumulator acc;
   EXPECT_EQ(acc.lower, 0);
   EXPECT_EQ(acc.upper, 0);
   acc.upper = 12;
@@ -110,7 +110,7 @@ TEST(BigIntTest, Accumulator) {
   EXPECT_EQ(static_cast<uint32_t>(acc), 34);
   acc += 56;
   EXPECT_EQ(acc.lower, 90);
-  acc += fmt::internal::max_value<uint64_t>();
+  acc += fmt::detail::max_value<uint64_t>();
   EXPECT_EQ(acc.upper, 13);
   EXPECT_EQ(acc.lower, 89);
   acc >>= 32;
@@ -262,7 +262,7 @@ TEST(FPTest, GetCachedPower) {
   typedef std::numeric_limits<double> limits;
   for (auto exp = limits::min_exponent; exp <= limits::max_exponent; ++exp) {
     int dec_exp = 0;
-    auto fp = fmt::internal::get_cached_power(exp, dec_exp);
+    auto fp = fmt::detail::get_cached_power(exp, dec_exp);
     EXPECT_LE(exp, fp.e);
     int dec_exp_step = 8;
     EXPECT_LE(fp.e, exp + dec_exp_step * log2(10));
@@ -271,8 +271,8 @@ TEST(FPTest, GetCachedPower) {
 }
 
 TEST(FPTest, GetRoundDirection) {
-  using fmt::internal::get_round_direction;
-  using fmt::internal::round_direction;
+  using fmt::detail::get_round_direction;
+  using fmt::detail::round_direction;
   EXPECT_EQ(round_direction::down, get_round_direction(100, 50, 0));
   EXPECT_EQ(round_direction::up, get_round_direction(100, 51, 0));
   EXPECT_EQ(round_direction::down, get_round_direction(100, 40, 10));
@@ -295,9 +295,9 @@ TEST(FPTest, GetRoundDirection) {
 }
 
 TEST(FPTest, FixedHandler) {
-  struct handler : fmt::internal::fixed_handler {
+  struct handler : fmt::detail::fixed_handler {
     char buffer[10];
-    handler(int prec = 0) : fmt::internal::fixed_handler() {
+    handler(int prec = 0) : fmt::detail::fixed_handler() {
       buf = buffer;
       precision = prec;
     }
@@ -306,7 +306,7 @@ TEST(FPTest, FixedHandler) {
   handler().on_digit('0', 100, 99, 0, exp, false);
   EXPECT_THROW(handler().on_digit('0', 100, 100, 0, exp, false),
                assertion_failure);
-  namespace digits = fmt::internal::digits;
+  namespace digits = fmt::detail::digits;
   EXPECT_EQ(handler(1).on_digit('0', 100, 10, 10, exp, false), digits::done);
   // Check that divisor - error doesn't overflow.
   EXPECT_EQ(handler(1).on_digit('0', 100, 10, 101, exp, false), digits::error);
@@ -318,7 +318,7 @@ TEST(FPTest, FixedHandler) {
 
 TEST(FPTest, GrisuFormatCompilesWithNonIEEEDouble) {
   fmt::memory_buffer buf;
-  format_float(0.42, -1, fmt::internal::float_specs(), buf);
+  format_float(0.42, -1, fmt::detail::float_specs(), buf);
 }
 
 template <typename T> struct value_extractor {
@@ -330,11 +330,11 @@ template <typename T> struct value_extractor {
 
 #if FMT_USE_INT128
   // Apple Clang does not define typeid for __int128_t and __uint128_t.
-  FMT_NORETURN T operator()(fmt::internal::int128_t) {
+  FMT_NORETURN T operator()(fmt::detail::int128_t) {
     throw std::runtime_error("invalid type __int128_t");
   }
 
-  FMT_NORETURN T operator()(fmt::internal::uint128_t) {
+  FMT_NORETURN T operator()(fmt::detail::uint128_t) {
     throw std::runtime_error("invalid type __uint128_t");
   }
 #endif
@@ -342,9 +342,9 @@ template <typename T> struct value_extractor {
 
 TEST(FormatTest, ArgConverter) {
   long long value = max_value<long long>();
-  auto arg = fmt::internal::make_arg<fmt::format_context>(value);
+  auto arg = fmt::detail::make_arg<fmt::format_context>(value);
   fmt::visit_format_arg(
-      fmt::internal::arg_converter<long long, fmt::format_context>(arg, 'd'),
+      fmt::detail::arg_converter<long long, fmt::format_context>(arg, 'd'),
       arg);
   EXPECT_EQ(value, fmt::visit_format_arg(value_extractor<long long>(), arg));
 }
@@ -360,9 +360,9 @@ TEST(FormatTest, FormatNegativeNaN) {
 TEST(FormatTest, StrError) {
   char* message = nullptr;
   char buffer[BUFFER_SIZE];
-  EXPECT_ASSERT(fmt::internal::safe_strerror(EDOM, message = nullptr, 0),
+  EXPECT_ASSERT(fmt::detail::safe_strerror(EDOM, message = nullptr, 0),
                 "invalid buffer");
-  EXPECT_ASSERT(fmt::internal::safe_strerror(EDOM, message = buffer, 0),
+  EXPECT_ASSERT(fmt::detail::safe_strerror(EDOM, message = buffer, 0),
                 "invalid buffer");
   buffer[0] = 'x';
 #if defined(_GNU_SOURCE) && !defined(__COVERITY__)
@@ -374,18 +374,18 @@ TEST(FormatTest, StrError) {
 #endif
 
   int result =
-      fmt::internal::safe_strerror(error_code, message = buffer, BUFFER_SIZE);
+      fmt::detail::safe_strerror(error_code, message = buffer, BUFFER_SIZE);
   EXPECT_EQ(result, 0);
-  std::size_t message_size = std::strlen(message);
+  size_t message_size = std::strlen(message);
   EXPECT_GE(BUFFER_SIZE - 1u, message_size);
   EXPECT_EQ(get_system_error(error_code), message);
 
   // safe_strerror never uses buffer on MinGW.
 #if !defined(__MINGW32__) && !defined(__sun)
   result =
-      fmt::internal::safe_strerror(error_code, message = buffer, message_size);
+      fmt::detail::safe_strerror(error_code, message = buffer, message_size);
   EXPECT_EQ(ERANGE, result);
-  result = fmt::internal::safe_strerror(error_code, message = buffer, 1);
+  result = fmt::detail::safe_strerror(error_code, message = buffer, 1);
   EXPECT_EQ(buffer, message);  // Message should point to buffer.
   EXPECT_EQ(ERANGE, result);
   EXPECT_STREQ("", message);
@@ -397,51 +397,48 @@ TEST(FormatTest, FormatErrorCode) {
   {
     fmt::memory_buffer buffer;
     format_to(buffer, "garbage");
-    fmt::internal::format_error_code(buffer, 42, "test");
+    fmt::detail::format_error_code(buffer, 42, "test");
     EXPECT_EQ("test: " + msg, to_string(buffer));
   }
   {
     fmt::memory_buffer buffer;
     std::string prefix(fmt::inline_buffer_size - msg.size() - sep.size() + 1,
                        'x');
-    fmt::internal::format_error_code(buffer, 42, prefix);
+    fmt::detail::format_error_code(buffer, 42, prefix);
     EXPECT_EQ(msg, to_string(buffer));
   }
   int codes[] = {42, -1};
-  for (std::size_t i = 0, n = sizeof(codes) / sizeof(*codes); i < n; ++i) {
+  for (size_t i = 0, n = sizeof(codes) / sizeof(*codes); i < n; ++i) {
     // Test maximum buffer size.
     msg = fmt::format("error {}", codes[i]);
     fmt::memory_buffer buffer;
     std::string prefix(fmt::inline_buffer_size - msg.size() - sep.size(), 'x');
-    fmt::internal::format_error_code(buffer, codes[i], prefix);
+    fmt::detail::format_error_code(buffer, codes[i], prefix);
     EXPECT_EQ(prefix + sep + msg, to_string(buffer));
-    std::size_t size = fmt::inline_buffer_size;
+    size_t size = fmt::inline_buffer_size;
     EXPECT_EQ(size, buffer.size());
     buffer.resize(0);
     // Test with a message that doesn't fit into the buffer.
     prefix += 'x';
-    fmt::internal::format_error_code(buffer, codes[i], prefix);
+    fmt::detail::format_error_code(buffer, codes[i], prefix);
     EXPECT_EQ(msg, to_string(buffer));
   }
 }
 
 TEST(FormatTest, CountCodePoints) {
-#ifndef __cpp_char8_t
-  using fmt::char8_t;
-#endif
-  EXPECT_EQ(
-      4, fmt::internal::count_code_points(
-             fmt::basic_string_view<fmt::internal::char8_type>(
-                 reinterpret_cast<const fmt::internal::char8_type*>("ёжик"))));
+  EXPECT_EQ(4,
+            fmt::detail::count_code_points(
+                fmt::basic_string_view<fmt::detail::char8_type>(
+                    reinterpret_cast<const fmt::detail::char8_type*>("ёжик"))));
 }
 
-// Tests fmt::internal::count_digits for integer type Int.
+// Tests fmt::detail::count_digits for integer type Int.
 template <typename Int> void test_count_digits() {
-  for (Int i = 0; i < 10; ++i) EXPECT_EQ(1u, fmt::internal::count_digits(i));
+  for (Int i = 0; i < 10; ++i) EXPECT_EQ(1u, fmt::detail::count_digits(i));
   for (Int i = 1, n = 1, end = max_value<Int>() / 10; n <= end; ++i) {
     n *= 10;
-    EXPECT_EQ(i, fmt::internal::count_digits(n - 1));
-    EXPECT_EQ(i + 1, fmt::internal::count_digits(n));
+    EXPECT_EQ(i, fmt::detail::count_digits(n - 1));
+    EXPECT_EQ(i + 1, fmt::detail::count_digits(n));
   }
 }
 
@@ -450,11 +447,10 @@ TEST(UtilTest, CountDigits) {
   test_count_digits<uint64_t>();
 }
 
-TEST(UtilTest, WriteUIntPtr) {
-  fmt::memory_buffer buf;
-  fmt::internal::writer writer(buf);
-  writer.write_pointer(
-      fmt::internal::fallback_uintptr(reinterpret_cast<void*>(0xface)),
-      nullptr);
-  EXPECT_EQ("0xface", to_string(buf));
+TEST(UtilTest, WriteFallbackUIntPtr) {
+  std::string s;
+  fmt::detail::write_ptr<char>(
+      std::back_inserter(s),
+      fmt::detail::fallback_uintptr(reinterpret_cast<void*>(0xface)), nullptr);
+  EXPECT_EQ(s, "0xface");
 }
diff --git a/test/format-test.cc b/test/format-test.cc
index e9304cee..2a25566c 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -35,10 +35,6 @@
 #include "util.h"
 
 #undef ERROR
-#undef min
-#undef max
-
-using std::size_t;
 
 using fmt::basic_memory_buffer;
 using fmt::format;
@@ -47,8 +43,7 @@ using fmt::memory_buffer;
 using fmt::string_view;
 using fmt::wmemory_buffer;
 using fmt::wstring_view;
-using fmt::internal::basic_writer;
-using fmt::internal::max_value;
+using fmt::detail::max_value;
 
 using testing::Return;
 using testing::StrictMock;
@@ -102,47 +97,6 @@ void std_format(long double value, std::wstring& result) {
   result = buffer;
 }
 #endif
-
-// Checks if writing value to BasicWriter<Char> produces the same result
-// as writing it to std::basic_ostringstream<Char>.
-template <typename Char, typename T>
-::testing::AssertionResult check_write(const T& value, const char* type) {
-  fmt::basic_memory_buffer<Char> buffer;
-  using range = fmt::buffer_range<Char>;
-  basic_writer<range> writer(buffer);
-  writer.write(value);
-  std::basic_string<Char> actual = to_string(buffer);
-  std::basic_string<Char> expected;
-  std_format(value, expected);
-  if (expected == actual) return ::testing::AssertionSuccess();
-  return ::testing::AssertionFailure()
-         << "Value of: (Writer<" << type << ">() << value).str()\n"
-         << "  Actual: " << actual << "\n"
-         << "Expected: " << expected << "\n";
-}
-
-struct AnyWriteChecker {
-  template <typename T>
-  ::testing::AssertionResult operator()(const char*, const T& value) const {
-    ::testing::AssertionResult result = check_write<char>(value, "char");
-    return result ? check_write<wchar_t>(value, "wchar_t") : result;
-  }
-};
-
-template <typename Char> struct WriteChecker {
-  template <typename T>
-  ::testing::AssertionResult operator()(const char*, const T& value) const {
-    return check_write<Char>(value, "char");
-  }
-};
-
-// Checks if writing value to BasicWriter produces the same result
-// as writing it to std::ostringstream both for char and wchar_t.
-#define CHECK_WRITE(value) EXPECT_PRED_FORMAT1(AnyWriteChecker(), value)
-
-#define CHECK_WRITE_CHAR(value) EXPECT_PRED_FORMAT1(WriteChecker<char>(), value)
-#define CHECK_WRITE_WCHAR(value) \
-  EXPECT_PRED_FORMAT1(WriteChecker<wchar_t>(), value)
 }  // namespace
 
 struct uint32_pair {
@@ -150,10 +104,10 @@ struct uint32_pair {
 };
 
 TEST(UtilTest, BitCast) {
-  auto s = fmt::internal::bit_cast<uint32_pair>(uint64_t{42});
-  EXPECT_EQ(fmt::internal::bit_cast<uint64_t>(s), 42ull);
-  s = fmt::internal::bit_cast<uint32_pair>(uint64_t(~0ull));
-  EXPECT_EQ(fmt::internal::bit_cast<uint64_t>(s), ~0ull);
+  auto s = fmt::detail::bit_cast<uint32_pair>(uint64_t{42});
+  EXPECT_EQ(fmt::detail::bit_cast<uint64_t>(s), 42ull);
+  s = fmt::detail::bit_cast<uint32_pair>(uint64_t(~0ull));
+  EXPECT_EQ(fmt::detail::bit_cast<uint64_t>(s), ~0ull);
 }
 
 TEST(UtilTest, Increment) {
@@ -178,18 +132,18 @@ TEST(UtilTest, ParseNonnegativeInt) {
   fmt::string_view s = "10000000000";
   auto begin = s.begin(), end = s.end();
   EXPECT_THROW_MSG(
-      parse_nonnegative_int(begin, end, fmt::internal::error_handler()),
+      parse_nonnegative_int(begin, end, fmt::detail::error_handler()),
       fmt::format_error, "number is too big");
   s = "2147483649";
   begin = s.begin();
   end = s.end();
   EXPECT_THROW_MSG(
-      parse_nonnegative_int(begin, end, fmt::internal::error_handler()),
+      parse_nonnegative_int(begin, end, fmt::detail::error_handler()),
       fmt::format_error, "number is too big");
 }
 
 TEST(IteratorTest, CountingIterator) {
-  fmt::internal::counting_iterator it;
+  fmt::detail::counting_iterator it;
   auto prev = it++;
   EXPECT_EQ(prev.count(), 0);
   EXPECT_EQ(it.count(), 1);
@@ -197,7 +151,7 @@ TEST(IteratorTest, CountingIterator) {
 
 TEST(IteratorTest, TruncatingIterator) {
   char* p = nullptr;
-  fmt::internal::truncating_iterator<char*> it(p, 3);
+  fmt::detail::truncating_iterator<char*> it(p, 3);
   auto prev = it++;
   EXPECT_EQ(prev.base(), p);
   EXPECT_EQ(it.base(), p + 1);
@@ -206,7 +160,7 @@ TEST(IteratorTest, TruncatingIterator) {
 TEST(IteratorTest, TruncatingBackInserter) {
   std::string buffer;
   auto bi = std::back_inserter(buffer);
-  fmt::internal::truncating_iterator<decltype(bi)> it(bi, 2);
+  fmt::detail::truncating_iterator<decltype(bi)> it(bi, 2);
   *it++ = '4';
   *it++ = '2';
   *it++ = '1';
@@ -215,20 +169,20 @@ TEST(IteratorTest, TruncatingBackInserter) {
 }
 
 TEST(IteratorTest, IsOutputIterator) {
-  EXPECT_TRUE(fmt::internal::is_output_iterator<char*>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<const char*>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<std::string>::value);
-  EXPECT_TRUE(fmt::internal::is_output_iterator<
+  EXPECT_TRUE(fmt::detail::is_output_iterator<char*>::value);
+  EXPECT_FALSE(fmt::detail::is_output_iterator<const char*>::value);
+  EXPECT_FALSE(fmt::detail::is_output_iterator<std::string>::value);
+  EXPECT_TRUE(fmt::detail::is_output_iterator<
               std::back_insert_iterator<std::string>>::value);
-  EXPECT_TRUE(fmt::internal::is_output_iterator<std::string::iterator>::value);
+  EXPECT_TRUE(fmt::detail::is_output_iterator<std::string::iterator>::value);
   EXPECT_FALSE(
-      fmt::internal::is_output_iterator<std::string::const_iterator>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<std::list<char>>::value);
+      fmt::detail::is_output_iterator<std::string::const_iterator>::value);
+  EXPECT_FALSE(fmt::detail::is_output_iterator<std::list<char>>::value);
   EXPECT_TRUE(
-      fmt::internal::is_output_iterator<std::list<char>::iterator>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<
-               std::list<char>::const_iterator>::value);
-  EXPECT_FALSE(fmt::internal::is_output_iterator<uint32_pair>::value);
+      fmt::detail::is_output_iterator<std::list<char>::iterator>::value);
+  EXPECT_FALSE(
+      fmt::detail::is_output_iterator<std::list<char>::const_iterator>::value);
+  EXPECT_FALSE(fmt::detail::is_output_iterator<uint32_pair>::value);
 }
 
 TEST(MemoryBufferTest, Ctor) {
@@ -343,10 +297,10 @@ TEST(MemoryBufferTest, Grow) {
   mock_allocator<int> alloc;
   struct TestMemoryBuffer : Base {
     TestMemoryBuffer(Allocator alloc) : Base(alloc) {}
-    void grow(std::size_t size) { Base::grow(size); }
+    void grow(size_t size) { Base::grow(size); }
   } buffer((Allocator(&alloc)));
   buffer.resize(7);
-  using fmt::internal::to_unsigned;
+  using fmt::detail::to_unsigned;
   for (int i = 0; i < 7; ++i) buffer[to_unsigned(i)] = i * i;
   EXPECT_EQ(10u, buffer.capacity());
   int mem[20];
@@ -371,7 +325,7 @@ TEST(MemoryBufferTest, Allocator) {
     basic_memory_buffer<char, 10, TestAllocator> buffer2(
         (TestAllocator(&alloc)));
     EXPECT_EQ(&alloc, buffer2.get_allocator().get());
-    std::size_t size = 2 * fmt::inline_buffer_size;
+    size_t size = 2 * fmt::inline_buffer_size;
     EXPECT_CALL(alloc, allocate(size)).WillOnce(Return(&mem));
     buffer2.reserve(size);
     EXPECT_CALL(alloc, deallocate(&mem, size));
@@ -382,7 +336,7 @@ TEST(MemoryBufferTest, ExceptionInDeallocate) {
   typedef allocator_ref<mock_allocator<char>> TestAllocator;
   StrictMock<mock_allocator<char>> alloc;
   basic_memory_buffer<char, 10, TestAllocator> buffer((TestAllocator(&alloc)));
-  std::size_t size = 2 * fmt::inline_buffer_size;
+  size_t size = 2 * fmt::inline_buffer_size;
   std::vector<char> mem(size);
   {
     EXPECT_CALL(alloc, allocate(size)).WillOnce(Return(&mem[0]));
@@ -397,27 +351,27 @@ TEST(MemoryBufferTest, ExceptionInDeallocate) {
     EXPECT_THROW(buffer.reserve(2 * size), std::exception);
     EXPECT_EQ(&mem2[0], &buffer[0]);
     // Check that the data has been copied.
-    for (std::size_t i = 0; i < size; ++i) EXPECT_EQ('x', buffer[i]);
+    for (size_t i = 0; i < size; ++i) EXPECT_EQ('x', buffer[i]);
   }
   EXPECT_CALL(alloc, deallocate(&mem2[0], 2 * size));
 }
 
 TEST(UtilTest, UTF8ToUTF16) {
-  fmt::internal::utf8_to_utf16 u("лошадка");
+  fmt::detail::utf8_to_utf16 u("лошадка");
   EXPECT_EQ(L"\x043B\x043E\x0448\x0430\x0434\x043A\x0430", u.str());
   EXPECT_EQ(7, u.size());
   // U+10437 { DESERET SMALL LETTER YEE }
-  EXPECT_EQ(L"\xD801\xDC37", fmt::internal::utf8_to_utf16("𐐷").str());
-  EXPECT_THROW_MSG(fmt::internal::utf8_to_utf16("\xc3\x28"), std::runtime_error,
+  EXPECT_EQ(L"\xD801\xDC37", fmt::detail::utf8_to_utf16("𐐷").str());
+  EXPECT_THROW_MSG(fmt::detail::utf8_to_utf16("\xc3\x28"), std::runtime_error,
                    "invalid utf8");
-  EXPECT_THROW_MSG(fmt::internal::utf8_to_utf16(fmt::string_view("л", 1)),
+  EXPECT_THROW_MSG(fmt::detail::utf8_to_utf16(fmt::string_view("л", 1)),
                    std::runtime_error, "invalid utf8");
-  EXPECT_EQ(L"123456", fmt::internal::utf8_to_utf16("123456").str());
+  EXPECT_EQ(L"123456", fmt::detail::utf8_to_utf16("123456").str());
 }
 
 TEST(UtilTest, UTF8ToUTF16EmptyString) {
   std::string s = "";
-  fmt::internal::utf8_to_utf16 u(s.c_str());
+  fmt::detail::utf8_to_utf16 u(s.c_str());
   EXPECT_EQ(L"", u.str());
   EXPECT_EQ(s.size(), u.size());
 }
@@ -479,101 +433,6 @@ TEST(StringViewTest, Ctor) {
   EXPECT_EQ(4u, string_view(std::string("defg")).size());
 }
 
-TEST(WriterTest, Data) {
-  memory_buffer buf;
-  fmt::internal::writer w(buf);
-  w.write(42);
-  EXPECT_EQ("42", to_string(buf));
-}
-
-TEST(WriterTest, WriteInt) {
-  CHECK_WRITE(42);
-  CHECK_WRITE(-42);
-  CHECK_WRITE(static_cast<short>(12));
-  CHECK_WRITE(34u);
-  CHECK_WRITE(std::numeric_limits<int>::min());
-  CHECK_WRITE(max_value<int>());
-  CHECK_WRITE(max_value<unsigned>());
-}
-
-TEST(WriterTest, WriteLong) {
-  CHECK_WRITE(56l);
-  CHECK_WRITE(78ul);
-  CHECK_WRITE(std::numeric_limits<long>::min());
-  CHECK_WRITE(max_value<long>());
-  CHECK_WRITE(max_value<unsigned long>());
-}
-
-TEST(WriterTest, WriteLongLong) {
-  CHECK_WRITE(56ll);
-  CHECK_WRITE(78ull);
-  CHECK_WRITE(std::numeric_limits<long long>::min());
-  CHECK_WRITE(max_value<long long>());
-  CHECK_WRITE(max_value<unsigned long long>());
-}
-
-TEST(WriterTest, WriteDouble) {
-  CHECK_WRITE(4.2);
-  CHECK_WRITE(-4.2);
-  auto min = std::numeric_limits<double>::min();
-  auto max = max_value<double>();
-  if (fmt::internal::use_grisu<double>()) {
-    EXPECT_EQ("2.2250738585072014e-308", fmt::format("{}", min));
-    EXPECT_EQ("1.7976931348623157e+308", fmt::format("{}", max));
-  } else {
-    CHECK_WRITE(min);
-    CHECK_WRITE(max);
-  }
-}
-
-TEST(WriterTest, WriteLongDouble) {
-  CHECK_WRITE(4.2l);
-  CHECK_WRITE_CHAR(-4.2l);
-  std::wstring str;
-  std_format(4.2l, str);
-  if (str[0] != '-')
-    CHECK_WRITE_WCHAR(-4.2l);
-  else
-    fmt::print("warning: long double formatting with std::swprintf is broken");
-  auto min = std::numeric_limits<long double>::min();
-  auto max = max_value<long double>();
-  if (fmt::internal::use_grisu<long double>()) {
-    EXPECT_EQ("2.2250738585072014e-308", fmt::format("{}", min));
-    EXPECT_EQ("1.7976931348623157e+308", fmt::format("{}", max));
-  } else {
-    CHECK_WRITE(min);
-    CHECK_WRITE(max);
-  }
-}
-
-TEST(WriterTest, WriteDoubleAtBufferBoundary) {
-  memory_buffer buf;
-  fmt::internal::writer writer(buf);
-  for (int i = 0; i < 100; ++i) writer.write(1.23456789);
-}
-
-TEST(WriterTest, WriteDoubleWithFilledBuffer) {
-  memory_buffer buf;
-  fmt::internal::writer writer(buf);
-  // Fill the buffer.
-  for (int i = 0; i < fmt::inline_buffer_size; ++i) writer.write(' ');
-  writer.write(1.2);
-  fmt::string_view sv(buf.data(), buf.size());
-  sv.remove_prefix(fmt::inline_buffer_size);
-  EXPECT_EQ("1.2", sv);
-}
-
-TEST(WriterTest, WriteChar) { CHECK_WRITE('a'); }
-
-TEST(WriterTest, WriteWideChar) { CHECK_WRITE_WCHAR(L'a'); }
-
-TEST(WriterTest, WriteString) {
-  CHECK_WRITE_CHAR("abc");
-  CHECK_WRITE_WCHAR("abc");
-}
-
-TEST(WriterTest, WriteWideString) { CHECK_WRITE_WCHAR(L"abc"); }
-
 TEST(FormatToTest, FormatWithoutArgs) {
   std::string s;
   fmt::format_to(std::back_inserter(s), "test");
@@ -640,15 +499,14 @@ TEST(FormatterTest, ArgErrors) {
   EXPECT_THROW_MSG(format("{"), format_error, "invalid format string");
   EXPECT_THROW_MSG(format("{?}"), format_error, "invalid format string");
   EXPECT_THROW_MSG(format("{0"), format_error, "invalid format string");
-  EXPECT_THROW_MSG(format("{0}"), format_error, "argument index out of range");
+  EXPECT_THROW_MSG(format("{0}"), format_error, "argument not found");
   EXPECT_THROW_MSG(format("{00}", 42), format_error, "invalid format string");
 
   char format_str[BUFFER_SIZE];
   safe_sprintf(format_str, "{%u", INT_MAX);
   EXPECT_THROW_MSG(format(format_str), format_error, "invalid format string");
   safe_sprintf(format_str, "{%u}", INT_MAX);
-  EXPECT_THROW_MSG(format(format_str), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(format(format_str), format_error, "argument not found");
 
   safe_sprintf(format_str, "{%u", INT_MAX + 1u);
   EXPECT_THROW_MSG(format(format_str), format_error, "number is too big");
@@ -673,19 +531,18 @@ template <> struct TestFormat<0> {
 TEST(FormatterTest, ManyArgs) {
   EXPECT_EQ("19", TestFormat<20>::format("{19}"));
   EXPECT_THROW_MSG(TestFormat<20>::format("{20}"), format_error,
-                   "argument index out of range");
+                   "argument not found");
   EXPECT_THROW_MSG(TestFormat<21>::format("{21}"), format_error,
-                   "argument index out of range");
-  enum { max_packed_args = fmt::internal::max_packed_args };
+                   "argument not found");
+  enum { max_packed_args = fmt::detail::max_packed_args };
   std::string format_str = fmt::format("{{{}}}", max_packed_args + 1);
   EXPECT_THROW_MSG(TestFormat<max_packed_args>::format(format_str),
-                   format_error, "argument index out of range");
+                   format_error, "argument not found");
 }
 
 TEST(FormatterTest, NamedArg) {
   EXPECT_EQ("1/a/A", format("{_1}/{a_}/{A_}", fmt::arg("a_", 'a'),
                             fmt::arg("A_", "A"), fmt::arg("_1", 1)));
-  EXPECT_THROW_MSG(format("{a}"), format_error, "argument not found");
   EXPECT_EQ(" -42", format("{0:{width}}", -42, fmt::arg("width", 4)));
   EXPECT_EQ("st", format("{0:.{precision}}", "str", fmt::arg("precision", 2)));
   EXPECT_EQ("1 2", format("{} {two}", 1, fmt::arg("two", 2)));
@@ -695,6 +552,8 @@ TEST(FormatterTest, NamedArg) {
                          fmt::arg("i", 0), fmt::arg("j", 0), fmt::arg("k", 0),
                          fmt::arg("l", 0), fmt::arg("m", 0), fmt::arg("n", 0),
                          fmt::arg("o", 0), fmt::arg("p", 0)));
+  EXPECT_THROW_MSG(format("{a}"), format_error, "argument not found");
+  EXPECT_THROW_MSG(format("{a}", 42), format_error, "argument not found");
 }
 
 TEST(FormatterTest, AutoArgIndex) {
@@ -708,7 +567,7 @@ TEST(FormatterTest, AutoArgIndex) {
                    "cannot switch from manual to automatic argument indexing");
   EXPECT_THROW_MSG(format("{:.{0}}", 1.2345, 2), format_error,
                    "cannot switch from automatic to manual argument indexing");
-  EXPECT_THROW_MSG(format("{}"), format_error, "argument index out of range");
+  EXPECT_THROW_MSG(format("{}"), format_error, "argument not found");
 }
 
 TEST(FormatterTest, EmptySpecs) { EXPECT_EQ("42", format("{0:}", 42)); }
@@ -747,38 +606,8 @@ TEST(FormatterTest, RightAlign) {
   EXPECT_EQ("  0xface", format("{0:>8}", reinterpret_cast<void*>(0xface)));
 }
 
-#if FMT_NUMERIC_ALIGN
-TEST(FormatterTest, NumericAlign) {
-  EXPECT_EQ("  42", format("{0:=4}", 42));
-  EXPECT_EQ("+ 42", format("{0:=+4}", 42));
-  EXPECT_EQ("  42", format("{0:=4o}", 042));
-  EXPECT_EQ("+ 42", format("{0:=+4o}", 042));
-  EXPECT_EQ("  42", format("{0:=4x}", 0x42));
-  EXPECT_EQ("+ 42", format("{0:=+4x}", 0x42));
-  EXPECT_EQ("-  42", format("{0:=5}", -42));
-  EXPECT_EQ("   42", format("{0:=5}", 42u));
-  EXPECT_EQ("-  42", format("{0:=5}", -42l));
-  EXPECT_EQ("   42", format("{0:=5}", 42ul));
-  EXPECT_EQ("-  42", format("{0:=5}", -42ll));
-  EXPECT_EQ("   42", format("{0:=5}", 42ull));
-  EXPECT_EQ("-  42.0", format("{0:=7}", -42.0));
-  EXPECT_EQ("-  42.0", format("{0:=7}", -42.0l));
-  EXPECT_THROW_MSG(format("{0:=5", 'c'), format_error,
-                   "missing '}' in format string");
-  EXPECT_THROW_MSG(format("{0:=5}", 'c'), format_error,
-                   "invalid format specifier for char");
-  EXPECT_THROW_MSG(format("{0:=5}", "abc"), format_error,
-                   "format specifier requires numeric argument");
-  EXPECT_THROW_MSG(format("{0:=8}", reinterpret_cast<void*>(0xface)),
-                   format_error, "format specifier requires numeric argument");
-  EXPECT_EQ(" 1.0", fmt::format("{:= }", 1.0));
-}
-
-TEST(FormatToTest, FormatToNonbackInsertIteratorWithSignAndNumericAlignment) {
-  char buffer[16] = {};
-  fmt::format_to(fmt::internal::make_checked(buffer, 16), "{: =+}", 42.0);
-  EXPECT_STREQ("+42.0", buffer);
-}
+#if FMT_DEPRECATED_NUMERIC_ALIGN
+TEST(FormatterTest, NumericAlign) { EXPECT_EQ("0042", format("{0:=4}", 42)); }
 #endif
 
 TEST(FormatterTest, CenterAlign) {
@@ -969,7 +798,7 @@ TEST(FormatterTest, Width) {
   safe_sprintf(format_str, "{0:%u", UINT_MAX);
   increment(format_str + 3);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -999,7 +828,7 @@ TEST(FormatterTest, RuntimeWidth) {
   safe_sprintf(format_str, "{0:{%u", UINT_MAX);
   increment(format_str + 4);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -1011,8 +840,7 @@ TEST(FormatterTest, RuntimeWidth) {
   EXPECT_THROW_MSG(format("{0:{}", 0), format_error,
                    "cannot switch from manual to automatic argument indexing");
   EXPECT_THROW_MSG(format("{0:{?}}", 0), format_error, "invalid format string");
-  EXPECT_THROW_MSG(format("{0:{1}}", 0), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(format("{0:{1}}", 0), format_error, "argument not found");
 
   EXPECT_THROW_MSG(format("{0:{0:}}", 0), format_error,
                    "invalid format string");
@@ -1053,7 +881,7 @@ TEST(FormatterTest, Precision) {
   safe_sprintf(format_str, "{0:.%u", UINT_MAX);
   increment(format_str + 4);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -1134,7 +962,7 @@ TEST(FormatterTest, Precision) {
   EXPECT_THROW_MSG(format("{0:.2f}", reinterpret_cast<void*>(0xcafe)),
                    format_error,
                    "precision not allowed for this argument type");
-  EXPECT_THROW_MSG(format("{:.{}e}", 42.0, fmt::internal::max_value<int>()),
+  EXPECT_THROW_MSG(format("{:.{}e}", 42.0, fmt::detail::max_value<int>()),
                    format_error, "number is too big");
 
   EXPECT_EQ("st", format("{0:.2}", "str"));
@@ -1145,7 +973,7 @@ TEST(FormatterTest, RuntimePrecision) {
   safe_sprintf(format_str, "{0:.{%u", UINT_MAX);
   increment(format_str + 5);
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
-  std::size_t size = std::strlen(format_str);
+  size_t size = std::strlen(format_str);
   format_str[size] = '}';
   format_str[size + 1] = 0;
   EXPECT_THROW_MSG(format(format_str, 0), format_error, "number is too big");
@@ -1160,8 +988,7 @@ TEST(FormatterTest, RuntimePrecision) {
                    "invalid format string");
   EXPECT_THROW_MSG(format("{0:.{1}", 0, 0), format_error,
                    "precision not allowed for this argument type");
-  EXPECT_THROW_MSG(format("{0:.{1}}", 0), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(format("{0:.{1}}", 0), format_error, "argument not found");
 
   EXPECT_THROW_MSG(format("{0:.{0:}}", 0), format_error,
                    "invalid format string");
@@ -1256,7 +1083,8 @@ TEST(FormatterTest, FormatShort) {
 TEST(FormatterTest, FormatInt) {
   EXPECT_THROW_MSG(format("{0:v", 42), format_error,
                    "missing '}' in format string");
-  check_unknown_types(42, "bBdoxXnL", "integer");
+  check_unknown_types(42, "bBdoxXnLc", "integer");
+  EXPECT_EQ("x", format("{:c}", static_cast<int>('x')));
 }
 
 TEST(FormatterTest, FormatBin) {
@@ -1396,7 +1224,6 @@ TEST(FormatterTest, FormatOct) {
 }
 
 TEST(FormatterTest, FormatIntLocale) {
-  EXPECT_EQ("1234", format("{:n}", 1234));
   EXPECT_EQ("1234", format("{:L}", 1234));
 }
 
@@ -1413,7 +1240,7 @@ TEST(FormatterTest, FormatFloat) {
 }
 
 TEST(FormatterTest, FormatDouble) {
-  check_unknown_types(1.2, "eEfFgGaAn%", "double");
+  check_unknown_types(1.2, "eEfFgGaAnL%", "double");
   EXPECT_EQ("0.0", format("{:}", 0.0));
   EXPECT_EQ("0.000000", format("{:f}", 0.0));
   EXPECT_EQ("0", format("{:g}", 0.0));
@@ -1422,6 +1249,7 @@ TEST(FormatterTest, FormatDouble) {
   EXPECT_EQ("392.65", format("{:G}", 392.65));
   EXPECT_EQ("392.650000", format("{:f}", 392.65));
   EXPECT_EQ("392.650000", format("{:F}", 392.65));
+  EXPECT_EQ("42", format("{:L}", 42.0));
   char buffer[BUFFER_SIZE];
   safe_sprintf(buffer, "%e", 392.65);
   EXPECT_EQ(buffer, format("{0:e}", 392.65));
@@ -1492,7 +1320,7 @@ TEST(FormatterTest, FormatLongDouble) {
 }
 
 TEST(FormatterTest, FormatChar) {
-  const char types[] = "cbBdoxXnL";
+  const char types[] = "cbBdoxXL";
   check_unknown_types('a', types, "char");
   EXPECT_EQ("a", format("{0}", 'a'));
   EXPECT_EQ("z", format("{0:c}", 'z'));
@@ -1608,12 +1436,46 @@ TEST(FormatterTest, FormatExplicitlyConvertibleToStdStringView) {
 }
 #endif
 
+// std::is_constructible is broken in MSVC until version 2015.
+#if !FMT_MSC_VER || FMT_MSC_VER >= 1900
+struct explicitly_convertible_to_wstring_view {
+  explicit operator fmt::wstring_view() const { return L"foo"; }
+};
+
+TEST(FormatTest, FormatExplicitlyConvertibleToWStringView) {
+  EXPECT_EQ(L"foo",
+            fmt::format(L"{}", explicitly_convertible_to_wstring_view()));
+}
+#endif
+
+namespace fake_qt {
+class QString {
+ public:
+  QString(const wchar_t* s) : s_(std::make_shared<std::wstring>(s)) {}
+  const wchar_t* utf16() const FMT_NOEXCEPT { return s_->data(); }
+  int size() const FMT_NOEXCEPT { return static_cast<int>(s_->size()); }
+
+ private:
+  std::shared_ptr<std::wstring> s_;
+};
+
+fmt::basic_string_view<wchar_t> to_string_view(const QString& s) FMT_NOEXCEPT {
+  return {s.utf16(), static_cast<size_t>(s.size())};
+}
+}  // namespace fake_qt
+
+TEST(FormatTest, FormatForeignStrings) {
+  using fake_qt::QString;
+  EXPECT_EQ(fmt::format(QString(L"{}"), 42), L"42");
+  EXPECT_EQ(fmt::format(QString(L"{}"), QString(L"42")), L"42");
+}
+
 FMT_BEGIN_NAMESPACE
 template <> struct formatter<Date> {
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
     auto it = ctx.begin();
-    if (*it == 'd') ++it;
+    if (it != ctx.end() && *it == 'd') ++it;
     return it;
   }
 
@@ -1649,7 +1511,7 @@ TEST(FormatterTest, CustomFormat) {
 TEST(FormatterTest, CustomFormatTo) {
   char buf[10] = {};
   auto end =
-      &*fmt::format_to(fmt::internal::make_checked(buf, 10), "{}", Answer());
+      &*fmt::format_to(fmt::detail::make_checked(buf, 10), "{}", Answer());
   EXPECT_EQ(end, buf + 2);
   EXPECT_STREQ(buf, "42");
 }
@@ -1759,7 +1621,7 @@ TEST(FormatTest, Print) {
                "Don't panic!");
 #endif
   // Check that the wide print overload compiles.
-  if (fmt::internal::const_check(false)) fmt::print(L"test");
+  if (fmt::detail::const_check(false)) fmt::print(L"test");
 }
 
 TEST(FormatTest, Variadic) {
@@ -1770,9 +1632,9 @@ TEST(FormatTest, Variadic) {
 TEST(FormatTest, Dynamic) {
   typedef fmt::format_context ctx;
   std::vector<fmt::basic_format_arg<ctx>> args;
-  args.emplace_back(fmt::internal::make_arg<ctx>(42));
-  args.emplace_back(fmt::internal::make_arg<ctx>("abc1"));
-  args.emplace_back(fmt::internal::make_arg<ctx>(1.5f));
+  args.emplace_back(fmt::detail::make_arg<ctx>(42));
+  args.emplace_back(fmt::detail::make_arg<ctx>("abc1"));
+  args.emplace_back(fmt::detail::make_arg<ctx>(1.5f));
 
   std::string result = fmt::vformat(
       "{} and {} and {}",
@@ -1944,10 +1806,10 @@ TEST(FormatTest, StrongEnum) {
 }
 #endif
 
-using buffer_range = fmt::buffer_range<char>;
+using buffer_iterator = fmt::format_context::iterator;
 
 class mock_arg_formatter
-    : public fmt::internal::arg_formatter_base<buffer_range> {
+    : public fmt::detail::arg_formatter_base<buffer_iterator, char> {
  private:
 #if FMT_USE_INT128
   MOCK_METHOD1(call, void(__int128_t value));
@@ -1956,24 +1818,23 @@ class mock_arg_formatter
 #endif
 
  public:
-  typedef fmt::internal::arg_formatter_base<buffer_range> base;
-  typedef buffer_range range;
+  using base = fmt::detail::arg_formatter_base<buffer_iterator, char>;
 
   mock_arg_formatter(fmt::format_context& ctx, fmt::format_parse_context*,
-                     fmt::format_specs* s = nullptr)
-      : base(fmt::internal::get_container(ctx.out()), s, ctx.locale()) {
+                     fmt::format_specs* s = nullptr, const char* = nullptr)
+      : base(ctx.out(), s, ctx.locale()) {
     EXPECT_CALL(*this, call(42));
   }
 
   template <typename T>
-  typename std::enable_if<fmt::internal::is_integral<T>::value, iterator>::type
+  typename std::enable_if<fmt::detail::is_integral<T>::value, iterator>::type
   operator()(T value) {
     call(value);
     return base::operator()(value);
   }
 
   template <typename T>
-  typename std::enable_if<!fmt::internal::is_integral<T>::value, iterator>::type
+  typename std::enable_if<!fmt::detail::is_integral<T>::value, iterator>::type
   operator()(T value) {
     return base::operator()(value);
   }
@@ -1985,7 +1846,9 @@ class mock_arg_formatter
 
 static void custom_vformat(fmt::string_view format_str, fmt::format_args args) {
   fmt::memory_buffer buffer;
-  fmt::vformat_to<mock_arg_formatter>(buffer, format_str, args);
+  fmt::detail::buffer<char>& base = buffer;
+  fmt::vformat_to<mock_arg_formatter>(std::back_inserter(base), format_str,
+                                      args);
 }
 
 template <typename... Args>
@@ -2025,7 +1888,7 @@ TEST(FormatTest, DynamicFormatter) {
                    "cannot switch from manual to automatic argument indexing");
   EXPECT_THROW_MSG(format("{:{0}}", num), format_error,
                    "cannot switch from automatic to manual argument indexing");
-#if FMT_NUMERIC_ALIGN
+#if FMT_DEPRECATED_NUMERIC_ALIGN
   EXPECT_THROW_MSG(format("{:=}", str), format_error,
                    "format specifier requires numeric argument");
 #endif
@@ -2043,9 +1906,30 @@ TEST(FormatTest, DynamicFormatter) {
                    "precision not allowed for this argument type");
 }
 
+namespace adl_test {
+namespace fmt {
+namespace detail {
+struct foo {};
+template <typename, typename OutputIt> void write(OutputIt, foo) = delete;
+}  // namespace detail
+}  // namespace fmt
+}  // namespace adl_test
+
+FMT_BEGIN_NAMESPACE
+template <>
+struct formatter<adl_test::fmt::detail::foo> : formatter<std::string> {
+  template <typename FormatContext>
+  auto format(adl_test::fmt::detail::foo, FormatContext& ctx)
+      -> decltype(ctx.out()) {
+    return formatter<std::string>::format("foo", ctx);
+  }
+};
+FMT_END_NAMESPACE
+
 TEST(FormatTest, ToString) {
   EXPECT_EQ("42", fmt::to_string(42));
   EXPECT_EQ("0x1234", fmt::to_string(reinterpret_cast<void*>(0x1234)));
+  EXPECT_EQ("foo", fmt::to_string(adl_test::fmt::detail::foo()));
 }
 
 TEST(FormatTest, ToWString) { EXPECT_EQ(L"42", fmt::to_wstring(42)); }
@@ -2159,7 +2043,7 @@ struct test_arg_id_handler {
 template <size_t N>
 FMT_CONSTEXPR test_arg_id_handler parse_arg_id(const char (&s)[N]) {
   test_arg_id_handler h;
-  fmt::internal::parse_arg_id(s, s + N, h);
+  fmt::detail::parse_arg_id(s, s + N, h);
   return h;
 }
 
@@ -2180,9 +2064,9 @@ struct test_format_specs_handler {
   fmt::align_t align = fmt::align::none;
   char fill = 0;
   int width = 0;
-  fmt::internal::arg_ref<char> width_ref;
+  fmt::detail::arg_ref<char> width_ref;
   int precision = 0;
-  fmt::internal::arg_ref<char> precision_ref;
+  fmt::detail::arg_ref<char> precision_ref;
   char type = 0;
 
   // Workaround for MSVC2017 bug that results in "expression did not evaluate
@@ -2208,12 +2092,12 @@ struct test_format_specs_handler {
   FMT_CONSTEXPR void on_zero() { res = ZERO; }
 
   FMT_CONSTEXPR void on_width(int w) { width = w; }
-  FMT_CONSTEXPR void on_dynamic_width(fmt::internal::auto_id) {}
+  FMT_CONSTEXPR void on_dynamic_width(fmt::detail::auto_id) {}
   FMT_CONSTEXPR void on_dynamic_width(int index) { width_ref = index; }
   FMT_CONSTEXPR void on_dynamic_width(string_view) {}
 
   FMT_CONSTEXPR void on_precision(int p) { precision = p; }
-  FMT_CONSTEXPR void on_dynamic_precision(fmt::internal::auto_id) {}
+  FMT_CONSTEXPR void on_dynamic_precision(fmt::detail::auto_id) {}
   FMT_CONSTEXPR void on_dynamic_precision(int index) { precision_ref = index; }
   FMT_CONSTEXPR void on_dynamic_precision(string_view) {}
 
@@ -2225,7 +2109,7 @@ struct test_format_specs_handler {
 template <size_t N>
 FMT_CONSTEXPR test_format_specs_handler parse_test_specs(const char (&s)[N]) {
   test_format_specs_handler h;
-  fmt::internal::parse_format_specs(s, s + N, h);
+  fmt::detail::parse_format_specs(s, s + N, h);
   return h;
 }
 
@@ -2259,8 +2143,9 @@ struct test_parse_context {
 };
 
 struct test_context {
-  typedef char char_type;
-  typedef fmt::basic_format_arg<test_context> format_arg;
+  using char_type = char;
+  using format_arg = fmt::basic_format_arg<test_context>;
+  using parse_context_type = fmt::format_parse_context;
 
   template <typename T> struct formatter_type {
     typedef fmt::formatter<T, char_type> type;
@@ -2268,7 +2153,7 @@ struct test_context {
 
   template <typename Id>
   FMT_CONSTEXPR fmt::basic_format_arg<test_context> arg(Id id) {
-    return fmt::internal::make_arg<test_context>(id);
+    return fmt::detail::make_arg<test_context>(id);
   }
 
   void on_error(const char*) {}
@@ -2281,7 +2166,7 @@ FMT_CONSTEXPR fmt::format_specs parse_specs(const char (&s)[N]) {
   auto specs = fmt::format_specs();
   auto parse_ctx = test_parse_context();
   auto ctx = test_context();
-  fmt::internal::specs_handler<test_parse_context, test_context> h(
+  fmt::detail::specs_handler<test_parse_context, test_context> h(
       specs, parse_ctx, ctx);
   parse_format_specs(s, s + N, h);
   return specs;
@@ -2305,11 +2190,11 @@ TEST(FormatTest, ConstexprSpecsHandler) {
 }
 
 template <size_t N>
-FMT_CONSTEXPR fmt::internal::dynamic_format_specs<char> parse_dynamic_specs(
+FMT_CONSTEXPR fmt::detail::dynamic_format_specs<char> parse_dynamic_specs(
     const char (&s)[N]) {
-  fmt::internal::dynamic_format_specs<char> specs;
+  fmt::detail::dynamic_format_specs<char> specs;
   test_parse_context ctx{};
-  fmt::internal::dynamic_specs_handler<test_parse_context> h(specs, ctx);
+  fmt::detail::dynamic_specs_handler<test_parse_context> h(specs, ctx);
   parse_format_specs(s, s + N, h);
   return specs;
 }
@@ -2333,8 +2218,8 @@ TEST(FormatTest, ConstexprDynamicSpecsHandler) {
 
 template <size_t N>
 FMT_CONSTEXPR test_format_specs_handler check_specs(const char (&s)[N]) {
-  fmt::internal::specs_checker<test_format_specs_handler> checker(
-      test_format_specs_handler(), fmt::internal::type::double_type);
+  fmt::detail::specs_checker<test_format_specs_handler> checker(
+      test_format_specs_handler(), fmt::detail::type::double_type);
   parse_format_specs(s, s + N, checker);
   return checker;
 }
@@ -2359,13 +2244,14 @@ TEST(FormatTest, ConstexprSpecsChecker) {
 struct test_format_string_handler {
   FMT_CONSTEXPR void on_text(const char*, const char*) {}
 
-  FMT_CONSTEXPR void on_arg_id() {}
+  FMT_CONSTEXPR int on_arg_id() { return 0; }
 
-  template <typename T> FMT_CONSTEXPR void on_arg_id(T) {}
+  template <typename T> FMT_CONSTEXPR int on_arg_id(T) { return 0; }
 
-  FMT_CONSTEXPR void on_replacement_field(const char*) {}
+  FMT_CONSTEXPR void on_replacement_field(int, const char*) {}
 
-  FMT_CONSTEXPR const char* on_format_specs(const char* begin, const char*) {
+  FMT_CONSTEXPR const char* on_format_specs(int, const char* begin,
+                                            const char*) {
     return begin;
   }
 
@@ -2376,7 +2262,7 @@ struct test_format_string_handler {
 
 template <size_t N> FMT_CONSTEXPR bool parse_string(const char (&s)[N]) {
   test_format_string_handler h;
-  fmt::internal::parse_format_string<true>(fmt::string_view(s, N - 1), h);
+  fmt::detail::parse_format_string<true>(fmt::string_view(s, N - 1), h);
   return !h.error;
 }
 
@@ -2420,8 +2306,10 @@ FMT_CONSTEXPR bool equal(const char* s1, const char* s2) {
 template <typename... Args>
 FMT_CONSTEXPR bool test_error(const char* fmt, const char* expected_error) {
   const char* actual_error = nullptr;
-  fmt::internal::do_check_format_string<char, test_error_handler, Args...>(
-      string_view(fmt, len(fmt)), test_error_handler(actual_error));
+  string_view s(fmt, len(fmt));
+  fmt::detail::format_string_checker<char, test_error_handler, Args...> checker(
+      s, test_error_handler(actual_error));
+  fmt::detail::parse_format_string<true>(s, checker);
   return equal(actual_error, expected_error);
 }
 
@@ -2434,13 +2322,13 @@ TEST(FormatTest, FormatStringErrors) {
   EXPECT_ERROR_NOARGS("foo", nullptr);
   EXPECT_ERROR_NOARGS("}", "unmatched '}' in format string");
   EXPECT_ERROR("{0:s", "unknown format specifier", Date);
-#  if FMT_MSC_VER >= 1916
-  // This causes an internal compiler error in MSVC2017.
+#  if !FMT_MSC_VER || FMT_MSC_VER >= 1916
+  // This causes an detail compiler error in MSVC2017.
   EXPECT_ERROR("{:{<}", "invalid fill character '{'", int);
   EXPECT_ERROR("{:10000000000}", "number is too big", int);
   EXPECT_ERROR("{:.10000000000}", "number is too big", int);
-  EXPECT_ERROR_NOARGS("{:x}", "argument index out of range");
-#    if FMT_NUMERIC_ALIGN
+  EXPECT_ERROR_NOARGS("{:x}", "argument not found");
+#    if FMT_DEPRECATED_NUMERIC_ALIGN
   EXPECT_ERROR("{0:=5", "unknown format specifier", int);
   EXPECT_ERROR("{:=}", "format specifier requires numeric argument",
                const char*);
@@ -2458,6 +2346,8 @@ TEST(FormatTest, FormatStringErrors) {
   EXPECT_ERROR("{:+}", "format specifier requires signed argument", unsigned);
   EXPECT_ERROR("{:-}", "format specifier requires signed argument", unsigned);
   EXPECT_ERROR("{: }", "format specifier requires signed argument", unsigned);
+  EXPECT_ERROR("{:{}}", "argument not found", int);
+  EXPECT_ERROR("{:.{}}", "argument not found", double);
   EXPECT_ERROR("{:.2}", "precision not allowed for this argument type", int);
   EXPECT_ERROR("{:s}", "invalid type specifier", int);
   EXPECT_ERROR("{:s}", "invalid type specifier", bool);
@@ -2480,8 +2370,8 @@ TEST(FormatTest, FormatStringErrors) {
   EXPECT_ERROR("{:.{0x}}", "invalid format string", int);
   EXPECT_ERROR("{:.{-}}", "invalid format string", int);
   EXPECT_ERROR("{:.x}", "missing precision specifier", int);
-  EXPECT_ERROR_NOARGS("{}", "argument index out of range");
-  EXPECT_ERROR("{1}", "argument index out of range", int);
+  EXPECT_ERROR_NOARGS("{}", "argument not found");
+  EXPECT_ERROR("{1}", "argument not found", int);
   EXPECT_ERROR("{1}{}",
                "cannot switch from manual to automatic argument indexing", int,
                int);
@@ -2492,7 +2382,7 @@ TEST(FormatTest, FormatStringErrors) {
 
 TEST(FormatTest, VFormatTo) {
   typedef fmt::format_context context;
-  fmt::basic_format_arg<context> arg = fmt::internal::make_arg<context>(42);
+  fmt::basic_format_arg<context> arg = fmt::detail::make_arg<context>(42);
   fmt::basic_format_args<context> args(&arg, 1);
   std::string s;
   fmt::vformat_to(std::back_inserter(s), "{}", args);
@@ -2502,7 +2392,7 @@ TEST(FormatTest, VFormatTo) {
   EXPECT_EQ("42", s);
 
   typedef fmt::wformat_context wcontext;
-  fmt::basic_format_arg<wcontext> warg = fmt::internal::make_arg<wcontext>(42);
+  fmt::basic_format_arg<wcontext> warg = fmt::detail::make_arg<wcontext>(42);
   fmt::basic_format_args<wcontext> wargs(&warg, 1);
   std::wstring w;
   fmt::vformat_to(std::back_inserter(w), L"{}", wargs);
@@ -2530,7 +2420,7 @@ TEST(FormatTest, EmphasisNonHeaderOnly) {
 }
 
 TEST(FormatTest, CharTraitsIsNotAmbiguous) {
-  // Test that we don't inject internal names into the std namespace.
+  // Test that we don't inject detail names into the std namespace.
   using namespace std;
   char_traits<char>::char_type c;
   (void)c;
@@ -2568,13 +2458,12 @@ template <typename S> std::string from_u8str(const S& str) {
 }
 
 TEST(FormatTest, FormatUTF8Precision) {
-  using str_type = std::basic_string<fmt::internal::char8_type>;
-  str_type format(
-      reinterpret_cast<const fmt::internal::char8_type*>(u8"{:.4}"));
-  str_type str(reinterpret_cast<const fmt::internal::char8_type*>(
+  using str_type = std::basic_string<fmt::detail::char8_type>;
+  str_type format(reinterpret_cast<const fmt::detail::char8_type*>(u8"{:.4}"));
+  str_type str(reinterpret_cast<const fmt::detail::char8_type*>(
       u8"caf\u00e9s"));  // cafés
   auto result = fmt::format(format, str);
-  EXPECT_EQ(fmt::internal::count_code_points(result), 4);
+  EXPECT_EQ(fmt::detail::count_code_points(result), 4);
   EXPECT_EQ(result.size(), 5);
   EXPECT_EQ(from_u8str(result), from_u8str(str.substr(0, 5)));
 }
diff --git a/test/fuzzing/README.md b/test/fuzzing/README.md
index 0499d00c..8f7a4536 100644
--- a/test/fuzzing/README.md
+++ b/test/fuzzing/README.md
@@ -7,14 +7,19 @@ in fmt. It is a part of the continous fuzzing at
 The source code is modified to make the fuzzing possible without locking up on
 resource exhaustion:
 ```cpp
-#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+#ifdef FMT_FUZZ
 if(spec.precision>100000) {
   throw std::runtime_error("fuzz mode - avoiding large precision");
 }
 #endif
-```
-This macro is the defacto standard for making fuzzing practically possible, see
-[the libFuzzer documentation](https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode).
+``` 
+This macro `FMT_FUZZ` is enabled on OSS-Fuzz builds and makes fuzzing
+practically possible. It is used in fmt code to prevent resource exhaustion in
+fuzzing mode.  
+The macro `FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION` is the
+defacto standard for making fuzzing practically possible to disable certain
+fuzzing-unfriendly features (for example, randomness), see [the libFuzzer
+documentation](https://llvm.org/docs/LibFuzzer.html#fuzzer-friendly-build-mode).
 
 ## Running the fuzzers locally
 
diff --git a/test/fuzzing/chrono_duration.cpp b/test/fuzzing/chrono_duration.cpp
index d1de9ae6..3f25f6be 100644
--- a/test/fuzzing/chrono_duration.cpp
+++ b/test/fuzzing/chrono_duration.cpp
@@ -25,7 +25,7 @@ void invoke_inner(fmt::string_view formatstring, const Item item) {
 
 // Item is the underlying type for duration (int, long etc)
 template <typename Item>
-void invoke_outer(const uint8_t* Data, std::size_t Size, const int scaling) {
+void invoke_outer(const uint8_t* Data, size_t Size, const int scaling) {
   // always use a fixed location of the data
   using fmt_fuzzer::Nfixed;
 
@@ -97,7 +97,7 @@ void invoke_outer(const uint8_t* Data, std::size_t Size, const int scaling) {
   // doit_impl<Item,std::yotta>(buf.data(),item);
 }
 
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, size_t Size) {
   if (Size <= 4) {
     return 0;
   }
diff --git a/test/fuzzing/main.cpp b/test/fuzzing/main.cpp
index 6ac81302..1053eeeb 100644
--- a/test/fuzzing/main.cpp
+++ b/test/fuzzing/main.cpp
@@ -4,7 +4,7 @@
 #include <vector>
 #include "fuzzer_common.h"
 
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size);
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, size_t Size);
 int main(int argc, char* argv[]) {
   for (int i = 1; i < argc; ++i) {
     std::ifstream in(argv[i]);
@@ -13,7 +13,7 @@ int main(int argc, char* argv[]) {
     const auto pos = in.tellg();
     assert(pos >= 0);
     in.seekg(0, std::ios_base::beg);
-    std::vector<char> buf(static_cast<std::size_t>(pos));
+    std::vector<char> buf(static_cast<size_t>(pos));
     in.read(buf.data(), static_cast<long>(buf.size()));
     assert(in.gcount() == pos);
     LLVMFuzzerTestOneInput(fmt_fuzzer::as_bytes(buf.data()), buf.size());
diff --git a/test/fuzzing/named_arg.cpp b/test/fuzzing/named_arg.cpp
index 0f9a451b..bd0cb686 100644
--- a/test/fuzzing/named_arg.cpp
+++ b/test/fuzzing/named_arg.cpp
@@ -10,7 +10,7 @@
 #include "fuzzer_common.h"
 
 template <typename Item1>
-void invoke_fmt(const uint8_t* Data, std::size_t Size, unsigned int argsize) {
+void invoke_fmt(const uint8_t* Data, size_t Size, unsigned int argsize) {
   constexpr auto N1 = sizeof(Item1);
   static_assert(N1 <= fmt_fuzzer::Nfixed, "Nfixed too small");
   if (Size <= fmt_fuzzer::Nfixed) {
@@ -29,11 +29,11 @@ void invoke_fmt(const uint8_t* Data, std::size_t Size, unsigned int argsize) {
   // allocating buffers separately is slower, but increases chances
   // of detecting memory errors
 #if FMT_FUZZ_SEPARATE_ALLOCATION
-  std::vector<char> argnamebuffer(argsize);
+  std::vector<char> argnamebuffer(argsize + 1);
   std::memcpy(argnamebuffer.data(), Data, argsize);
-  auto argname = fmt::string_view(argnamebuffer.data(), argsize);
+  auto argname = argnamebuffer.data();
 #else
-  auto argname = fmt::string_view(fmt_fuzzer::as_chars(Data), argsize);
+  auto argname = fmt_fuzzer::as_chars(Data);
 #endif
   Data += argsize;
   Size -= argsize;
@@ -105,7 +105,7 @@ template <typename Callback> void invoke(int index, Callback callback) {
   }
 }
 
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, size_t Size) {
   if (Size <= 3) {
     return 0;
   }
diff --git a/test/fuzzing/one_arg.cpp b/test/fuzzing/one_arg.cpp
index 86a159be..3a1bf5cc 100644
--- a/test/fuzzing/one_arg.cpp
+++ b/test/fuzzing/one_arg.cpp
@@ -13,7 +13,7 @@
 using fmt_fuzzer::Nfixed;
 
 template <typename Item>
-void invoke_fmt(const uint8_t* Data, std::size_t Size) {
+void invoke_fmt(const uint8_t* Data, size_t Size) {
   constexpr auto N = sizeof(Item);
   static_assert(N <= Nfixed, "Nfixed is too small");
   if (Size <= Nfixed) {
@@ -40,7 +40,7 @@ void invoke_fmt(const uint8_t* Data, std::size_t Size) {
 #endif
 }
 
-void invoke_fmt_time(const uint8_t* Data, std::size_t Size) {
+void invoke_fmt_time(const uint8_t* Data, size_t Size) {
   using Item = std::time_t;
   constexpr auto N = sizeof(Item);
   static_assert(N <= Nfixed, "Nfixed too small");
@@ -69,7 +69,7 @@ void invoke_fmt_time(const uint8_t* Data, std::size_t Size) {
   }
 }
 
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, size_t Size) {
   if (Size <= 3) {
     return 0;
   }
diff --git a/test/fuzzing/sprintf.cpp b/test/fuzzing/sprintf.cpp
index 7dd02221..aa028756 100644
--- a/test/fuzzing/sprintf.cpp
+++ b/test/fuzzing/sprintf.cpp
@@ -10,7 +10,7 @@
 using fmt_fuzzer::Nfixed;
 
 template <typename Item1, typename Item2>
-void invoke_fmt(const uint8_t* Data, std::size_t Size) {
+void invoke_fmt(const uint8_t* Data, size_t Size) {
   constexpr auto N1 = sizeof(Item1);
   constexpr auto N2 = sizeof(Item2);
   static_assert(N1 <= Nfixed, "size1 exceeded");
@@ -90,7 +90,7 @@ template <typename Callback> void invoke(int index, Callback callback) {
   }
 }
 
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, size_t Size) {
   if (Size <= 3) {
     return 0;
   }
diff --git a/test/fuzzing/two_args.cpp b/test/fuzzing/two_args.cpp
index 72b035cc..af3495ce 100644
--- a/test/fuzzing/two_args.cpp
+++ b/test/fuzzing/two_args.cpp
@@ -10,7 +10,7 @@
 constexpr auto Nfixed = fmt_fuzzer::Nfixed;
 
 template <typename Item1, typename Item2>
-void invoke_fmt(const uint8_t* Data, std::size_t Size) {
+void invoke_fmt(const uint8_t* Data, size_t Size) {
   constexpr auto N1 = sizeof(Item1);
   constexpr auto N2 = sizeof(Item2);
   static_assert(N1 <= Nfixed, "size1 exceeded");
@@ -86,7 +86,7 @@ template <typename Callback> void invoke(int index, Callback callback) {
   }
 }
 
-extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, std::size_t Size) {
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* Data, size_t Size) {
   if (Size <= 3) {
     return 0;
   }
diff --git a/test/gmock-gtest-all.cc b/test/gmock-gtest-all.cc
index 980cc60e..bc43f930 100644
--- a/test/gmock-gtest-all.cc
+++ b/test/gmock-gtest-all.cc
@@ -344,6 +344,7 @@ class GTEST_API_ SingleFailureChecker {
 #  include <sys/mman.h>  // NOLINT
 #  include <sys/time.h>  // NOLINT
 #  include <unistd.h>    // NOLINT
+
 #  include <string>
 
 #elif GTEST_OS_SYMBIAN
@@ -7728,6 +7729,7 @@ InternalRunDeathTestFlag* ParseInternalRunDeathTestFlag() {
 #  include <sys/syslimits.h>
 #else
 #  include <limits.h>
+
 #  include <climits>  // Some Linux distributions define PATH_MAX here.
 #endif                // GTEST_OS_WINDOWS_MOBILE
 
@@ -8899,6 +8901,7 @@ const char* StringFromGTestEnv(const char* flag, const char* default_value) {
 
 #include <ctype.h>
 #include <stdio.h>
+
 #include <ostream>  // NOLINT
 #include <string>
 
@@ -9494,6 +9497,7 @@ const char* TypedTestCasePState::VerifyRegisteredTestNames(
 // This file implements cardinalities.
 
 #include <limits.h>
+
 #include <ostream>  // NOLINT
 #include <sstream>
 #include <string>
@@ -9646,6 +9650,7 @@ GTEST_API_ Cardinality Exactly(int n) { return Between(n, n); }
 // USE THEM IN USER CODE.
 
 #include <ctype.h>
+
 #include <ostream>  // NOLINT
 #include <string>
 
@@ -9808,6 +9813,7 @@ GTEST_API_ void Log(LogSeverity severity, const string& message,
 // utilities for defining matchers.
 
 #include <string.h>
+
 #include <sstream>
 #include <string>
 
@@ -10291,6 +10297,7 @@ bool UnorderedElementsAreMatcherImplBase::
 // EXPECT_CALL).
 
 #include <stdlib.h>
+
 #include <iostream>  // NOLINT
 #include <map>
 #include <set>
diff --git a/test/gtest-extra-test.cc b/test/gtest-extra-test.cc
index 99d1d03a..ea728607 100644
--- a/test/gtest-extra-test.cc
+++ b/test/gtest-extra-test.cc
@@ -8,6 +8,7 @@
 #include "gtest-extra.h"
 
 #include <gtest/gtest-spi.h>
+
 #include <algorithm>
 #include <cstring>
 #include <memory>
@@ -167,22 +168,24 @@ TEST_F(SingleEvaluationTest, FailedEXPECT_WRITE) {
 // Tests that assertion arguments are evaluated exactly once.
 TEST_F(SingleEvaluationTest, WriteTests) {
   // successful EXPECT_WRITE
-  EXPECT_WRITE(stdout,
-               {  // NOLINT
-                 a_++;
-                 std::printf("test");
-               },
-               (b_++, "test"));
+  EXPECT_WRITE(
+      stdout,
+      {  // NOLINT
+        a_++;
+        std::printf("test");
+      },
+      (b_++, "test"));
   EXPECT_EQ(1, a_);
   EXPECT_EQ(1, b_);
 
   // failed EXPECT_WRITE
-  EXPECT_NONFATAL_FAILURE(EXPECT_WRITE(stdout,
-                                       {  // NOLINT
-                                         a_++;
-                                         std::printf("test");
-                                       },
-                                       (b_++, "other")),
+  EXPECT_NONFATAL_FAILURE(EXPECT_WRITE(
+                              stdout,
+                              {  // NOLINT
+                                a_++;
+                                std::printf("test");
+                              },
+                              (b_++, "other")),
                           "Actual: test");
   EXPECT_EQ(2, a_);
   EXPECT_EQ(2, b_);
@@ -417,16 +420,17 @@ TEST(OutputRedirectTest, ErrorInDtor) {
   std::unique_ptr<OutputRedirect> redir(new OutputRedirect(f.get()));
   // Put a character in a file buffer.
   EXPECT_EQ('x', fputc('x', f.get()));
-  EXPECT_WRITE(stderr,
-               {
-                 // The close function must be called inside EXPECT_WRITE,
-                 // otherwise the system may recycle closed file descriptor when
-                 // redirecting the output in EXPECT_STDERR and the second close
-                 // will break output redirection.
-                 FMT_POSIX(close(write_fd));
-                 SUPPRESS_ASSERT(redir.reset(nullptr));
-               },
-               format_system_error(EBADF, "cannot flush stream"));
+  EXPECT_WRITE(
+      stderr,
+      {
+        // The close function must be called inside EXPECT_WRITE,
+        // otherwise the system may recycle closed file descriptor when
+        // redirecting the output in EXPECT_STDERR and the second close
+        // will break output redirection.
+        FMT_POSIX(close(write_fd));
+        SUPPRESS_ASSERT(redir.reset(nullptr));
+      },
+      format_system_error(EBADF, "cannot flush stream"));
   write_copy.dup2(write_fd);  // "undo" close or dtor of buffered_file will fail
 }
 
diff --git a/test/gtest-extra.cc b/test/gtest-extra.cc
index cf92852b..58628a8a 100644
--- a/test/gtest-extra.cc
+++ b/test/gtest-extra.cc
@@ -57,7 +57,7 @@ std::string OutputRedirect::restore_and_read() {
   if (read_end_.descriptor() == -1) return content;  // Already read.
   enum { BUFFER_SIZE = 4096 };
   char buffer[BUFFER_SIZE];
-  std::size_t count = 0;
+  size_t count = 0;
   do {
     count = read_end_.read(buffer, BUFFER_SIZE);
     content.append(buffer, count);
@@ -66,9 +66,9 @@ std::string OutputRedirect::restore_and_read() {
   return content;
 }
 
-std::string read(file& f, std::size_t count) {
+std::string read(file& f, size_t count) {
   std::string buffer(count, '\0');
-  std::size_t n = 0, offset = 0;
+  size_t n = 0, offset = 0;
   do {
     n = f.read(&buffer[offset], count - offset);
     // We can't read more than size_t bytes since count has type size_t.
diff --git a/test/gtest-extra.h b/test/gtest-extra.h
index 3b84d448..3ed8052b 100644
--- a/test/gtest-extra.h
+++ b/test/gtest-extra.h
@@ -9,8 +9,9 @@
 #define FMT_GTEST_EXTRA_H_
 
 #include <string>
-#include "gmock.h"
+
 #include "fmt/os.h"
+#include "gmock.h"
 
 #define FMT_TEST_THROW_(statement, expected_exception, expected_message, fail) \
   GTEST_AMBIGUOUS_ELSE_BLOCKER_                                                \
@@ -137,10 +138,11 @@ class SuppressAssert {
     EXPECT_SYSTEM_ERROR(SUPPRESS_ASSERT(statement), error_code, message)
 
 // Attempts to read count characters from a file.
-std::string read(fmt::file& f, std::size_t count);
+std::string read(fmt::file& f, size_t count);
 
 #  define EXPECT_READ(file, expected_content) \
-    EXPECT_EQ(expected_content, read(file, std::strlen(expected_content)))
+    EXPECT_EQ(expected_content, \
+              read(file, fmt::string_view(expected_content).size()))
 
 #else
 #  define EXPECT_WRITE(file, statement, expected_output) SUCCEED()
diff --git a/test/locale-test.cc b/test/locale-test.cc
index a064ecda..af3078af 100644
--- a/test/locale-test.cc
+++ b/test/locale-test.cc
@@ -6,9 +6,10 @@
 // For the license information refer to format.h.
 
 #include "fmt/locale.h"
+
 #include "gmock.h"
 
-using fmt::internal::max_value;
+using fmt::detail::max_value;
 
 #ifndef FMT_STATIC_THOUSANDS_SEPARATOR
 template <typename Char> struct numpunct : std::numpunct<Char> {
@@ -41,49 +42,68 @@ template <typename Char> struct small_grouping : std::numpunct<Char> {
 
 TEST(LocaleTest, DoubleDecimalPoint) {
   std::locale loc(std::locale(), new numpunct<char>());
-  EXPECT_EQ("1?23", fmt::format(loc, "{:n}", 1.23));
+  EXPECT_EQ("1?23", fmt::format(loc, "{:L}", 1.23));
 }
 
 TEST(LocaleTest, Format) {
   std::locale loc(std::locale(), new numpunct<char>());
-  EXPECT_EQ("1234567", fmt::format(std::locale(), "{:n}", 1234567));
-  EXPECT_EQ("1~234~567", fmt::format(loc, "{:n}", 1234567));
+  EXPECT_EQ("1234567", fmt::format(std::locale(), "{:L}", 1234567));
+  EXPECT_EQ("1~234~567", fmt::format(loc, "{:L}", 1234567));
+  EXPECT_EQ("-1~234~567", fmt::format(loc, "{:L}", -1234567));
   fmt::format_arg_store<fmt::format_context, int> as{1234567};
-  EXPECT_EQ("1~234~567", fmt::vformat(loc, "{:n}", fmt::format_args(as)));
+  EXPECT_EQ("1~234~567", fmt::vformat(loc, "{:L}", fmt::format_args(as)));
   std::string s;
-  fmt::format_to(std::back_inserter(s), loc, "{:n}", 1234567);
+  fmt::format_to(std::back_inserter(s), loc, "{:L}", 1234567);
   EXPECT_EQ("1~234~567", s);
 
   std::locale no_grouping_loc(std::locale(), new no_grouping<char>());
-  EXPECT_EQ("1234567", fmt::format(no_grouping_loc, "{:n}", 1234567));
+  EXPECT_EQ("1234567", fmt::format(no_grouping_loc, "{:L}", 1234567));
 
   std::locale special_grouping_loc(std::locale(), new special_grouping<char>());
-  EXPECT_EQ("1,23,45,678", fmt::format(special_grouping_loc, "{:n}", 12345678));
+  EXPECT_EQ("1,23,45,678", fmt::format(special_grouping_loc, "{:L}", 12345678));
+  EXPECT_EQ("12,345", fmt::format(special_grouping_loc, "{:L}", 12345));
 
   std::locale small_grouping_loc(std::locale(), new small_grouping<char>());
   EXPECT_EQ("4,2,9,4,9,6,7,2,9,5",
-            fmt::format(small_grouping_loc, "{:n}", max_value<uint32_t>()));
+            fmt::format(small_grouping_loc, "{:L}", max_value<uint32_t>()));
+}
+
+TEST(LocaleTest, FormatDetaultAlign) {
+  std::locale special_grouping_loc(std::locale(), new special_grouping<char>());
+  EXPECT_EQ("  12,345", fmt::format(special_grouping_loc, "{:8L}", 12345));
 }
 
 TEST(LocaleTest, WFormat) {
   std::locale loc(std::locale(), new numpunct<wchar_t>());
-  EXPECT_EQ(L"1234567", fmt::format(std::locale(), L"{:n}", 1234567));
-  EXPECT_EQ(L"1~234~567", fmt::format(loc, L"{:n}", 1234567));
+  EXPECT_EQ(L"1234567", fmt::format(std::locale(), L"{:L}", 1234567));
+  EXPECT_EQ(L"1~234~567", fmt::format(loc, L"{:L}", 1234567));
   fmt::format_arg_store<fmt::wformat_context, int> as{1234567};
-  EXPECT_EQ(L"1~234~567", fmt::vformat(loc, L"{:n}", fmt::wformat_args(as)));
-  EXPECT_EQ(L"1234567", fmt::format(std::locale("C"), L"{:n}", 1234567));
+  EXPECT_EQ(L"1~234~567", fmt::vformat(loc, L"{:L}", fmt::wformat_args(as)));
+  EXPECT_EQ(L"1234567", fmt::format(std::locale("C"), L"{:L}", 1234567));
 
   std::locale no_grouping_loc(std::locale(), new no_grouping<wchar_t>());
-  EXPECT_EQ(L"1234567", fmt::format(no_grouping_loc, L"{:n}", 1234567));
+  EXPECT_EQ(L"1234567", fmt::format(no_grouping_loc, L"{:L}", 1234567));
 
   std::locale special_grouping_loc(std::locale(),
                                    new special_grouping<wchar_t>());
   EXPECT_EQ(L"1,23,45,678",
-            fmt::format(special_grouping_loc, L"{:n}", 12345678));
+            fmt::format(special_grouping_loc, L"{:L}", 12345678));
 
   std::locale small_grouping_loc(std::locale(), new small_grouping<wchar_t>());
   EXPECT_EQ(L"4,2,9,4,9,6,7,2,9,5",
-            fmt::format(small_grouping_loc, L"{:n}", max_value<uint32_t>()));
+            fmt::format(small_grouping_loc, L"{:L}", max_value<uint32_t>()));
+}
+
+TEST(LocaleTest, DoubleFormatter) {
+  auto loc = std::locale(std::locale(), new special_grouping<char>());
+  auto f = fmt::formatter<int>();
+  auto parse_ctx = fmt::format_parse_context("L");
+  f.parse(parse_ctx);
+  char buf[10] = {};
+  fmt::basic_format_context<char*, char> format_ctx(
+      buf, {}, fmt::detail::locale_ref(loc));
+  *f.format(12345, format_ctx) = 0;
+  EXPECT_STREQ("12,345", buf);
 }
 
 #endif  // FMT_STATIC_THOUSANDS_SEPARATOR
diff --git a/test/mock-allocator.h b/test/mock-allocator.h
index 1dd2dadb..513a62e8 100644
--- a/test/mock-allocator.h
+++ b/test/mock-allocator.h
@@ -16,8 +16,8 @@ template <typename T> class mock_allocator {
   mock_allocator() {}
   mock_allocator(const mock_allocator&) {}
   typedef T value_type;
-  MOCK_METHOD1_T(allocate, T*(std::size_t n));
-  MOCK_METHOD2_T(deallocate, void(T* p, std::size_t n));
+  MOCK_METHOD1_T(allocate, T*(size_t n));
+  MOCK_METHOD2_T(deallocate, void(T* p, size_t n));
 };
 
 template <typename Allocator> class allocator_ref {
@@ -51,10 +51,10 @@ template <typename Allocator> class allocator_ref {
  public:
   Allocator* get() const { return alloc_; }
 
-  value_type* allocate(std::size_t n) {
+  value_type* allocate(size_t n) {
     return std::allocator_traits<Allocator>::allocate(*alloc_, n);
   }
-  void deallocate(value_type* p, std::size_t n) { alloc_->deallocate(p, n); }
+  void deallocate(value_type* p, size_t n) { alloc_->deallocate(p, n); }
 };
 
 #endif  // FMT_MOCK_ALLOCATOR_H_
diff --git a/test/os-test.cc b/test/os-test.cc
index ee963087..186198ef 100644
--- a/test/os-test.cc
+++ b/test/os-test.cc
@@ -5,11 +5,12 @@
 //
 // For the license information refer to format.h.
 
+#include "fmt/os.h"
+
 #include <cstdlib>  // std::exit
 #include <cstring>
 #include <memory>
 
-#include "fmt/os.h"
 #include "gtest-extra.h"
 #include "util.h"
 
@@ -26,14 +27,14 @@ using fmt::error_code;
 
 TEST(UtilTest, UTF16ToUTF8) {
   std::string s = "ёжик";
-  fmt::internal::utf16_to_utf8 u(L"\x0451\x0436\x0438\x043A");
+  fmt::detail::utf16_to_utf8 u(L"\x0451\x0436\x0438\x043A");
   EXPECT_EQ(s, u.str());
   EXPECT_EQ(s.size(), u.size());
 }
 
 TEST(UtilTest, UTF16ToUTF8EmptyString) {
   std::string s = "";
-  fmt::internal::utf16_to_utf8 u(L"");
+  fmt::detail::utf16_to_utf8 u(L"");
   EXPECT_EQ(s, u.str());
   EXPECT_EQ(s.size(), u.size());
 }
@@ -43,7 +44,7 @@ void check_utf_conversion_error(
     const char* message,
     fmt::basic_string_view<Char> str = fmt::basic_string_view<Char>(0, 1)) {
   fmt::memory_buffer out;
-  fmt::internal::format_windows_error(out, ERROR_INVALID_PARAMETER, message);
+  fmt::detail::format_windows_error(out, ERROR_INVALID_PARAMETER, message);
   fmt::system_error error(0, "");
   try {
     (Converter)(str);
@@ -55,12 +56,12 @@ void check_utf_conversion_error(
 }
 
 TEST(UtilTest, UTF16ToUTF8Error) {
-  check_utf_conversion_error<fmt::internal::utf16_to_utf8, wchar_t>(
+  check_utf_conversion_error<fmt::detail::utf16_to_utf8, wchar_t>(
       "cannot convert string from UTF-16 to UTF-8");
 }
 
 TEST(UtilTest, UTF16ToUTF8Convert) {
-  fmt::internal::utf16_to_utf8 u;
+  fmt::detail::utf16_to_utf8 u;
   EXPECT_EQ(ERROR_INVALID_PARAMETER, u.convert(fmt::wstring_view(0, 1)));
   EXPECT_EQ(ERROR_INVALID_PARAMETER,
             u.convert(fmt::wstring_view(L"foo", INT_MAX + 1u)));
@@ -73,17 +74,16 @@ TEST(UtilTest, FormatWindowsError) {
                  0, ERROR_FILE_EXISTS,
                  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                  reinterpret_cast<LPWSTR>(&message), 0, 0);
-  fmt::internal::utf16_to_utf8 utf8_message(message);
+  fmt::detail::utf16_to_utf8 utf8_message(message);
   LocalFree(message);
   fmt::memory_buffer actual_message;
-  fmt::internal::format_windows_error(actual_message, ERROR_FILE_EXISTS,
-                                      "test");
+  fmt::detail::format_windows_error(actual_message, ERROR_FILE_EXISTS, "test");
   EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
             fmt::to_string(actual_message));
   actual_message.resize(0);
-  auto max_size = fmt::internal::max_value<size_t>();
-  fmt::internal::format_windows_error(actual_message, ERROR_FILE_EXISTS,
-                                      fmt::string_view(0, max_size));
+  auto max_size = fmt::detail::max_value<size_t>();
+  fmt::detail::format_windows_error(actual_message, ERROR_FILE_EXISTS,
+                                    fmt::string_view(0, max_size));
   EXPECT_EQ(fmt::format("error {}", ERROR_FILE_EXISTS),
             fmt::to_string(actual_message));
 }
@@ -103,11 +103,11 @@ TEST(UtilTest, FormatLongWindowsError) {
                      reinterpret_cast<LPWSTR>(&message), 0, 0) == 0) {
     return;
   }
-  fmt::internal::utf16_to_utf8 utf8_message(message);
+  fmt::detail::utf16_to_utf8 utf8_message(message);
   LocalFree(message);
   fmt::memory_buffer actual_message;
-  fmt::internal::format_windows_error(actual_message, provisioning_not_allowed,
-                                      "test");
+  fmt::detail::format_windows_error(actual_message, provisioning_not_allowed,
+                                    "test");
   EXPECT_EQ(fmt::format("test: {}", utf8_message.str()),
             fmt::to_string(actual_message));
 }
@@ -120,14 +120,14 @@ TEST(UtilTest, WindowsError) {
     error = e;
   }
   fmt::memory_buffer message;
-  fmt::internal::format_windows_error(message, ERROR_FILE_EXISTS, "test error");
+  fmt::detail::format_windows_error(message, ERROR_FILE_EXISTS, "test error");
   EXPECT_EQ(to_string(message), error.what());
   EXPECT_EQ(ERROR_FILE_EXISTS, error.error_code());
 }
 
 TEST(UtilTest, ReportWindowsError) {
   fmt::memory_buffer out;
-  fmt::internal::format_windows_error(out, ERROR_FILE_EXISTS, "test error");
+  fmt::detail::format_windows_error(out, ERROR_FILE_EXISTS, "test error");
   out.push_back('\n');
   EXPECT_WRITE(stderr,
                fmt::report_windows_error(ERROR_FILE_EXISTS, "test error"),
@@ -164,10 +164,10 @@ static file open_file() {
 
 // Attempts to write a string to a file.
 static void write(file& f, fmt::string_view s) {
-  std::size_t num_chars_left = s.size();
+  size_t num_chars_left = s.size();
   const char* ptr = s.data();
   do {
-    std::size_t count = f.write(ptr, num_chars_left);
+    size_t count = f.write(ptr, num_chars_left);
     ptr += count;
     // We can't write more than size_t bytes since num_chars_left
     // has type size_t.
@@ -238,16 +238,17 @@ TEST(BufferedFileTest, CloseFileInDtor) {
 
 TEST(BufferedFileTest, CloseErrorInDtor) {
   std::unique_ptr<buffered_file> f(new buffered_file(open_buffered_file()));
-  EXPECT_WRITE(stderr,
-               {
-                 // The close function must be called inside EXPECT_WRITE,
-                 // otherwise the system may recycle closed file descriptor when
-                 // redirecting the output in EXPECT_STDERR and the second close
-                 // will break output redirection.
-                 FMT_POSIX(close(f->fileno()));
-                 SUPPRESS_ASSERT(f.reset(nullptr));
-               },
-               format_system_error(EBADF, "cannot close file") + "\n");
+  EXPECT_WRITE(
+      stderr,
+      {
+        // The close function must be called inside EXPECT_WRITE,
+        // otherwise the system may recycle closed file descriptor when
+        // redirecting the output in EXPECT_STDERR and the second close
+        // will break output redirection.
+        FMT_POSIX(close(f->fileno()));
+        SUPPRESS_ASSERT(f.reset(nullptr));
+      },
+      format_system_error(EBADF, "cannot close file") + "\n");
 }
 
 TEST(BufferedFileTest, Close) {
@@ -286,6 +287,26 @@ TEST(BufferedFileTest, Fileno) {
   EXPECT_READ(copy, FILE_CONTENT);
 }
 
+TEST(DirectBufferedFileTest, Print) {
+  fmt::direct_buffered_file out(
+    "test-file", fmt::file::WRONLY | fmt::file::CREATE);
+  fmt::print(out, "The answer is {}.\n", 42);
+  out.close();
+  file in("test-file", file::RDONLY);
+  EXPECT_READ(in, "The answer is 42.\n");
+}
+
+TEST(DirectBufferedFileTest, BufferBoundary) {
+  auto str = std::string(4096, 'x');
+  fmt::direct_buffered_file out(
+    "test-file", fmt::file::WRONLY | fmt::file::CREATE);
+  fmt::print(out, "{}", str);
+  fmt::print(out, "{}", str);
+  out.close();
+  file in("test-file", file::RDONLY);
+  EXPECT_READ(in, str + str);
+}
+
 TEST(FileTest, DefaultCtor) {
   file f;
   EXPECT_EQ(-1, f.descriptor());
@@ -369,16 +390,17 @@ TEST(FileTest, CloseFileInDtor) {
 
 TEST(FileTest, CloseErrorInDtor) {
   std::unique_ptr<file> f(new file(open_file()));
-  EXPECT_WRITE(stderr,
-               {
-                 // The close function must be called inside EXPECT_WRITE,
-                 // otherwise the system may recycle closed file descriptor when
-                 // redirecting the output in EXPECT_STDERR and the second close
-                 // will break output redirection.
-                 FMT_POSIX(close(f->descriptor()));
-                 SUPPRESS_ASSERT(f.reset(nullptr));
-               },
-               format_system_error(EBADF, "cannot close file") + "\n");
+  EXPECT_WRITE(
+      stderr,
+      {
+        // The close function must be called inside EXPECT_WRITE,
+        // otherwise the system may recycle closed file descriptor when
+        // redirecting the output in EXPECT_STDERR and the second close
+        // will break output redirection.
+        FMT_POSIX(close(f->descriptor()));
+        SUPPRESS_ASSERT(f.reset(nullptr));
+      },
+      format_system_error(EBADF, "cannot close file") + "\n");
 }
 
 TEST(FileTest, Close) {
@@ -495,4 +517,4 @@ TEST(LocaleTest, Strtod) {
   EXPECT_EQ(start + 3, ptr);
 }
 #  endif
-#endif  // FMT_USE_FCNTL
\ No newline at end of file
+#endif  // FMT_USE_FCNTL
diff --git a/test/ostream-test.cc b/test/ostream-test.cc
index d9329345..1c87d46d 100644
--- a/test/ostream-test.cc
+++ b/test/ostream-test.cc
@@ -21,9 +21,9 @@ template <> struct formatter<test> : formatter<int> {
 };
 }  // namespace fmt
 
-#include "fmt/ostream.h"
-
 #include <sstream>
+
+#include "fmt/ostream.h"
 #include "gmock.h"
 #include "gtest-extra.h"
 #include "util.h"
@@ -64,22 +64,23 @@ TEST(OStreamTest, Enum) {
   EXPECT_EQ(L"0", fmt::format(L"{}", unstreamable_enum()));
 }
 
-using range = fmt::buffer_range<char>;
-
-struct test_arg_formatter : fmt::arg_formatter<range> {
+struct test_arg_formatter
+    : fmt::detail::arg_formatter<fmt::format_context::iterator, char> {
   fmt::format_parse_context parse_ctx;
   test_arg_formatter(fmt::format_context& ctx, fmt::format_specs& s)
-      : fmt::arg_formatter<range>(ctx, &parse_ctx, &s), parse_ctx("") {}
+      : fmt::detail::arg_formatter<fmt::format_context::iterator, char>(
+            ctx, &parse_ctx, &s),
+        parse_ctx("") {}
 };
 
 TEST(OStreamTest, CustomArg) {
   fmt::memory_buffer buffer;
-  fmt::internal::buffer<char>& base = buffer;
+  fmt::detail::buffer<char>& base = buffer;
   fmt::format_context ctx(std::back_inserter(base), fmt::format_args());
   fmt::format_specs spec;
   test_arg_formatter af(ctx, spec);
   fmt::visit_format_arg(
-      af, fmt::internal::make_arg<fmt::format_context>(streamable_enum()));
+      af, fmt::detail::make_arg<fmt::format_context>(streamable_enum()));
   EXPECT_EQ("streamable_enum", std::string(buffer.data(), buffer.size()));
 }
 
@@ -95,7 +96,7 @@ TEST(OStreamTest, Format) {
 TEST(OStreamTest, FormatSpecs) {
   EXPECT_EQ("def  ", format("{0:<5}", TestString("def")));
   EXPECT_EQ("  def", format("{0:>5}", TestString("def")));
-#if FMT_NUMERIC_ALIGN
+#if FMT_DEPRECATED_NUMERIC_ALIGN
   EXPECT_THROW_MSG(format("{0:=5}", TestString("def")), format_error,
                    "format specifier requires numeric argument");
 #endif
@@ -140,18 +141,18 @@ TEST(OStreamTest, WriteToOStream) {
   fmt::memory_buffer buffer;
   const char* foo = "foo";
   buffer.append(foo, foo + std::strlen(foo));
-  fmt::internal::write(os, buffer);
+  fmt::detail::write_buffer(os, buffer);
   EXPECT_EQ("foo", os.str());
 }
 
 TEST(OStreamTest, WriteToOStreamMaxSize) {
-  std::size_t max_size = fmt::internal::max_value<std::size_t>();
-  std::streamsize max_streamsize = fmt::internal::max_value<std::streamsize>();
-  if (max_size <= fmt::internal::to_unsigned(max_streamsize)) return;
+  size_t max_size = fmt::detail::max_value<size_t>();
+  std::streamsize max_streamsize = fmt::detail::max_value<std::streamsize>();
+  if (max_size <= fmt::detail::to_unsigned(max_streamsize)) return;
 
-  struct test_buffer : fmt::internal::buffer<char> {
-    explicit test_buffer(std::size_t size) { resize(size); }
-    void grow(std::size_t) {}
+  struct test_buffer : fmt::detail::buffer<char> {
+    explicit test_buffer(size_t size) { resize(size); }
+    void grow(size_t) {}
   } buffer(max_size);
 
   struct mock_streambuf : std::streambuf {
@@ -171,13 +172,13 @@ TEST(OStreamTest, WriteToOStreamMaxSize) {
   typedef std::make_unsigned<std::streamsize>::type ustreamsize;
   ustreamsize size = max_size;
   do {
-    auto n = std::min(size, fmt::internal::to_unsigned(max_streamsize));
+    auto n = std::min(size, fmt::detail::to_unsigned(max_streamsize));
     EXPECT_CALL(streambuf, xsputn(data, static_cast<std::streamsize>(n)))
         .WillOnce(testing::Return(max_streamsize));
     data += n;
     size -= n;
   } while (size != 0);
-  fmt::internal::write(os, buffer);
+  fmt::detail::write_buffer(os, buffer);
 }
 
 TEST(OStreamTest, Join) {
@@ -258,7 +259,7 @@ TEST(OStreamTest, DisableBuiltinOStreamOperators) {
 struct explicitly_convertible_to_string_like {
   template <typename String,
             typename = typename std::enable_if<std::is_constructible<
-                String, const char*, std::size_t>::value>::type>
+                String, const char*, size_t>::value>::type>
   explicit operator String() const {
     return String("foo", 3u);
   }
@@ -269,13 +270,13 @@ std::ostream& operator<<(std::ostream& os,
   return os << "bar";
 }
 
-TEST(FormatterTest, FormatExplicitlyConvertibleToStringLike) {
+TEST(OStreamTest, FormatExplicitlyConvertibleToStringLike) {
   EXPECT_EQ("bar", fmt::format("{}", explicitly_convertible_to_string_like()));
 }
 
 #ifdef FMT_USE_STRING_VIEW
 struct explicitly_convertible_to_std_string_view {
-  explicit operator fmt::internal::std_string_view<char>() const {
+  explicit operator fmt::detail::std_string_view<char>() const {
     return {"foo", 3u};
   }
 };
@@ -285,8 +286,24 @@ std::ostream& operator<<(std::ostream& os,
   return os << "bar";
 }
 
-TEST(FormatterTest, FormatExplicitlyConvertibleToStdStringView) {
+TEST(OStreamTest, FormatExplicitlyConvertibleToStdStringView) {
   EXPECT_EQ("bar", fmt::format("{}", explicitly_convertible_to_string_like()));
 }
 
 #endif  // FMT_USE_STRING_VIEW
+
+struct copyfmt_test {};
+
+std::ostream& operator<<(std::ostream& os, copyfmt_test) {
+  std::ios ios(nullptr);
+  ios.copyfmt(os);
+  return os << "foo";
+}
+
+TEST(OStreamTest, CopyFmt) {
+  EXPECT_EQ("foo", fmt::format("{}", copyfmt_test()));
+}
+
+TEST(OStreamTest, CompileTimeString) {
+  EXPECT_EQ("42", fmt::format(FMT_STRING("{}"), 42));
+}
diff --git a/test/posix-mock-test.cc b/test/posix-mock-test.cc
index c4cd5530..eb85756d 100644
--- a/test/posix-mock-test.cc
+++ b/test/posix-mock-test.cc
@@ -49,8 +49,8 @@ int pipe_count;
 int fopen_count;
 int fclose_count;
 int fileno_count;
-std::size_t read_nbyte;
-std::size_t write_nbyte;
+size_t read_nbyte;
+size_t write_nbyte;
 bool sysconf_error;
 
 enum { NONE, MAX_SIZE, ERROR } fstat_sim;
@@ -261,8 +261,8 @@ TEST(FileTest, Size) {
   EXPECT_EQ(content.size(), static_cast<unsigned long long>(f.size()));
 #  ifdef _WIN32
   fmt::memory_buffer message;
-  fmt::internal::format_windows_error(message, ERROR_ACCESS_DENIED,
-                                      "cannot get file size");
+  fmt::detail::format_windows_error(message, ERROR_ACCESS_DENIED,
+                                    "cannot get file size");
   fstat_sim = ERROR;
   EXPECT_THROW_MSG(f.size(), fmt::windows_error, fmt::to_string(message));
   fstat_sim = NONE;
@@ -288,7 +288,7 @@ TEST(FileTest, ReadRetry) {
   write_end.write("test", SIZE);
   write_end.close();
   char buffer[SIZE];
-  std::size_t count = 0;
+  size_t count = 0;
   EXPECT_RETRY(count = read_end.read(buffer, SIZE), read,
                "cannot read from file");
   EXPECT_EQ_POSIX(static_cast<std::streamsize>(SIZE), count);
@@ -298,7 +298,7 @@ TEST(FileTest, WriteRetry) {
   file read_end, write_end;
   file::pipe(read_end, write_end);
   enum { SIZE = 4 };
-  std::size_t count = 0;
+  size_t count = 0;
   EXPECT_RETRY(count = write_end.write("test", SIZE), write,
                "cannot write to file");
   write_end.close();
@@ -316,8 +316,8 @@ TEST(FileTest, ConvertReadCount) {
   file read_end, write_end;
   file::pipe(read_end, write_end);
   char c;
-  std::size_t size = UINT_MAX;
-  if (sizeof(unsigned) != sizeof(std::size_t)) ++size;
+  size_t size = UINT_MAX;
+  if (sizeof(unsigned) != sizeof(size_t)) ++size;
   read_count = 1;
   read_nbyte = 0;
   EXPECT_THROW(read_end.read(&c, size), fmt::system_error);
@@ -329,8 +329,8 @@ TEST(FileTest, ConvertWriteCount) {
   file read_end, write_end;
   file::pipe(read_end, write_end);
   char c;
-  std::size_t size = UINT_MAX;
-  if (sizeof(unsigned) != sizeof(std::size_t)) ++size;
+  size_t size = UINT_MAX;
+  if (sizeof(unsigned) != sizeof(size_t)) ++size;
   write_count = 1;
   write_nbyte = 0;
   EXPECT_THROW(write_end.write(&c, size), fmt::system_error);
diff --git a/test/printf-test.cc b/test/printf-test.cc
index 5aaa27b1..ccd72dcd 100644
--- a/test/printf-test.cc
+++ b/test/printf-test.cc
@@ -17,7 +17,7 @@
 
 using fmt::format;
 using fmt::format_error;
-using fmt::internal::max_value;
+using fmt::detail::max_value;
 
 const unsigned BIG_NUM = INT_MAX + 1u;
 
@@ -113,14 +113,13 @@ TEST(PrintfTest, SwitchArgIndexing) {
 
 TEST(PrintfTest, InvalidArgIndex) {
   EXPECT_THROW_MSG(test_sprintf("%0$d", 42), format_error,
-                   "argument index out of range");
+                   "argument not found");
   EXPECT_THROW_MSG(test_sprintf("%2$d", 42), format_error,
-                   "argument index out of range");
+                   "argument not found");
   EXPECT_THROW_MSG(test_sprintf(format("%{}$d", INT_MAX), 42), format_error,
-                   "argument index out of range");
+                   "argument not found");
 
-  EXPECT_THROW_MSG(test_sprintf("%2$", 42), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(test_sprintf("%2$", 42), format_error, "argument not found");
   EXPECT_THROW_MSG(test_sprintf(format("%{}$d", BIG_NUM), 42), format_error,
                    "number is too big");
 }
@@ -140,8 +139,11 @@ TEST(PrintfTest, ZeroFlag) {
 
   EXPECT_PRINTF("+00042", "%00+6d", 42);
 
+  EXPECT_PRINTF("   42", "%05.d", 42);
+  EXPECT_PRINTF(" 0042", "%05.4d", 42);
+
   // '0' flag is ignored for non-numeric types.
-  EXPECT_PRINTF("0000x", "%05c", 'x');
+  EXPECT_PRINTF("    x", "%05c", 'x');
 }
 
 TEST(PrintfTest, PlusFlag) {
@@ -152,11 +154,38 @@ TEST(PrintfTest, PlusFlag) {
 
   // '+' flag is ignored for non-numeric types.
   EXPECT_PRINTF("x", "%+c", 'x');
+
+  // '+' flag wins over space flag
+  EXPECT_PRINTF("+42", "%+ d", 42);
+  EXPECT_PRINTF("-42", "%+ d", -42);
+  EXPECT_PRINTF("+42", "% +d", 42);
+  EXPECT_PRINTF("-42", "% +d", -42);
+  EXPECT_PRINTF("+0042", "% +05d", 42);
+  EXPECT_PRINTF("+0042", "%0+ 5d", 42);
+
+  // '+' flag and space flag are both ignored for non-numeric types.
+  EXPECT_PRINTF("x", "%+ c", 'x');
+  EXPECT_PRINTF("x", "% +c", 'x');
 }
 
 TEST(PrintfTest, MinusFlag) {
   EXPECT_PRINTF("abc  ", "%-5s", "abc");
   EXPECT_PRINTF("abc  ", "%0--5s", "abc");
+
+  EXPECT_PRINTF("7    ", "%-5d", 7);
+  EXPECT_PRINTF("97   ", "%-5hhi", 'a');
+  EXPECT_PRINTF("a    ", "%-5c", 'a');
+
+  // '0' flag is ignored if '-' flag is given
+  EXPECT_PRINTF("7    ", "%-05d", 7);
+  EXPECT_PRINTF("7    ", "%0-5d", 7);
+  EXPECT_PRINTF("a    ", "%-05c", 'a');
+  EXPECT_PRINTF("a    ", "%0-5c", 'a');
+  EXPECT_PRINTF("97   ", "%-05hhi", 'a');
+  EXPECT_PRINTF("97   ", "%0-5hhi", 'a');
+
+  // '-' and space flag don't interfere
+  EXPECT_PRINTF(" 42", "%- d", 42);
 }
 
 TEST(PrintfTest, SpaceFlag) {
@@ -222,8 +251,7 @@ TEST(PrintfTest, DynamicWidth) {
   EXPECT_EQ("42   ", test_sprintf("%*d", -5, 42));
   EXPECT_THROW_MSG(test_sprintf("%*d", 5.0, 42), format_error,
                    "width is not integer");
-  EXPECT_THROW_MSG(test_sprintf("%*d"), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(test_sprintf("%*d"), format_error, "argument not found");
   EXPECT_THROW_MSG(test_sprintf("%*d", BIG_NUM, 42), format_error,
                    "number is too big");
 }
@@ -259,6 +287,11 @@ TEST(PrintfTest, FloatPrecision) {
   EXPECT_PRINTF(buffer, "%.3a", 1234.5678);
 }
 
+TEST(PrintfTest, StringPrecision) {
+  char test[] = {'H', 'e', 'l', 'l', 'o'};
+  EXPECT_EQ(fmt::sprintf("%.4s", test), "Hell");
+}
+
 TEST(PrintfTest, IgnorePrecisionForNonNumericArg) {
   EXPECT_PRINTF("abc", "%.5s", "abc");
 }
@@ -268,8 +301,7 @@ TEST(PrintfTest, DynamicPrecision) {
   EXPECT_EQ("42", test_sprintf("%.*d", -5, 42));
   EXPECT_THROW_MSG(test_sprintf("%.*d", 5.0, 42), format_error,
                    "precision is not integer");
-  EXPECT_THROW_MSG(test_sprintf("%.*d"), format_error,
-                   "argument index out of range");
+  EXPECT_THROW_MSG(test_sprintf("%.*d"), format_error, "argument not found");
   EXPECT_THROW_MSG(test_sprintf("%.*d", BIG_NUM, 42), format_error,
                    "number is too big");
   if (sizeof(long long) != sizeof(int)) {
@@ -298,7 +330,7 @@ void TestLength(const char* length_spec, U value) {
   unsigned long long unsigned_value = 0;
   // Apply integer promotion to the argument.
   unsigned long long max = max_value<U>();
-  using fmt::internal::const_check;
+  using fmt::detail::const_check;
   if (const_check(max <= static_cast<unsigned>(max_value<int>()))) {
     signed_value = static_cast<int>(value);
     unsigned_value = static_cast<unsigned long long>(value);
@@ -367,7 +399,7 @@ TEST(PrintfTest, Length) {
   TestLength<long long>("ll");
   TestLength<unsigned long long>("ll");
   TestLength<intmax_t>("j");
-  TestLength<std::size_t>("z");
+  TestLength<size_t>("z");
   TestLength<std::ptrdiff_t>("t");
   long double max = max_value<long double>();
   EXPECT_PRINTF(fmt::format("{:.6}", max), "%g", max);
@@ -447,6 +479,12 @@ TEST(PrintfTest, String) {
   EXPECT_PRINTF(L"    (null)", L"%10s", null_wstr);
 }
 
+TEST(PrintfTest, UCharString) {
+  unsigned char str[] = "test";
+  unsigned char* pstr = str;
+  EXPECT_EQ("test", fmt::sprintf("%s", pstr));
+}
+
 TEST(PrintfTest, Pointer) {
   int n;
   void* p = &n;
@@ -502,9 +540,7 @@ TEST(PrintfTest, PrintfError) {
 TEST(PrintfTest, WideString) { EXPECT_EQ(L"abc", fmt::sprintf(L"%s", L"abc")); }
 
 TEST(PrintfTest, PrintfCustom) {
-  // The test is disabled for now because it requires decoupling
-  // fallback_formatter::format from format_context.
-  //EXPECT_EQ("abc", test_sprintf("%s", TestString("abc")));
+  EXPECT_EQ("abc", test_sprintf("%s", TestString("abc")));
 }
 
 TEST(PrintfTest, OStream) {
@@ -571,51 +607,22 @@ TEST(PrintfTest, VSPrintfMakeWArgsExample) {
 #endif
 }
 
-typedef fmt::printf_arg_formatter<fmt::buffer_range<char>> formatter_t;
-typedef fmt::basic_printf_context<formatter_t::iterator, char> context_t;
+TEST(PrintfTest, PrintfDetermineOutputSize) {
+  using backit = std::back_insert_iterator<std::vector<char>>;
+  using truncated_printf_context =
+      fmt::basic_printf_context<fmt::detail::truncating_iterator<backit>, char>;
 
-// A custom printf argument formatter that doesn't print `-` for floating-point
-// values rounded to 0.
-class custom_printf_arg_formatter : public formatter_t {
- public:
-  using formatter_t::iterator;
+  auto v = std::vector<char>{};
+  auto it = std::back_inserter(v);
 
-  custom_printf_arg_formatter(formatter_t::iterator iter,
-                              formatter_t::format_specs& specs, context_t& ctx)
-      : formatter_t(iter, specs, ctx) {}
+  const auto format_string = "%s";
+  const auto format_arg = "Hello";
+  const auto expected_size = fmt::sprintf(format_string, format_arg).size();
 
-  using formatter_t::operator();
-
-#if FMT_MSC_VER > 0 && FMT_MSC_VER <= 1804
-  template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
-  iterator operator()(T value){
-#else
-  iterator operator()(double value) {
-#endif
-      // Comparing a float to 0.0 is safe.
-      if (round(value * pow(10, specs()->precision)) == 0.0) value = 0;
-  return formatter_t::operator()(value);
-}
-}
-;
-
-typedef fmt::basic_format_args<context_t> format_args_t;
-
-std::string custom_vformat(fmt::string_view format_str, format_args_t args) {
-  fmt::memory_buffer buffer;
-  fmt::vprintf<custom_printf_arg_formatter>(buffer, format_str, args);
-  return std::string(buffer.data(), buffer.size());
-}
-
-template <typename... Args>
-std::string custom_format(const char* format_str, const Args&... args) {
-  auto va = fmt::make_printf_args(args...);
-  return custom_vformat(format_str, {va});
-}
-
-TEST(PrintfTest, CustomFormat) {
-  EXPECT_EQ("0.00", custom_format("%.2f", -.00001));
-  EXPECT_EQ("0.00", custom_format("%.2f", .00001));
-  EXPECT_EQ("1.00", custom_format("%.2f", 1.00001));
-  EXPECT_EQ("-1.00", custom_format("%.2f", -1.00001));
+  EXPECT_EQ((truncated_printf_context(
+                 fmt::detail::truncating_iterator<backit>(it, 0), format_string,
+                 fmt::make_format_args<truncated_printf_context>(format_arg))
+                 .format()
+                 .count()),
+            expected_size);
 }
diff --git a/test/ranges-test.cc b/test/ranges-test.cc
index a729948d..46208e8d 100644
--- a/test/ranges-test.cc
+++ b/test/ranges-test.cc
@@ -79,7 +79,7 @@ TEST(RangesTest, JoinInitializerList) {
 struct my_struct {
   int32_t i;
   std::string str;  // can throw
-  template <std::size_t N> decltype(auto) get() const noexcept {
+  template <size_t N> decltype(auto) get() const noexcept {
     if constexpr (N == 0)
       return i;
     else if constexpr (N == 1)
@@ -87,16 +87,15 @@ struct my_struct {
   }
 };
 
-template <std::size_t N> decltype(auto) get(const my_struct& s) noexcept {
+template <size_t N> decltype(auto) get(const my_struct& s) noexcept {
   return s.get<N>();
 }
 
 namespace std {
 
-template <>
-struct tuple_size<my_struct> : std::integral_constant<std::size_t, 2> {};
+template <> struct tuple_size<my_struct> : std::integral_constant<size_t, 2> {};
 
-template <std::size_t N> struct tuple_element<N, my_struct> {
+template <size_t N> struct tuple_element<N, my_struct> {
   using type = decltype(std::declval<my_struct>().get<N>());
 };
 
@@ -140,3 +139,17 @@ TEST(RangesTest, FormatStringLike) {
   EXPECT_EQ("foo", fmt::format("{}", string_like()));
 }
 #endif  // FMT_USE_STRING_VIEW
+
+struct zstring_sentinel {};
+bool operator==(const char* p, zstring_sentinel) { return *p == '\0'; }
+bool operator!=(const char* p, zstring_sentinel) { return *p != '\0'; }
+struct zstring {
+  const char* p;
+  const char* begin() const { return p; }
+  zstring_sentinel end() const { return {}; }
+};
+TEST(RangesTest, JoinSentinel) {
+  zstring hello{"hello"};
+  EXPECT_EQ("{'h', 'e', 'l', 'l', 'o'}", fmt::format("{}", hello));
+  EXPECT_EQ("h_e_l_l_o", fmt::format("{}", fmt::join(hello, "_")));
+}
diff --git a/test/scan-test.cc b/test/scan-test.cc
index 0b49fd9f..962de54c 100644
--- a/test/scan-test.cc
+++ b/test/scan-test.cc
@@ -5,12 +5,14 @@
 //
 // For the license information refer to format.h.
 
+#include "scan.h"
+
 #include <time.h>
+
 #include <climits>
 
 #include "gmock.h"
 #include "gtest-extra.h"
-#include "scan.h"
 
 TEST(ScanTest, ReadText) {
   fmt::string_view s = "foo";
@@ -73,7 +75,7 @@ template <> struct scanner<tm> {
     if (it != ctx.end() && *it == ':') ++it;
     auto end = it;
     while (end != ctx.end() && *end != '}') ++end;
-    format.reserve(internal::to_unsigned(end - it + 1));
+    format.reserve(detail::to_unsigned(end - it + 1));
     format.append(it, end);
     format.push_back('\0');
     return end;
diff --git a/test/scan.h b/test/scan.h
index af421bce..de82067a 100644
--- a/test/scan.h
+++ b/test/scan.h
@@ -31,7 +31,7 @@ class scan_parse_context {
   FMT_CONSTEXPR iterator end() const { return format_.end(); }
 
   void advance_to(iterator it) {
-    format_.remove_prefix(internal::to_unsigned(it - begin()));
+    format_.remove_prefix(detail::to_unsigned(it - begin()));
   }
 };
 
@@ -48,11 +48,11 @@ struct scan_context {
   iterator end() const { return begin() + input_.size(); }
 
   void advance_to(iterator it) {
-    input_.remove_prefix(internal::to_unsigned(it - begin()));
+    input_.remove_prefix(detail::to_unsigned(it - begin()));
   }
 };
 
-namespace internal {
+namespace detail {
 enum class scan_type {
   none_type,
   int_type,
@@ -107,20 +107,20 @@ class scan_arg {
     ctx.advance_to(s.scan(*static_cast<T*>(arg), ctx));
   }
 };
-}  // namespace internal
+}  // namespace detail
 
 struct scan_args {
   int size;
-  const internal::scan_arg* data;
+  const detail::scan_arg* data;
 
   template <size_t N>
-  scan_args(const std::array<internal::scan_arg, N>& store)
+  scan_args(const std::array<detail::scan_arg, N>& store)
       : size(N), data(store.data()) {
     static_assert(N < INT_MAX, "too many arguments");
   }
 };
 
-namespace internal {
+namespace detail {
 
 struct scan_handler : error_handler {
  private:
@@ -169,14 +169,15 @@ struct scan_handler : error_handler {
     scan_ctx_.advance_to(it + size);
   }
 
-  void on_arg_id() { on_arg_id(next_arg_id_++); }
-  void on_arg_id(int id) {
+  int on_arg_id() { return on_arg_id(next_arg_id_++); }
+  int on_arg_id(int id) {
     if (id >= args_.size) on_error("argument index out of range");
     arg_ = args_.data[id];
+    return id;
   }
-  void on_arg_id(string_view) { on_error("invalid format"); }
+  int on_arg_id(string_view) { return on_error("invalid format"), 0; }
 
-  void on_replacement_field(const char*) {
+  void on_replacement_field(int, const char*) {
     auto it = scan_ctx_.begin(), end = scan_ctx_.end();
     switch (arg_.type) {
     case scan_type::int_type:
@@ -208,24 +209,24 @@ struct scan_handler : error_handler {
     }
   }
 
-  const char* on_format_specs(const char* begin, const char*) {
+  const char* on_format_specs(int, const char* begin, const char*) {
     if (arg_.type != scan_type::custom_type) return begin;
     parse_ctx_.advance_to(begin);
     arg_.custom.scan(arg_.custom.value, parse_ctx_, scan_ctx_);
     return parse_ctx_.begin();
   }
 };
-}  // namespace internal
+}  // namespace detail
 
 template <typename... Args>
-std::array<internal::scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
+std::array<detail::scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
   return {{args...}};
 }
 
 string_view::iterator vscan(string_view input, string_view format_str,
                             scan_args args) {
-  internal::scan_handler h(format_str, input, args);
-  internal::parse_format_string<false>(format_str, h);
+  detail::scan_handler h(format_str, input, args);
+  detail::parse_format_string<false>(format_str, h);
   return input.begin() + (h.pos() - &*input.begin());
 }
 
diff --git a/test/std-format-test.cc b/test/std-format-test.cc
index 36cbdd10..8bf4b6d1 100644
--- a/test/std-format-test.cc
+++ b/test/std-format-test.cc
@@ -1,4 +1,5 @@
 #include <format>
+
 #include "gtest.h"
 
 TEST(StdFormatTest, Escaping) {
@@ -61,7 +62,7 @@ TEST(StdFormatTest, Int) {
   string s0 = format("{}", 42);                       // s0 == "42"
   string s1 = format("{0:b} {0:d} {0:o} {0:x}", 42);  // s1 == "101010 42 52 2a"
   string s2 = format("{0:#x} {0:#X}", 42);            // s2 == "0x2a 0X2A"
-  string s3 = format("{:n}", 1234);  // s3 == "1234" (depends on the locale)
+  string s3 = format("{:L}", 1234);  // s3 == "1234" (depends on the locale)
   EXPECT_EQ(s0, "42");
   EXPECT_EQ(s1, "101010 42 52 2a");
   EXPECT_EQ(s2, "0x2a 0X2A");
@@ -123,7 +124,7 @@ template <> struct std::formatter<S> {
           if constexpr (!is_integral_v<type> || is_same_v<type, bool>)
             throw format_error("width is not integral");
           // else if (value < 0 || value > numeric_limits<int>::max())
-          else if (fmt::internal::is_negative(value) ||
+          else if (fmt::detail::is_negative(value) ||
                    value > numeric_limits<int>::max())
             throw format_error("invalid width");
           else
diff --git a/test/test-assert.h b/test/test-assert.h
index c02dc0f2..f613722f 100644
--- a/test/test-assert.h
+++ b/test/test-assert.h
@@ -9,6 +9,7 @@
 #define FMT_TEST_ASSERT_H_
 
 #include <stdexcept>
+
 #include "gtest.h"
 
 class assertion_failure : public std::logic_error {
diff --git a/test/test-main.cc b/test/test-main.cc
index d911131f..8db257d6 100644
--- a/test/test-main.cc
+++ b/test/test-main.cc
@@ -6,6 +6,7 @@
 // For the license information refer to format.h.
 
 #include <cstdlib>
+
 #include "gtest.h"
 
 #ifdef _WIN32
diff --git a/test/util.cc b/test/util.cc
index e75bd450..d08dcbdc 100644
--- a/test/util.cc
+++ b/test/util.cc
@@ -6,6 +6,7 @@
 // For the license information refer to format.h.
 
 #include "util.h"
+
 #include <cstring>
 
 void increment(char* s) {
diff --git a/test/util.h b/test/util.h
index 2282886a..24a5f4e3 100644
--- a/test/util.h
+++ b/test/util.h
@@ -19,7 +19,7 @@ enum { BUFFER_SIZE = 256 };
 #  define FMT_VSNPRINTF vsnprintf
 #endif
 
-template <std::size_t SIZE>
+template <size_t SIZE>
 void safe_sprintf(char (&buffer)[SIZE], const char* format, ...) {
   std::va_list args;
   va_start(args, format);