diff --git a/include/fmt/core.h b/include/fmt/core.h
index d6c941fa1271..9c90e6398d47 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -1099,6 +1099,7 @@ FMT_CONSTEXPR void basic_format_parse_context<Char>::check_dynamic_spec(
 
 FMT_EXPORT template <typename Context> class basic_format_arg;
 FMT_EXPORT template <typename Context> class basic_format_args;
+FMT_EXPORT template <typename Context, typename... Args> class format_arg_store;
 FMT_EXPORT template <typename Context> class dynamic_format_arg_store;
 
 // A formatter for objects of type T.
@@ -1129,7 +1130,7 @@ template <typename T> class basic_appender {
   using difference_type = ptrdiff_t;
   FMT_UNCHECKED_ITERATOR(basic_appender);
 
-  basic_appender(detail::buffer<T>& buf) : buffer_(&buf) {}
+  FMT_CONSTEXPR basic_appender(detail::buffer<T>& buf) : buffer_(&buf) {}
 
   auto operator=(T c) -> basic_appender& {
     buffer_->push_back(c);
@@ -1733,147 +1734,6 @@ FMT_DEPRECATED FMT_CONSTEXPR FMT_INLINE auto visit_format_arg(
   return arg.visit(static_cast<Visitor&&>(vis));
 }
 
-// Formatting context.
-template <typename OutputIt, typename Char> class basic_format_context {
- private:
-  OutputIt out_;
-  basic_format_args<basic_format_context> args_;
-  detail::locale_ref loc_;
-
- public:
-  using iterator = OutputIt;
-  using format_arg = basic_format_arg<basic_format_context>;
-  using format_args = basic_format_args<basic_format_context>;
-  using parse_context_type = basic_format_parse_context<Char>;
-  template <typename T> using formatter_type = formatter<T, Char>;
-
-  /** The character type for the output. */
-  using char_type = Char;
-
-  basic_format_context(basic_format_context&&) = default;
-  basic_format_context(const basic_format_context&) = delete;
-  void operator=(const basic_format_context&) = delete;
-  /**
-    Constructs a ``basic_format_context`` object. References to the arguments
-    are stored in the object so make sure they have appropriate lifetimes.
-   */
-  constexpr basic_format_context(OutputIt out, format_args ctx_args,
-                                 detail::locale_ref loc = {})
-      : out_(out), args_(ctx_args), loc_(loc) {}
-
-  constexpr auto arg(int id) const -> format_arg { return args_.get(id); }
-  FMT_CONSTEXPR auto arg(basic_string_view<Char> name) -> format_arg {
-    return args_.get(name);
-  }
-  FMT_CONSTEXPR auto arg_id(basic_string_view<Char> name) -> int {
-    return args_.get_id(name);
-  }
-  auto args() const -> const format_args& { return args_; }
-
-  // This function is intentionally not constexpr to give a compile-time error.
-  void on_error(const char* message) { throw_format_error(message); }
-
-  // Returns an iterator to the beginning of the output range.
-  FMT_CONSTEXPR auto out() -> iterator { return out_; }
-
-  // Advances the begin iterator to ``it``.
-  void advance_to(iterator it) {
-    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
-  }
-
-  FMT_CONSTEXPR auto locale() -> detail::locale_ref { return loc_; }
-};
-
-template <typename Char>
-using buffer_context = basic_format_context<basic_appender<Char>, Char>;
-using format_context = basic_format_context<appender, char>;
-
-template <typename T, typename Char = char>
-using is_formattable = bool_constant<!std::is_base_of<
-    detail::unformattable, decltype(detail::arg_mapper<buffer_context<Char>>()
-                                        .map(std::declval<T&>()))>::value>;
-
-/**
-  \rst
-  An array of references to arguments. It can be implicitly converted into
-  `~fmt::basic_format_args` for passing into type-erased formatting functions
-  such as `~fmt::vformat`.
-  \endrst
- */
-template <typename Context, typename... Args>
-class format_arg_store
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
-    // Workaround a GCC template argument substitution bug.
-    : public basic_format_args<Context>
-#endif
-{
- private:
-  static const size_t num_args = sizeof...(Args);
-  static constexpr 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, detail::value<Context>,
-                                   basic_format_arg<Context>>;
-
-  detail::arg_data<value_type, typename Context::char_type, num_args,
-                   num_named_args>
-      data_;
-
-  friend class basic_format_args<Context>;
-
-  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:
-  template <typename... T>
-  FMT_CONSTEXPR FMT_INLINE format_arg_store(T&... args)
-      :
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
-        basic_format_args<Context>(*this),
-#endif
-        data_{detail::make_arg<is_packed, Context>(args)...} {
-    if (detail::const_check(num_named_args != 0))
-      detail::init_named_args(data_.named_args(), 0, 0, args...);
-  }
-};
-
-/**
-  \rst
-  Constructs a `~fmt::format_arg_store` object that contains references to
-  arguments and can be implicitly converted to `~fmt::format_args`. `Context`
-  can be omitted in which case it defaults to `~fmt::format_context`.
-  See `~fmt::arg` for lifetime considerations.
-  \endrst
- */
-// Arguments are taken by lvalue references to avoid some lifetime issues.
-template <typename Context = format_context, typename... T>
-constexpr auto make_format_args(T&... args)
-    -> format_arg_store<Context, remove_const_t<T>...> {
-  return {args...};
-}
-
-/**
-  \rst
-  Returns a named argument to be used in a formatting function.
-  It should only be used in a call to a formatting function or
-  `dynamic_format_arg_store::push_back`.
-
-  **Example**::
-
-    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
-  \endrst
- */
-template <typename Char, typename T>
-inline auto arg(const Char* name, const T& arg) -> detail::named_arg<Char, T> {
-  static_assert(!detail::is_named_arg<T>(), "nested named arguments");
-  return {name, arg};
-}
-FMT_END_EXPORT
-
 /**
   \rst
   A view of a collection of formatting arguments. To avoid lifetime issues it
@@ -1908,7 +1768,7 @@ template <typename Context> class basic_format_args {
   constexpr auto is_packed() const -> bool {
     return (desc_ & detail::is_unpacked_bit) == 0;
   }
-  auto has_named_args() const -> bool {
+  constexpr auto has_named_args() const -> bool {
     return (desc_ & detail::has_named_args_bit) != 0;
   }
 
@@ -1978,7 +1838,7 @@ template <typename Context> class basic_format_args {
   }
 
   template <typename Char>
-  auto get_id(basic_string_view<Char> name) const -> int {
+  FMT_CONSTEXPR auto get_id(basic_string_view<Char> name) const -> int {
     if (!has_named_args()) return -1;
     const auto& named_args =
         (is_packed() ? values_[-1] : args_[-1].value_).named_args;
@@ -1995,6 +1855,151 @@ template <typename Context> class basic_format_args {
   }
 };
 
+// A formatting context.
+class context {
+ private:
+  appender out_;
+  basic_format_args<context> args_;
+  detail::locale_ref loc_;
+
+ public:
+  /** The character type for the output. */
+  using char_type = char;
+
+  using iterator = appender;
+  using format_arg = basic_format_arg<context>;
+  using format_args = basic_format_args<context>;
+  using parse_context_type = basic_format_parse_context<char>;
+  template <typename T> using formatter_type = formatter<T, char>;
+
+  /**
+    Constructs a ``basic_format_context`` object. References to the arguments
+    are stored in the object so make sure they have appropriate lifetimes.
+   */
+  FMT_CONSTEXPR context(iterator out, format_args ctx_args,
+                        detail::locale_ref loc = {})
+      : out_(out), args_(ctx_args), loc_(loc) {}
+  context(context&&) = default;
+  context(const context&) = delete;
+  void operator=(const context&) = delete;
+
+  FMT_CONSTEXPR auto arg(int id) const -> format_arg { return args_.get(id); }
+  auto arg(string_view name) -> format_arg { return args_.get(name); }
+  FMT_CONSTEXPR auto arg_id(string_view name) -> int {
+    return args_.get_id(name);
+  }
+  auto args() const -> const format_args& { return args_; }
+
+  // This function is intentionally not constexpr to give a compile-time error.
+  void on_error(const char* message) { throw_format_error(message); }
+
+  // Returns an iterator to the beginning of the output range.
+  FMT_CONSTEXPR auto out() -> iterator { return out_; }
+
+  // Advances the begin iterator to ``it``.
+  void advance_to(iterator) {}
+
+  FMT_CONSTEXPR auto locale() -> detail::locale_ref { return loc_; }
+};
+
+template <typename OutputIt, typename Char> class generic_context;
+
+// Longer aliases for C++20 compatibility.
+template <typename OutputIt, typename Char>
+using basic_format_context =
+    conditional_t<std::is_same<OutputIt, appender>::value, context,
+                  generic_context<OutputIt, Char>>;
+using format_context = context;
+
+template <typename Char>
+using buffer_context = basic_format_context<basic_appender<Char>, Char>;
+
+template <typename T, typename Char = char>
+using is_formattable = bool_constant<!std::is_base_of<
+    detail::unformattable, decltype(detail::arg_mapper<buffer_context<Char>>()
+                                        .map(std::declval<T&>()))>::value>;
+
+/**
+  \rst
+  An array of references to arguments. It can be implicitly converted into
+  `~fmt::basic_format_args` for passing into type-erased formatting functions
+  such as `~fmt::vformat`.
+  \endrst
+ */
+template <typename Context, typename... Args>
+class format_arg_store
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+    // Workaround a GCC template argument substitution bug.
+    : public basic_format_args<Context>
+#endif
+{
+ private:
+  static const size_t num_args = sizeof...(Args);
+  static constexpr 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, detail::value<Context>,
+                                   basic_format_arg<Context>>;
+
+  detail::arg_data<value_type, typename Context::char_type, num_args,
+                   num_named_args>
+      data_;
+
+  friend class basic_format_args<Context>;
+
+  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:
+  template <typename... T>
+  FMT_CONSTEXPR FMT_INLINE format_arg_store(T&... args)
+      :
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+        basic_format_args<Context>(*this),
+#endif
+        data_{detail::make_arg<is_packed, Context>(args)...} {
+    if (detail::const_check(num_named_args != 0))
+      detail::init_named_args(data_.named_args(), 0, 0, args...);
+  }
+};
+
+/**
+  \rst
+  Constructs a `~fmt::format_arg_store` object that contains references to
+  arguments and can be implicitly converted to `~fmt::format_args`. `Context`
+  can be omitted in which case it defaults to `~fmt::format_context`.
+  See `~fmt::arg` for lifetime considerations.
+  \endrst
+ */
+// Arguments are taken by lvalue references to avoid some lifetime issues.
+template <typename Context = format_context, typename... T>
+constexpr auto make_format_args(T&... args)
+    -> format_arg_store<Context, remove_const_t<T>...> {
+  return {args...};
+}
+
+/**
+  \rst
+  Returns a named argument to be used in a formatting function.
+  It should only be used in a call to a formatting function or
+  `dynamic_format_arg_store::push_back`.
+
+  **Example**::
+
+    fmt::print("Elapsed time: {s:.2f} seconds", fmt::arg("s", 1.23));
+  \endrst
+ */
+template <typename Char, typename T>
+inline auto arg(const Char* name, const T& arg) -> detail::named_arg<Char, T> {
+  static_assert(!detail::is_named_arg<T>(), "nested named arguments");
+  return {name, arg};
+}
+FMT_END_EXPORT
+
 /** An alias to ``basic_format_args<format_context>``. */
 // A separate type would result in shorter symbols but break ABI compatibility
 // between clang and gcc on ARM (#1919).
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 282aeae1b915..9b74a89d2f88 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1071,6 +1071,50 @@ constexpr auto compile_string_to_view(detail::std_string_view<Char> s)
 }
 }  // namespace detail_exported
 
+// A generic formatting context with custom output iterator and character
+// (code unit) support.
+template <typename OutputIt, typename Char> class generic_context {
+ private:
+  OutputIt out_;
+  basic_format_args<generic_context> args_;
+  detail::locale_ref loc_;
+
+ public:
+  using char_type = Char;
+  using iterator = OutputIt;
+  using format_args = basic_format_args<generic_context>;
+  using parse_context_type = basic_format_parse_context<Char>;
+  template <typename T> using formatter_type = formatter<T, Char>;
+
+  constexpr generic_context(OutputIt out, format_args ctx_args,
+                            detail::locale_ref loc = {})
+      : out_(out), args_(ctx_args), loc_(loc) {}
+  generic_context(generic_context&&) = default;
+  generic_context(const generic_context&) = delete;
+  void operator=(const generic_context&) = delete;
+
+  constexpr auto arg(int id) const -> basic_format_arg<generic_context> {
+    return args_.get(id);
+  }
+  auto arg(basic_string_view<Char> name) -> basic_format_arg<generic_context> {
+    return args_.get(name);
+  }
+  FMT_CONSTEXPR auto arg_id(basic_string_view<Char> name) -> int {
+    return args_.get_id(name);
+  }
+  auto args() const -> const format_args& { return args_; }
+
+  void on_error(const char* message) { throw_format_error(message); }
+
+  FMT_CONSTEXPR auto out() -> iterator { return out_; }
+
+  void advance_to(iterator it) {
+    if (!detail::is_back_insert_iterator<iterator>()) out_ = it;
+  }
+
+  FMT_CONSTEXPR auto locale() -> detail::locale_ref { return loc_; }
+};
+
 class loc_value {
  private:
   basic_format_arg<format_context> value_;
diff --git a/include/fmt/ostream.h b/include/fmt/ostream.h
index 26fb3b5ac071..9906e5f22c73 100644
--- a/include/fmt/ostream.h
+++ b/include/fmt/ostream.h
@@ -143,9 +143,8 @@ template <typename Char>
 struct basic_ostream_formatter : formatter<basic_string_view<Char>, Char> {
   void set_debug_format() = delete;
 
-  template <typename T, typename OutputIt>
-  auto format(const T& value, basic_format_context<OutputIt, Char>& ctx) const
-      -> OutputIt {
+  template <typename T, typename Context>
+  auto format(const T& value, Context& ctx) const -> decltype(ctx.out()) {
     auto buffer = basic_memory_buffer<Char>();
     detail::format_value(buffer, value);
     return formatter<basic_string_view<Char>, Char>::format(
@@ -158,9 +157,9 @@ using ostream_formatter = basic_ostream_formatter<char>;
 template <typename T, typename Char>
 struct formatter<detail::streamed_view<T>, Char>
     : basic_ostream_formatter<Char> {
-  template <typename OutputIt>
-  auto format(detail::streamed_view<T> view,
-              basic_format_context<OutputIt, Char>& ctx) const -> OutputIt {
+  template <typename Context>
+  auto format(detail::streamed_view<T> view, Context& ctx) const
+      -> decltype(ctx.out()) {
     return basic_ostream_formatter<Char>::format(view.value, ctx);
   }
 };
diff --git a/include/fmt/std.h b/include/fmt/std.h
index 885176c0fdae..d8f30a192d67 100644
--- a/include/fmt/std.h
+++ b/include/fmt/std.h
@@ -400,9 +400,9 @@ struct formatter<
     return it;
   }
 
-  template <typename OutputIt>
-  auto format(const std::exception& ex,
-              basic_format_context<OutputIt, Char>& ctx) const -> OutputIt {
+  template <typename Context>
+  auto format(const std::exception& ex, Context& ctx) const
+      -> decltype(ctx.out()) {
     format_specs<Char> spec;
     auto out = ctx.out();
     if (!with_typename_)
diff --git a/test/core-test.cc b/test/core-test.cc
index 3ebe3ee7a971..4a96ccda9a03 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -368,7 +368,7 @@ VISIT_TYPE(unsigned long, unsigned long long);
   {                                                                       \
     testing::StrictMock<mock_visitor<decltype(expected)>> visitor;        \
     EXPECT_CALL(visitor, visit(expected));                                \
-    using iterator = std::back_insert_iterator<buffer<Char>>;             \
+    using iterator = fmt::basic_appender<Char>;                           \
     auto var = value;                                                     \
     fmt::detail::make_arg<fmt::basic_format_context<iterator, Char>>(var) \
         .visit(visitor);                                                  \
@@ -379,7 +379,6 @@ VISIT_TYPE(unsigned long, unsigned long long);
     using value_type = decltype(value);                     \
     typename visit_type<value_type>::type expected = value; \
     CHECK_ARG(char, expected, value)                        \
-    CHECK_ARG(wchar_t, expected, value)                     \
   }
 
 template <typename T> class numeric_arg_test : public testing::Test {};
@@ -419,23 +418,10 @@ TEST(arg_test, string_arg) {
   CHECK_ARG(char, sv, std::string(str));
 }
 
-TEST(arg_test, wstring_arg) {
-  wchar_t str_data[] = L"test";
-  wchar_t* str = str_data;
-  const wchar_t* cstr = str;
-
-  auto sv = fmt::basic_string_view<wchar_t>(str);
-  CHECK_ARG(wchar_t, cstr, str);
-  CHECK_ARG(wchar_t, cstr, cstr);
-  CHECK_ARG(wchar_t, sv, std::wstring(str));
-  CHECK_ARG(wchar_t, sv, fmt::basic_string_view<wchar_t>(str));
-}
-
 TEST(arg_test, pointer_arg) {
   void* p = nullptr;
   const void* cp = nullptr;
   CHECK_ARG(char, cp, p);
-  CHECK_ARG(wchar_t, cp, p);
   CHECK_ARG_SIMPLE(cp);
 }