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+Ninja Multi-Config
+------------------
+
+Generates multiple ``build-<Config>.ninja`` files.
+
+This generator is very much like the :generator:`Ninja` generator, but with
+some key differences. Only these differences will be discussed in this
+document.
+
+Unlike the :generator:`Ninja` generator, ``Ninja Multi-Config`` generates
+multiple configurations at once with :variable:`CMAKE_CONFIGURATION_TYPES`
+instead of only one configuration with :variable:`CMAKE_BUILD_TYPE`. One
+``build-<Config>.ninja`` file will be generated for each of these
+configurations (with ``<Config>`` being the configuration name.) These files
+are intended to be run with ``ninja -f build-<Config>.ninja``. A
+``build.ninja`` file is also generated, using the configuration from either
+:variable:`CMAKE_DEFAULT_BUILD_TYPE` or the first item from
+:variable:`CMAKE_CONFIGURATION_TYPES`.
+
+``cmake --build . --config <Config>`` will always use ``build-<Config>.ninja``
+to build. If no ``--config`` argument is specified, ``cmake --build .`` will
+default to ``build-Debug.ninja``, unless a ``build.ninja`` is generated (see
+below), in which case that will be used instead.
+
+Each ``build-<Config>.ninja`` file contains ``<target>`` targets as well as
+``<target>:<Config>`` targets, where ``<Config>`` is the same as the
+configuration specified in ``build-<Config>.ninja`` Additionally, if
+cross-config mode is enabled, ``build-<Config>.ninja`` may contain
+``<target>:<OtherConfig>`` targets, where ``<OtherConfig>`` is a cross-config,
+as well as ``<target>:all``, which builds the target in all cross-configs. See
+below for how to enable cross-config mode.
+
+The ``Ninja Multi-Config`` generator recognizes the following variables:
+
+:variable:`CMAKE_CONFIGURATION_TYPES`
+  Specifies the total set of configurations to build.
+
+:variable:`CMAKE_CROSS_CONFIGS`
+  Specifies a :ref:`semicolon-separated list <CMake Language Lists>` of
+  configurations available from all ``build-<Config>.ninja`` files.
+
+:variable:`CMAKE_DEFAULT_BUILD_TYPE`
+  Specifies the configuration to use by default in a ``build.ninja`` file.
+
+:variable:`CMAKE_DEFAULT_CONFIGS`
+  Specifies a :ref:`semicolon-separated list <CMake Language Lists>` of
+  configurations to build for a target in ``build.ninja``
+  if no ``:<Config>`` suffix is specified.
+
+Consider the following example:
+
+.. code-block:: cmake
+
+  cmake_minimum_required(VERSION 3.16)
+  project(MultiConfigNinja C)
+
+  add_executable(generator generator.c)
+  add_custom_command(OUTPUT generated.c COMMAND generator generated.c)
+  add_library(generated ${CMAKE_BINARY_DIR}/generated.c)
+
+Now assume you configure the project with ``Ninja Multi-Config`` and run one of
+the following commands:
+
+.. code-block:: shell
+
+  ninja -f build-Debug.ninja generated
+  # OR
+  cmake --build . --config Debug --target generated
+
+This would build the ``Debug`` configuration of ``generator``, which would be
+used to generate ``generated.c``, which would be used to build the ``Debug``
+configuration of ``generated``.
+
+But if :variable:`CMAKE_CROSS_CONFIGS` is set to ``all``, and you run the
+following instead:
+
+.. code-block:: shell
+
+  ninja -f build-Release.ninja generated:Debug
+  # OR
+  cmake --build . --config Release --target generated:Debug
+
+This would build the ``Release`` configuration of ``generator``, which would be
+used to generate ``generated.c``, which would be used to build the ``Debug``
+configuration of ``generated``. This is useful for running a release-optimized
+version of a generator utility while still building the debug version of the
+targets built with the generated code.