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integration/cmake.md
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# CMake
## Integration
You can use the `nlohmann_json::nlohmann_json` interface target in CMake. This target populates the appropriate usage
requirements for [`INTERFACE_INCLUDE_DIRECTORIES`](https://cmake.org/cmake/help/latest/prop_tgt/INTERFACE_INCLUDE_DIRECTORIES.html)
to point to the appropriate include directories and [`INTERFACE_COMPILE_FEATURES`](https://cmake.org/cmake/help/latest/prop_tgt/INTERFACE_COMPILE_FEATURES.html)
for the necessary C++11 flags.
### External
To use this library from a CMake project, you can locate it directly with [`find_package()`](https://cmake.org/cmake/help/latest/command/find_package.html)
and use the namespaced imported target from the generated package configuration:
!!! example
```cmake title="CMakeLists.txt"
cmake_minimum_required(VERSION 3.5)
project(ExampleProject LANGUAGES CXX)
find_package(nlohmann_json 3.12.0 REQUIRED)
add_executable(example example.cpp)
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
The package configuration file, `nlohmann_jsonConfig.cmake`, can be used either from an install tree or directly out of
the build tree.
### Embedded
To embed the library directly into an existing CMake project, place the entire source tree in a subdirectory and call
`add_subdirectory()` in your `CMakeLists.txt` file.
!!! example
```cmake title="CMakeLists.txt"
cmake_minimum_required(VERSION 3.5)
project(ExampleProject LANGUAGES CXX)
# If you only include this third party in PRIVATE source files, you do not need to install it
# when your main project gets installed.
set(JSON_Install OFF CACHE INTERNAL "")
add_subdirectory(nlohmann_json)
add_executable(example example.cpp)
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
!!! note
Do not use `#!cmake include(nlohmann_json/CMakeLists.txt)`, since that carries with it unintended consequences that
will break the build. It is generally discouraged (although not necessarily well documented as such) to use
`#!cmake include(...)` for pulling in other CMake projects anyways.
### Supporting Both
To allow your project to support either an externally supplied or an embedded JSON library, you can use a pattern akin
to the following.
!!! example
```cmake title="CMakeLists.txt"
project(ExampleProject LANGUAGES CXX)
option(EXAMPLE_USE_EXTERNAL_JSON "Use an external JSON library" OFF)
add_subdirectory(thirdparty)
add_executable(example example.cpp)
# Note that the namespaced target will always be available regardless of the import method
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
```cmake title="thirdparty/CMakeLists.txt"
if(EXAMPLE_USE_EXTERNAL_JSON)
find_package(nlohmann_json 3.12.0 REQUIRED)
else()
set(JSON_BuildTests OFF CACHE INTERNAL "")
add_subdirectory(nlohmann_json)
endif()
```
`thirdparty/nlohmann_json` is then a complete copy of this source tree.
### FetchContent
Since CMake v3.11, [FetchContent](https://cmake.org/cmake/help/v3.11/module/FetchContent.html) can be used to
automatically download a release as a dependency at configure time.
!!! example
```cmake title="CMakeLists.txt"
cmake_minimum_required(VERSION 3.11)
project(ExampleProject LANGUAGES CXX)
include(FetchContent)
FetchContent_Declare(json URL https://github.com/nlohmann/json/releases/download/v3.12.0/json.tar.xz)
FetchContent_MakeAvailable(json)
add_executable(example example.cpp)
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
!!! Note
It is recommended to use the URL approach described above which is supported as of version 3.10.0. It is also
possible to pass the Git repository like
```cmake
FetchContent_Declare(json
GIT_REPOSITORY https://github.com/nlohmann/json
GIT_TAG v3.12.0
)
```
However, the repository <https://github.com/nlohmann/json> download size is quite large.
## CMake Options
### `JSON_BuildTests`
Build the unit tests when [`BUILD_TESTING`](https://cmake.org/cmake/help/latest/command/enable_testing.html) is enabled. This option is `ON` by default if the library's CMake project is the top project. That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.
### `JSON_CI`
Enable CI build targets. The exact targets are used during the several CI steps and are subject to change without notice. This option is `OFF` by default.
### `JSON_Diagnostics`
Enable [extended diagnostic messages](../home/exceptions.md#extended-diagnostic-messages) by defining macro [`JSON_DIAGNOSTICS`](../api/macros/json_diagnostics.md). This option is `OFF` by default.
### `JSON_Diagnostic_Positions`
Enable position diagnostics by defining macro [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md). This option is `OFF` by default.
### `JSON_DisableEnumSerialization`
Disable default `enum` serialization by defining the macro
[`JSON_DISABLE_ENUM_SERIALIZATION`](../api/macros/json_disable_enum_serialization.md). This option is `OFF` by default.
### `JSON_FastTests`
Skip expensive/slow test suites. This option is `OFF` by default. Depends on `JSON_BuildTests`.
### `JSON_GlobalUDLs`
Place user-defined string literals in the global namespace by defining the macro
[`JSON_USE_GLOBAL_UDLS`](../api/macros/json_use_global_udls.md). This option is `OFF` by default.
### `JSON_ImplicitConversions`
Enable implicit conversions by defining macro [`JSON_USE_IMPLICIT_CONVERSIONS`](../api/macros/json_use_implicit_conversions.md). This option is `ON` by default.
### `JSON_Install`
Install CMake targets during install step. This option is `ON` by default if the library's CMake project is the top project.
### `JSON_LegacyDiscardedValueComparison`
Enable the (incorrect) legacy comparison behavior of discarded JSON values by defining macro [`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../api/macros/json_use_legacy_discarded_value_comparison.md). This option is `OFF` by default.
### `JSON_MultipleHeaders`
Use the non-amalgamated version of the library. This option is `ON` by default.
### `JSON_SystemInclude`
Treat the library headers like system headers (i.e., adding `SYSTEM` to the [`target_include_directories`](https://cmake.org/cmake/help/latest/command/target_include_directories.html) call) to check for this library by tools like Clang-Tidy. This option is `OFF` by default.
### `JSON_Valgrind`
Execute the test suite with [Valgrind](https://valgrind.org). This option is `OFF` by default. Depends on `JSON_BuildTests`.
### `NLOHMANN_JSON_BUILD_MODULES`
Build the experimental [C++ module](../features/modules.md) `nlohmann.json` (requires CMake 3.28 or later and C++20).
This option is `OFF` by default.
integration/cmake/index.html
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<span class=w> </span><span class=s>GIT_REPOSITORY</span><span class=w> </span><span class=s>https://github.com/nlohmann/json</span>
<span class=w> </span><span class=s>GIT_TAG</span><span class=w> </span><span class=s>v3.12.0</span>
<span class=p>)</span>
</code></pre></div> <p>However, the repository <a href="https://github.com/nlohmann/json">https://github.com/nlohmann/json</a> download size is quite large.</p> </div> <h2 id=cmake-options>CMake Options<a class=headerlink href=#cmake-options title="Permanent link">&para;</a></h2> <h3 id=json_buildtests><code>JSON_BuildTests</code><a class=headerlink href=#json_buildtests title="Permanent link">&para;</a></h3> <p>Build the unit tests when <a href="https://cmake.org/cmake/help/latest/command/enable_testing.html"><code>BUILD_TESTING</code></a> is enabled. This option is <code>ON</code> by default if the library's CMake project is the top project. That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.</p> <h3 id=json_ci><code>JSON_CI</code><a class=headerlink href=#json_ci title="Permanent link">&para;</a></h3> <p>Enable <abbr title="Continuous Integration">CI</abbr> build targets. The exact targets are used during the several <abbr title="Continuous Integration">CI</abbr> steps and are subject to change without notice. This option is <code>OFF</code> by default.</p> <h3 id=json_diagnostics><code>JSON_Diagnostics</code><a class=headerlink href=#json_diagnostics title="Permanent link">&para;</a></h3> <p>Enable <a href=../../home/exceptions/#extended-diagnostic-messages>extended diagnostic messages</a> by defining macro <a href=../../api/macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_diagnostic_positions><code>JSON_Diagnostic_Positions</code><a class=headerlink href=#json_diagnostic_positions title="Permanent link">&para;</a></h3> <p>Enable position diagnostics by defining macro <a href=../../api/macros/json_diagnostic_positions/ ><code>JSON_DIAGNOSTIC_POSITIONS</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_disableenumserialization><code>JSON_DisableEnumSerialization</code><a class=headerlink href=#json_disableenumserialization title="Permanent link">&para;</a></h3> <p>Disable default <code>enum</code> serialization by defining the macro <a href=../../api/macros/json_disable_enum_serialization/ ><code>JSON_DISABLE_ENUM_SERIALIZATION</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_fasttests><code>JSON_FastTests</code><a class=headerlink href=#json_fasttests title="Permanent link">&para;</a></h3> <p>Skip expensive/slow test suites. This option is <code>OFF</code> by default. Depends on <code>JSON_BuildTests</code>.</p> <h3 id=json_globaludls><code>JSON_GlobalUDLs</code><a class=headerlink href=#json_globaludls title="Permanent link">&para;</a></h3> <p>Place user-defined string literals in the global namespace by defining the macro <a href=../../api/macros/json_use_global_udls/ ><code>JSON_USE_GLOBAL_UDLS</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_implicitconversions><code>JSON_ImplicitConversions</code><a class=headerlink href=#json_implicitconversions title="Permanent link">&para;</a></h3> <p>Enable implicit conversions by defining macro <a href=../../api/macros/json_use_implicit_conversions/ ><code>JSON_USE_IMPLICIT_CONVERSIONS</code></a>. This option is <code>ON</code> by default.</p> <h3 id=json_install><code>JSON_Install</code><a class=headerlink href=#json_install title="Permanent link">&para;</a></h3> <p>Install CMake targets during install step. This option is <code>ON</code> by default if the library's CMake project is the top project.</p> <h3 id=json_legacydiscardedvaluecomparison><code>JSON_LegacyDiscardedValueComparison</code><a class=headerlink href=#json_legacydiscardedvaluecomparison title="Permanent link">&para;</a></h3> <p>Enable the (incorrect) legacy comparison behavior of discarded <abbr title="JavaScript Object Notation">JSON</abbr> values by defining macro <a href=../../api/macros/json_use_legacy_discarded_value_comparison/ ><code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_multipleheaders><code>JSON_MultipleHeaders</code><a class=headerlink href=#json_multipleheaders title="Permanent link">&para;</a></h3> <p>Use the non-amalgamated version of the library. This option is <code>ON</code> by default.</p> <h3 id=json_systeminclude><code>JSON_SystemInclude</code><a class=headerlink href=#json_systeminclude title="Permanent link">&para;</a></h3> <p>Treat the library headers like system headers (i.e., adding <code>SYSTEM</code> to the <a href="https://cmake.org/cmake/help/latest/command/target_include_directories.html"><code>target_include_directories</code></a> call) to check for this library by tools like Clang-Tidy. This option is <code>OFF</code> by default.</p> <h3 id=json_valgrind><code>JSON_Valgrind</code><a class=headerlink href=#json_valgrind title="Permanent link">&para;</a></h3> <p>Execute the test suite with <a href="https://valgrind.org">Valgrind</a>. This option is <code>OFF</code> by deLine truncated
</code></pre></div> <p>However, the repository <a href="https://github.com/nlohmann/json">https://github.com/nlohmann/json</a> download size is quite large.</p> </div> <h2 id=cmake-options>CMake Options<a class=headerlink href=#cmake-options title="Permanent link">&para;</a></h2> <h3 id=json_buildtests><code>JSON_BuildTests</code><a class=headerlink href=#json_buildtests title="Permanent link">&para;</a></h3> <p>Build the unit tests when <a href="https://cmake.org/cmake/help/latest/command/enable_testing.html"><code>BUILD_TESTING</code></a> is enabled. This option is <code>ON</code> by default if the library's CMake project is the top project. That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.</p> <h3 id=json_ci><code>JSON_CI</code><a class=headerlink href=#json_ci title="Permanent link">&para;</a></h3> <p>Enable <abbr title="Continuous Integration">CI</abbr> build targets. The exact targets are used during the several <abbr title="Continuous Integration">CI</abbr> steps and are subject to change without notice. This option is <code>OFF</code> by default.</p> <h3 id=json_diagnostics><code>JSON_Diagnostics</code><a class=headerlink href=#json_diagnostics title="Permanent link">&para;</a></h3> <p>Enable <a href=../../home/exceptions/#extended-diagnostic-messages>extended diagnostic messages</a> by defining macro <a href=../../api/macros/json_diagnostics/ ><code>JSON_DIAGNOSTICS</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_diagnostic_positions><code>JSON_Diagnostic_Positions</code><a class=headerlink href=#json_diagnostic_positions title="Permanent link">&para;</a></h3> <p>Enable position diagnostics by defining macro <a href=../../api/macros/json_diagnostic_positions/ ><code>JSON_DIAGNOSTIC_POSITIONS</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_disableenumserialization><code>JSON_DisableEnumSerialization</code><a class=headerlink href=#json_disableenumserialization title="Permanent link">&para;</a></h3> <p>Disable default <code>enum</code> serialization by defining the macro <a href=../../api/macros/json_disable_enum_serialization/ ><code>JSON_DISABLE_ENUM_SERIALIZATION</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_fasttests><code>JSON_FastTests</code><a class=headerlink href=#json_fasttests title="Permanent link">&para;</a></h3> <p>Skip expensive/slow test suites. This option is <code>OFF</code> by default. Depends on <code>JSON_BuildTests</code>.</p> <h3 id=json_globaludls><code>JSON_GlobalUDLs</code><a class=headerlink href=#json_globaludls title="Permanent link">&para;</a></h3> <p>Place user-defined string literals in the global namespace by defining the macro <a href=../../api/macros/json_use_global_udls/ ><code>JSON_USE_GLOBAL_UDLS</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_implicitconversions><code>JSON_ImplicitConversions</code><a class=headerlink href=#json_implicitconversions title="Permanent link">&para;</a></h3> <p>Enable implicit conversions by defining macro <a href=../../api/macros/json_use_implicit_conversions/ ><code>JSON_USE_IMPLICIT_CONVERSIONS</code></a>. This option is <code>ON</code> by default.</p> <h3 id=json_install><code>JSON_Install</code><a class=headerlink href=#json_install title="Permanent link">&para;</a></h3> <p>Install CMake targets during install step. This option is <code>ON</code> by default if the library's CMake project is the top project.</p> <h3 id=json_legacydiscardedvaluecomparison><code>JSON_LegacyDiscardedValueComparison</code><a class=headerlink href=#json_legacydiscardedvaluecomparison title="Permanent link">&para;</a></h3> <p>Enable the (incorrect) legacy comparison behavior of discarded <abbr title="JavaScript Object Notation">JSON</abbr> values by defining macro <a href=../../api/macros/json_use_legacy_discarded_value_comparison/ ><code>JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON</code></a>. This option is <code>OFF</code> by default.</p> <h3 id=json_multipleheaders><code>JSON_MultipleHeaders</code><a class=headerlink href=#json_multipleheaders title="Permanent link">&para;</a></h3> <p>Use the non-amalgamated version of the library. This option is <code>ON</code> by default.</p> <h3 id=json_systeminclude><code>JSON_SystemInclude</code><a class=headerlink href=#json_systeminclude title="Permanent link">&para;</a></h3> <p>Treat the library headers like system headers (i.e., adding <code>SYSTEM</code> to the <a href="https://cmake.org/cmake/help/latest/command/target_include_directories.html"><code>target_include_directories</code></a> call) to check for this library by tools like Clang-Tidy. This option is <code>OFF</code> by default.</p> <h3 id=json_valgrind><code>JSON_Valgrind</code><a class=headerlink href=#json_valgrind title="Permanent link">&para;</a></h3> <p>Execute the test suite with <a href="https://valgrind.org">Valgrind</a>. This option is <code>OFF</code> by deLine truncated
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# CMake
## Integration
You can use the `nlohmann_json::nlohmann_json` interface target in CMake. This target populates the appropriate usage requirements for [`INTERFACE_INCLUDE_DIRECTORIES`](https://cmake.org/cmake/help/latest/prop_tgt/INTERFACE_INCLUDE_DIRECTORIES.html) to point to the appropriate include directories and [`INTERFACE_COMPILE_FEATURES`](https://cmake.org/cmake/help/latest/prop_tgt/INTERFACE_COMPILE_FEATURES.html) for the necessary C++11 flags.
### External
To use this library from a CMake project, you can locate it directly with [`find_package()`](https://cmake.org/cmake/help/latest/command/find_package.html) and use the namespaced imported target from the generated package configuration:
Example
CMakeLists.txt
```
cmake_minimum_required(VERSION 3.5)
project(ExampleProject LANGUAGES CXX)
find_package(nlohmann_json 3.12.0 REQUIRED)
add_executable(example example.cpp)
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
The package configuration file, `nlohmann_jsonConfig.cmake`, can be used either from an install tree or directly out of the build tree.
### Embedded
To embed the library directly into an existing CMake project, place the entire source tree in a subdirectory and call `add_subdirectory()` in your `CMakeLists.txt` file.
Example
CMakeLists.txt
```
cmake_minimum_required(VERSION 3.5)
project(ExampleProject LANGUAGES CXX)
# If you only include this third party in PRIVATE source files, you do not need to install it
# when your main project gets installed.
set(JSON_Install OFF CACHE INTERNAL "")
add_subdirectory(nlohmann_json)
add_executable(example example.cpp)
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
Note
Do not use `include(nlohmann_json/CMakeLists.txt)`, since that carries with it unintended consequences that will break the build. It is generally discouraged (although not necessarily well documented as such) to use `include(...)` for pulling in other CMake projects anyways.
### Supporting Both
To allow your project to support either an externally supplied or an embedded JSON library, you can use a pattern akin to the following.
Example
CMakeLists.txt
```
project(ExampleProject LANGUAGES CXX)
option(EXAMPLE_USE_EXTERNAL_JSON "Use an external JSON library" OFF)
add_subdirectory(thirdparty)
add_executable(example example.cpp)
# Note that the namespaced target will always be available regardless of the import method
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
thirdparty/CMakeLists.txt
```
if(EXAMPLE_USE_EXTERNAL_JSON)
find_package(nlohmann_json 3.12.0 REQUIRED)
else()
set(JSON_BuildTests OFF CACHE INTERNAL "")
add_subdirectory(nlohmann_json)
endif()
```
`thirdparty/nlohmann_json` is then a complete copy of this source tree.
### FetchContent
Since CMake v3.11, [FetchContent](https://cmake.org/cmake/help/v3.11/module/FetchContent.html) can be used to automatically download a release as a dependency at configure time.
Example
CMakeLists.txt
```
cmake_minimum_required(VERSION 3.11)
project(ExampleProject LANGUAGES CXX)
include(FetchContent)
FetchContent_Declare(json URL https://github.com/nlohmann/json/releases/download/v3.12.0/json.tar.xz)
FetchContent_MakeAvailable(json)
add_executable(example example.cpp)
target_link_libraries(example PRIVATE nlohmann_json::nlohmann_json)
```
Note
It is recommended to use the URL approach described above which is supported as of version 3.10.0. It is also possible to pass the Git repository like
```
FetchContent_Declare(json
GIT_REPOSITORY https://github.com/nlohmann/json
GIT_TAG v3.12.0
)
```
However, the repository <https://github.com/nlohmann/json> download size is quite large.
## CMake Options
### `JSON_BuildTests`
Build the unit tests when [`BUILD_TESTING`](https://cmake.org/cmake/help/latest/command/enable_testing.html) is enabled. This option is `ON` by default if the library's CMake project is the top project. That is, when integrating the library as described above, the test suite is not built unless explicitly switched on with this option.
### `JSON_CI`
Enable CI build targets. The exact targets are used during the several CI steps and are subject to change without notice. This option is `OFF` by default.
### `JSON_Diagnostics`
Enable [extended diagnostic messages](https://json.nlohmann.me/home/exceptions/#extended-diagnostic-messages) by defining macro [`JSON_DIAGNOSTICS`](https://json.nlohmann.me/api/macros/json_diagnostics/index.md). This option is `OFF` by default.
### `JSON_Diagnostic_Positions`
Enable position diagnostics by defining macro [`JSON_DIAGNOSTIC_POSITIONS`](https://json.nlohmann.me/api/macros/json_diagnostic_positions/index.md). This option is `OFF` by default.
### `JSON_DisableEnumSerialization`
Disable default `enum` serialization by defining the macro [`JSON_DISABLE_ENUM_SERIALIZATION`](https://json.nlohmann.me/api/macros/json_disable_enum_serialization/index.md). This option is `OFF` by default.
### `JSON_FastTests`
Skip expensive/slow test suites. This option is `OFF` by default. Depends on `JSON_BuildTests`.
### `JSON_GlobalUDLs`
Place user-defined string literals in the global namespace by defining the macro [`JSON_USE_GLOBAL_UDLS`](https://json.nlohmann.me/api/macros/json_use_global_udls/index.md). This option is `OFF` by default.
### `JSON_ImplicitConversions`
Enable implicit conversions by defining macro [`JSON_USE_IMPLICIT_CONVERSIONS`](https://json.nlohmann.me/api/macros/json_use_implicit_conversions/index.md). This option is `ON` by default.
### `JSON_Install`
Install CMake targets during install step. This option is `ON` by default if the library's CMake project is the top project.
### `JSON_LegacyDiscardedValueComparison`
Enable the (incorrect) legacy comparison behavior of discarded JSON values by defining macro [`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](https://json.nlohmann.me/api/macros/json_use_legacy_discarded_value_comparison/index.md). This option is `OFF` by default.
### `JSON_MultipleHeaders`
Use the non-amalgamated version of the library. This option is `ON` by default.
### `JSON_SystemInclude`
Treat the library headers like system headers (i.e., adding `SYSTEM` to the [`target_include_directories`](https://cmake.org/cmake/help/latest/command/target_include_directories.html) call) to check for this library by tools like Clang-Tidy. This option is `OFF` by default.
### `JSON_Valgrind`
Execute the test suite with [Valgrind](https://valgrind.org). This option is `OFF` by default. Depends on `JSON_BuildTests`.
### `NLOHMANN_JSON_BUILD_MODULES`
Build the experimental [C++ module](https://json.nlohmann.me/features/modules/index.md) `nlohmann.json` (requires CMake 3.28 or later and C++20). This option is `OFF` by default.
integration/index.html
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<span class=c1>// for convenience</span>
<span class=k>using</span><span class=w> </span><span class=n>json</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>nlohmann</span><span class=o>::</span><span class=n>json</span><span class=p>;</span>
</code></pre></div> <p>to the files you want to process <abbr title="JavaScript Object Notation">JSON</abbr> and set the necessary switches to enable C++11 (e.g., <code>-std=c++11</code> for <abbr title="GNU Compiler Collection">GCC</abbr> and Clang).</p> <p>You can further use file <a href="https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp"><code>single_include/nlohmann/json_fwd.hpp</code></a> for forward declarations.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 4, 2026 09:13:25 UTC">July 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <p>to the files you want to process <abbr title="JavaScript Object Notation">JSON</abbr> and set the necessary switches to enable C++11 (e.g., <code>-std=c++11</code> for <abbr title="GNU Compiler Collection">GCC</abbr> and Clang).</p> <p>You can further use file <a href="https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp"><code>single_include/nlohmann/json_fwd.hpp</code></a> for forward declarations.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 8, 2026 18:18:24 UTC">July 8, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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integration/index.md
+14
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# Header only
[`json.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json.hpp) is the single required file in `single_include/nlohmann` or [released here](https://github.com/nlohmann/json/releases). You need to add
```
#include <nlohmann/json.hpp>
// for convenience
using json = nlohmann::json;
```
to the files you want to process JSON and set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).
You can further use file [`single_include/nlohmann/json_fwd.hpp`](https://github.com/nlohmann/json/blob/develop/single_include/nlohmann/json_fwd.hpp) for forward declarations.
integration/migration_guide.md
+260
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# Migration Guide
This page collects some guidelines on how to future-proof your code for future versions of this library.
## Replace deprecated functions
The following functions have been deprecated and will be removed in the next major version (i.e., 4.0.0). All
deprecations are annotated with
[`HEDLEY_DEPRECATED_FOR`](https://nemequ.github.io/hedley/api-reference.html#HEDLEY_DEPRECATED_FOR) to report which
function to use instead.
#### Parsing
- Function `friend std::istream& operator<<(basic_json&, std::istream&)` is deprecated since 3.0.0. Please use
[`friend std::istream& operator>>(std::istream&, basic_json&)`](../api/operator_gtgt.md) instead.
=== "Deprecated"
```cpp
nlohmann::json j;
std::stringstream ss("[1,2,3]");
j << ss;
```
=== "Future-proof"
```cpp
nlohmann::json j;
std::stringstream ss("[1,2,3]");
ss >> j;
```
- Passing iterator pairs or pointer/length pairs to parsing functions ([`parse`](../api/basic_json/parse.md),
[`accept`](../api/basic_json/accept.md), [`sax_parse`](../api/basic_json/sax_parse.md),
[`from_cbor`](../api/basic_json/from_cbor.md), [`from_msgpack`](../api/basic_json/from_msgpack.md),
[`from_ubjson`](../api/basic_json/from_ubjson.md), and [`from_bson`](../api/basic_json/from_bson.md) via initializer
lists is deprecated since 3.8.0. Instead, pass two iterators; for instance, call `from_cbor(ptr, ptr+len)` instead of
`from_cbor({ptr, len})`.
=== "Deprecated"
```cpp
const char* s = "[1,2,3]";
bool ok = nlohmann::json::accept({s, s + std::strlen(s)});
```
=== "Future-proof"
```cpp
const char* s = "[1,2,3]";
bool ok = nlohmann::json::accept(s, s + std::strlen(s));
```
#### JSON Pointers
- Comparing JSON Pointers with strings via [`operator==`](../api/json_pointer/operator_eq.md) and
[`operator!=`](../api/json_pointer/operator_ne.md) is deprecated since 3.11.2. To compare a
[`json_pointer`](../api/json_pointer/index.md) `p` with a string `s`, convert `s` to a `json_pointer` first and use
[`json_pointer::operator==`](../api/json_pointer/operator_eq.md) or
[`json_pointer::operator!=`](../api/json_pointer/operator_ne.md).
=== "Deprecated"
```cpp
nlohmann::json::json_pointer lhs("/foo/bar/1");
assert(lhs == "/foo/bar/1");
```
=== "Future-proof"
```cpp
nlohmann::json::json_pointer lhs("/foo/bar/1");
assert(lhs == nlohmann::json::json_pointer("/foo/bar/1"));
```
- The implicit conversion from JSON Pointers to string
([`json_pointer::operator string_t`](../api/json_pointer/operator_string_t.md)) is deprecated since 3.11.0. Use
[`json_pointer::to_string`](../api/json_pointer/to_string.md) instead.
=== "Deprecated"
```cpp
nlohmann::json::json_pointer ptr("/foo/bar/1");
std::string s = ptr;
```
=== "Future-proof"
```cpp
nlohmann::json::json_pointer ptr("/foo/bar/1");
std::string s = ptr.to_string();
```
- Passing a `basic_json` specialization as template parameter `RefStringType` to
[`json_pointer`](../api/json_pointer/index.md) is deprecated since 3.11.0. The string type can now be directly
provided.
=== "Deprecated"
```cpp
using my_json = nlohmann::basic_json<std::map, std::vector, my_string_type>;
nlohmann::json_pointer<my_json> ptr("/foo/bar/1");
```
=== "Future-proof"
```cpp
nlohmann::json_pointer<my_string_type> ptr("/foo/bar/1");
```
Thereby, `nlohmann::my_json::json_pointer` is an alias for `nlohmann::json_pointer<my_string_type>` and is always an
alias to the `json_pointer` with the appropriate string type for all specializations of `basic_json`.
#### Miscellaneous functions
- The function `iterator_wrapper` is deprecated since 3.1.0. Please use the member function
[`items`](../api/basic_json/items.md) instead.
=== "Deprecated"
```cpp
for (auto &x : nlohmann::json::iterator_wrapper(j))
{
std::cout << x.key() << ":" << x.value() << std::endl;
}
```
=== "Future-proof"
```cpp
for (auto &x : j.items())
{
std::cout << x.key() << ":" << x.value() << std::endl;
}
```
- Function `friend std::ostream& operator>>(const basic_json&, std::ostream&)` is deprecated since 3.0.0. Please use
[`friend operator<<(std::ostream&, const basic_json&)`](../api/operator_ltlt.md) instead.
=== "Deprecated"
```cpp
j >> std::cout;
```
=== "Future-proof"
```cpp
std::cout << j;
```
- The legacy comparison behavior for discarded values is deprecated since 3.11.0. It is already disabled by default and
can still be enabled by defining
[`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](../api/macros/json_use_legacy_discarded_value_comparison.md) to `1`.
=== "Deprecated"
```cpp
#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 1
#include <nlohmann/json.hpp>
```
=== "Future-proof"
```cpp
#include <nlohmann/json.hpp>
```
## Replace implicit conversions
Implicit conversions via [`operator ValueType`](../api/basic_json/operator_ValueType.md) will be switched off by default
in the next major release of the library.
You can prepare existing code by already defining
[`JSON_USE_IMPLICIT_CONVERSIONS`](../api/macros/json_use_implicit_conversions.md) to `0` and replace any implicit
conversions with calls to [`get`](../api/basic_json/get.md), [`get_to`](../api/basic_json/get_to.md),
[`get_ref`](../api/basic_json/get_ref.md), or [`get_ptr`](../api/basic_json/get_ptr.md).
=== "Deprecated"
```cpp
nlohmann::json j = "Hello, world!";
std::string s = j;
```
=== "Future-proof"
```cpp
nlohmann::json j = "Hello, world!";
auto s = j.get<std::string>();
```
=== "Future-proof (alternative)"
```cpp
nlohmann::json j = "Hello, world!";
std::string s;
j.get_to(s);
```
## Import namespace `literals` for UDLs
The user-defined string literals [`operator""_json`](../api/operator_literal_json.md) and
[`operator""_json_pointer`](../api/operator_literal_json_pointer.md) will be removed from the global namespace in the
next major release of the library.
=== "Deprecated"
```cpp
nlohmann::json j = "[1,2,3]"_json;
```
=== "Future-proof"
```cpp
using namespace nlohmann::literals;
nlohmann::json j = "[1,2,3]"_json;
```
To prepare existing code, define [`JSON_USE_GLOBAL_UDLS`](../api/macros/json_use_global_udls.md) to `0` and bring the
string literals into scope where needed.
## Do not hard-code the complete library namespace
The [`nlohmann` namespace](../features/namespace.md) contains a sub-namespace to avoid problems when different
versions or configurations of the library are used in the same project. Always use `nlohmann` as namespace or, when the
exact version and configuration is relevant, use macro
[`NLOHMANN_JSON_NAMESPACE`](../api/macros/nlohmann_json_namespace.md) to denote the namespace.
=== "Dangerous"
```cpp
void to_json(nlohmann::json_abi_v3_11_2::json& j, const person& p)
{
j["age"] = p.age;
}
```
=== "Future-proof"
```cpp
void to_json(nlohmann::json& j, const person& p)
{
j["age"] = p.age;
}
```
=== "Future-proof (alternative)"
```cpp
void to_json(NLOHMANN_JSON_NAMESPACE::json& j, const person& p)
{
j["age"] = p.age;
}
```
## Do not use the `details` namespace
The `details` namespace is not part of the public API of the library and can change in any version without an
announcement. Do not rely on any function or type in the `details` namespace.
integration/migration_guide/index.html
+1 -1
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@@ -54,4 +54,4 @@
<span class=p>{</span>
<span class=w> </span><span class=n>j</span><span class=p>[</span><span class=s>&quot;age&quot;</span><span class=p>]</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=n>p</span><span class=p>.</span><span class=n>age</span><span class=p>;</span>
<span class=p>}</span>
</code></pre></div> </div> </div> </div> <h2 id=do-not-use-the-details-namespace>Do not use the <code>details</code> namespace<a class=headerlink href=#do-not-use-the-details-namespace title="Permanent link">&para;</a></h2> <p>The <code>details</code> namespace is not part of the public <abbr title="Application Programming Interfaces">API</abbr> of the library and can change in any version without an announcement. Do not rely on any function or type in the <code>details</code> namespace.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 4, 2026 09:13:25 UTC">July 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 384 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fonLine truncated
</code></pre></div> </div> </div> </div> <h2 id=do-not-use-the-details-namespace>Do not use the <code>details</code> namespace<a class=headerlink href=#do-not-use-the-details-namespace title="Permanent link">&para;</a></h2> <p>The <code>details</code> namespace is not part of the public <abbr title="Application Programming Interfaces">API</abbr> of the library and can change in any version without an announcement. Do not rely on any function or type in the <code>details</code> namespace.</p> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 8, 2026 18:18:24 UTC">July 8, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C436.2 457.8 504 362.9 504 252 504 113.3 391.5 8 252.8 8M105.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1m-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7m32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1m-11.4-14.7c-1.6 1-1.6 3.6 0 5.9s4.3 3.3 5.6 2.3c1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2"/></svg> </a> <a href="https://www.linkedin.com/in/nielslohmann/" target="_blank" rel="noopener" title="www.linkedin.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 448 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M416 32H31.9C14.3 32 0 46.5 0 64.3v383.4C0 465.5 14.3 480 31.9 480H416c17.6 0 32-14.5 32-32.3V64.3c0-17.8-14.4-32.3-32-32.3M135.4 416H69V202.2h66.5V416zM102.2 96a38.5 38.5 0 1 1 0 77 38.5 38.5 0 1 1 0-77m282.1 320h-66.4V312c0-24.8-.5-56.7-34.5-56.7-34.6 0-39.9 27-39.9 54.9V416h-66.4V202.2h63.7v29.2h.9c8.9-16.8 30.6-34.5 62.9-34.5 67.2 0 79.7 44.3 79.7 101.9z"/></svg> </a> <a href="https://www.xing.com/profile/Niels_Lohmann" target="_blank" rel="noopener" title="www.xing.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 384 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fonLine truncated
integration/migration_guide/index.md
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# Migration Guide
This page collects some guidelines on how to future-proof your code for future versions of this library.
## Replace deprecated functions
The following functions have been deprecated and will be removed in the next major version (i.e., 4.0.0). All deprecations are annotated with [`HEDLEY_DEPRECATED_FOR`](https://nemequ.github.io/hedley/api-reference.html#HEDLEY_DEPRECATED_FOR) to report which function to use instead.
#### Parsing
- Function `friend std::istream& operator<<(basic_json&, std::istream&)` is deprecated since 3.0.0. Please use [`friend std::istream& operator>>(std::istream&, basic_json&)`](https://json.nlohmann.me/api/operator_gtgt/index.md) instead.
```
nlohmann::json j;
std::stringstream ss("[1,2,3]");
j << ss;
```
```
nlohmann::json j;
std::stringstream ss("[1,2,3]");
ss >> j;
```
- Passing iterator pairs or pointer/length pairs to parsing functions ([`parse`](https://json.nlohmann.me/api/basic_json/parse/index.md), [`accept`](https://json.nlohmann.me/api/basic_json/accept/index.md), [`sax_parse`](https://json.nlohmann.me/api/basic_json/sax_parse/index.md), [`from_cbor`](https://json.nlohmann.me/api/basic_json/from_cbor/index.md), [`from_msgpack`](https://json.nlohmann.me/api/basic_json/from_msgpack/index.md), [`from_ubjson`](https://json.nlohmann.me/api/basic_json/from_ubjson/index.md), and [`from_bson`](https://json.nlohmann.me/api/basic_json/from_bson/index.md) via initializer lists is deprecated since 3.8.0. Instead, pass two iterators; for instance, call `from_cbor(ptr, ptr+len)` instead of `from_cbor({ptr, len})`.
```
const char* s = "[1,2,3]";
bool ok = nlohmann::json::accept({s, s + std::strlen(s)});
```
```
const char* s = "[1,2,3]";
bool ok = nlohmann::json::accept(s, s + std::strlen(s));
```
#### JSON Pointers
- Comparing JSON Pointers with strings via [`operator==`](https://json.nlohmann.me/api/json_pointer/operator_eq/index.md) and [`operator!=`](https://json.nlohmann.me/api/json_pointer/operator_ne/index.md) is deprecated since 3.11.2. To compare a [`json_pointer`](https://json.nlohmann.me/api/json_pointer/index.md) `p` with a string `s`, convert `s` to a `json_pointer` first and use [`json_pointer::operator==`](https://json.nlohmann.me/api/json_pointer/operator_eq/index.md) or [`json_pointer::operator!=`](https://json.nlohmann.me/api/json_pointer/operator_ne/index.md).
```
nlohmann::json::json_pointer lhs("/foo/bar/1");
assert(lhs == "/foo/bar/1");
```
```
nlohmann::json::json_pointer lhs("/foo/bar/1");
assert(lhs == nlohmann::json::json_pointer("/foo/bar/1"));
```
- The implicit conversion from JSON Pointers to string ([`json_pointer::operator string_t`](https://json.nlohmann.me/api/json_pointer/operator_string_t/index.md)) is deprecated since 3.11.0. Use [`json_pointer::to_string`](https://json.nlohmann.me/api/json_pointer/to_string/index.md) instead.
```
nlohmann::json::json_pointer ptr("/foo/bar/1");
std::string s = ptr;
```
```
nlohmann::json::json_pointer ptr("/foo/bar/1");
std::string s = ptr.to_string();
```
- Passing a `basic_json` specialization as template parameter `RefStringType` to [`json_pointer`](https://json.nlohmann.me/api/json_pointer/index.md) is deprecated since 3.11.0. The string type can now be directly provided.
```
using my_json = nlohmann::basic_json<std::map, std::vector, my_string_type>;
nlohmann::json_pointer<my_json> ptr("/foo/bar/1");
```
```
nlohmann::json_pointer<my_string_type> ptr("/foo/bar/1");
```
Thereby, `nlohmann::my_json::json_pointer` is an alias for `nlohmann::json_pointer<my_string_type>` and is always an alias to the `json_pointer` with the appropriate string type for all specializations of `basic_json`.
#### Miscellaneous functions
- The function `iterator_wrapper` is deprecated since 3.1.0. Please use the member function [`items`](https://json.nlohmann.me/api/basic_json/items/index.md) instead.
```
for (auto &x : nlohmann::json::iterator_wrapper(j))
{
std::cout << x.key() << ":" << x.value() << std::endl;
}
```
```
for (auto &x : j.items())
{
std::cout << x.key() << ":" << x.value() << std::endl;
}
```
- Function `friend std::ostream& operator>>(const basic_json&, std::ostream&)` is deprecated since 3.0.0. Please use [`friend operator<<(std::ostream&, const basic_json&)`](https://json.nlohmann.me/api/operator_ltlt/index.md) instead.
```
j >> std::cout;
```
```
std::cout << j;
```
- The legacy comparison behavior for discarded values is deprecated since 3.11.0. It is already disabled by default and can still be enabled by defining [`JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON`](https://json.nlohmann.me/api/macros/json_use_legacy_discarded_value_comparison/index.md) to `1`.
```
#define JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON 1
#include <nlohmann/json.hpp>
```
```
#include <nlohmann/json.hpp>
```
## Replace implicit conversions
Implicit conversions via [`operator ValueType`](https://json.nlohmann.me/api/basic_json/operator_ValueType/index.md) will be switched off by default in the next major release of the library.
You can prepare existing code by already defining [`JSON_USE_IMPLICIT_CONVERSIONS`](https://json.nlohmann.me/api/macros/json_use_implicit_conversions/index.md) to `0` and replace any implicit conversions with calls to [`get`](https://json.nlohmann.me/api/basic_json/get/index.md), [`get_to`](https://json.nlohmann.me/api/basic_json/get_to/index.md), [`get_ref`](https://json.nlohmann.me/api/basic_json/get_ref/index.md), or [`get_ptr`](https://json.nlohmann.me/api/basic_json/get_ptr/index.md).
```
nlohmann::json j = "Hello, world!";
std::string s = j;
```
```
nlohmann::json j = "Hello, world!";
auto s = j.get<std::string>();
```
```
nlohmann::json j = "Hello, world!";
std::string s;
j.get_to(s);
```
## Import namespace `literals` for UDLs
The user-defined string literals [`operator""_json`](https://json.nlohmann.me/api/operator_literal_json/index.md) and [`operator""_json_pointer`](https://json.nlohmann.me/api/operator_literal_json_pointer/index.md) will be removed from the global namespace in the next major release of the library.
```
nlohmann::json j = "[1,2,3]"_json;
```
```
using namespace nlohmann::literals;
nlohmann::json j = "[1,2,3]"_json;
```
To prepare existing code, define [`JSON_USE_GLOBAL_UDLS`](https://json.nlohmann.me/api/macros/json_use_global_udls/index.md) to `0` and bring the string literals into scope where needed.
## Do not hard-code the complete library namespace
The [`nlohmann` namespace](https://json.nlohmann.me/features/namespace/index.md) contains a sub-namespace to avoid problems when different versions or configurations of the library are used in the same project. Always use `nlohmann` as namespace or, when the exact version and configuration is relevant, use macro [`NLOHMANN_JSON_NAMESPACE`](https://json.nlohmann.me/api/macros/nlohmann_json_namespace/index.md) to denote the namespace.
```
void to_json(nlohmann::json_abi_v3_11_2::json& j, const person& p)
{
j["age"] = p.age;
}
```
```
void to_json(nlohmann::json& j, const person& p)
{
j["age"] = p.age;
}
```
```
void to_json(NLOHMANN_JSON_NAMESPACE::json& j, const person& p)
{
j["age"] = p.age;
}
```
## Do not use the `details` namespace
The `details` namespace is not part of the public API of the library and can change in any version without an announcement. Do not rely on any function or type in the `details` namespace.
integration/package_managers.md
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# Package Managers
<p markdown style="text-align: center">
![Homebrew](../images/package_managers/homebrew.svg){: style="height:1em"}&nbsp;[**Homebrew**](#homebrew) `nlohmann-json` &emsp;
![Meson](../images/package_managers/meson.svg){: style="height:1em"}&nbsp;[**Meson**](#meson) `nlohmann_json` &emsp;
![Bazel](../images/package_managers/bazel.svg){: style="height:1em"}&nbsp;[**Bazel**](#bazel) `nlohmann_json`<br>
![Conan](../images/package_managers/conan.svg){: style="height:1em"}&nbsp;[**Conan**](#conan) `nlohmann_json` &emsp;
![Spack](../images/package_managers/spack.svg){: style="height:1em"}&nbsp;[**Spack**](#spack) `nlohmann-json` &emsp;
[**Hunter**](#hunter) `nlohmann_json`<br>
![vcpkg](../images/package_managers/vcpkg.png){: style="height:1em"}&nbsp;[**vcpkg**](#vcpkg) `nlohmann-json` &emsp;
[**cget**](#cget) `nlohmann/json` &emsp;
![Swift Package Manager](../images/package_managers/swift.svg){: style="height:1em"}&nbsp;[**Swift Package Manager**](#swift-package-manager) `nlohmann/json`<br>
![Nuget](../images/package_managers/nuget.svg){: style="height:1em"}&nbsp;[**NuGet**](#nuget) `nlohmann.json` &emsp;
![Conda](../images/package_managers/conda.svg){: style="height:1em"}&nbsp;[**Conda**](#conda) `nlohmann_json` &emsp;
![MacPorts](../images/package_managers/macports.svg){: style="height:1em"}&nbsp;[**MacPorts**](#macports) `nlohmann-json`<br>
![cpm.cmake](../images/package_managers/CPM.png){: style="height:1em"}&nbsp;[**CPM.cmake**](#cpmcmake) `gh:nlohmann/json` &emsp;
![xmake](../images/package_managers/xmake.svg){: style="height:1em"}&nbsp;[**xmake**](#xmake) `nlohmann_json`
</p>
## Running example
Throughout this page, we will describe how to compile the example file `example.cpp` below.
```cpp
--8<-- "integration/example.cpp"
```
When executed, this program should create output similar to
```json
--8<-- "examples/meta.output"
```
## Homebrew
!!! abstract "Summary"
formula: [**`nlohmann-json`**](https://formulae.brew.sh/formula/nlohmann-json)
- [![Homebrew package](https://repology.org/badge/version-for-repo/homebrew/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
- :octicons-tag-24: Available versions: current version and development version (with `--HEAD` parameter)
- :octicons-rocket-24: The formula is updated with every release.
- :octicons-person-24: Maintainer: Niels Lohmann
- :octicons-file-24: File issues at the [Homebrew issue tracker](https://github.com/Homebrew/homebrew-core/issues)
- :octicons-question-24: [Homebrew website](https://brew.sh)
If you are using [Homebrew](http://brew.sh), you can install the library with
```sh
brew install nlohmann-json
```
The header can be used directly in your code or via CMake.
??? example "Example: Raw compilation"
1. Create the following file:
```cpp title="example.cpp"
--8<-- "integration/homebrew/example.cpp"
```
2. Install the package:
```sh
brew install nlohmann-json
```
3. Compile the code and pass the Homebrew prefix to the include path such that the library can be found:
```sh
c++ example.cpp -I$(brew --prefix nlohmann-json)/include -std=c++11 -o example
```
??? example "Example: CMake"
1. Create the following files:
```cpp title="example.cpp"
--8<-- "integration/homebrew/example.cpp"
```
```cmake title="CMakeLists.txt"
--8<-- "integration/homebrew/CMakeLists.txt"
```
2. Install the package:
```sh
brew install nlohmann-json
```
3. Compile the code and pass the Homebrew prefix to CMake to find installed packages via `#!cmake find_package`:
```sh
CMAKE_PREFIX_PATH=$(brew --prefix) cmake -S . -B build
cmake --build build
```
## Meson
!!! abstract "Summary"
wrap: **`nlohmann_json`**
- :octicons-tag-24: Available versions: current version and select older versions (see
[WrapDB](https://mesonbuild.com/Wrapdb-projects.html))
- :octicons-rocket-24: The package is updated automatically from file
[`meson.build`](https://github.com/nlohmann/json/blob/develop/meson.build).
- :octicons-file-24: File issues at the [library issue tracker](https://github.com/nlohmann/json/issues)
- :octicons-question-24: [Meson website](https://mesonbuild.com/index.html)
If you are using the [Meson Build System](http://mesonbuild.com), add this source tree as a [meson subproject](https://mesonbuild.com/Subprojects.html#using-a-subproject). You may also use the
`include.zip` published in this project's [Releases](https://github.com/nlohmann/json/releases) to reduce the size of the vendored source tree. Alternatively,
you can get a wrap file by downloading it from [Meson WrapDB](https://mesonbuild.com/Wrapdb-projects.html), or use
```shell
meson wrap install nlohmann_json
```
Please see the Meson project for any issues regarding the packaging.
The provided `meson.build` can also be used as an alternative to CMake for installing `nlohmann_json` system-wide in
which case a pkg-config file is installed. To use it, have your build system require the `nlohmann_json`
pkg-config dependency. In Meson, it is preferred to use the
[`dependency()`](https://mesonbuild.com/Reference-manual.html#dependency) object with a subproject fallback, rather than
using the subproject directly.
??? example "Example: Wrap"
1. Create the following files:
```ini title="meson.build"
--8<-- "integration/meson/meson.build"
```
```cpp title="example.cpp"
--8<-- "integration/meson/example.cpp"
```
2. Use the Meson WrapDB to fetch the nlohmann/json wrap:
```shell
mkdir subprojects
meson wrap install nlohmann_json
```
3. Build:
```shell
meson setup build
meson compile -C build
```
## Bazel
!!! abstract "Summary"
use `bazel_dep`, `git_override`, or `local_path_override`
- :octicons-tag-24: Any version, that is available via [Bazel Central Registry](https://registry.bazel.build/modules/nlohmann_json)
- :octicons-file-24: File issues at the [library issue tracker](https://github.com/nlohmann/json/issues)
- :octicons-question-24: [Bazel website](https://bazel.build)
This repository provides a [Bazel](https://bazel.build/) `MODULE.bazel` and a corresponding `BUILD.bazel` file. Therefore, this
repository can be referenced within a `MODULE.bazel` by rules such as `archive_override`, `git_override`, or `local_path_override`. To use the library, you need to depend on the target `@nlohmann_json//:json` (i.e., via `deps` attribute).
??? example
1. Create the following files:
```ini title="BUILD"
--8<-- "integration/bazel/BUILD"
```
```ini title="WORKSPACE"
--8<-- "integration/bazel/MODULE.bazel"
```
```cpp title="example.cpp"
--8<-- "integration/bazel/example.cpp"
```
2. Build and run:
```shell
bazel build //:main
bazel run //:main
```
## Conan
!!! abstract "Summary"
recipe: [**`nlohmann_json`**](https://conan.io/center/recipes/nlohmann_json)
- [![ConanCenter package](https://repology.org/badge/version-for-repo/conancenter/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
- :octicons-tag-24: Available versions: current version and older versions (see
[Conan Center](https://conan.io/center/recipes/nlohmann_json))
- :octicons-rocket-24: The package is updated automatically via
[this recipe](https://github.com/conan-io/conan-center-index/tree/master/recipes/nlohmann_json).
- :octicons-file-24: File issues at the [Conan Center issue tracker](https://github.com/conan-io/conan-center-index/issues)
- :octicons-question-24: [Conan website](https://conan.io)
If you are using [Conan](https://www.conan.io/) to manage your dependencies, merely add `nlohmann_json/x.y.z` to your `conanfile`'s
requires, where `x.y.z` is the release version you want to use.
??? example
1. Create the following files:
```ini title="Conanfile.txt"
--8<-- "integration/conan/Conanfile.txt"
```
```cmake title="CMakeLists.txt"
--8<-- "integration/conan/CMakeLists.txt"
```
```cpp title="example.cpp"
--8<-- "integration/conan/example.cpp"
```
2. Call Conan:
```sh
conan install . --output-folder=build --build=missing
```
3. Build:
```sh
cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE="conan_toolchain.cmake" -DCMAKE_BUILD_TYPE=Release
cmake --build build
```
## Spack
!!! abstract "Summary"
package: [**`nlohmann-json`**](https://packages.spack.io/package.html?name=nlohmann-json)
- [![Spack package](https://repology.org/badge/version-for-repo/spack/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
- :octicons-tag-24: Available versions: current version and older versions (see
[Spack package](https://packages.spack.io/package.html?name=nlohmann-json))
- :octicons-rocket-24: The package is updated with every release.
- :octicons-person-24: Maintainer: [Axel Huebl](https://github.com/ax3l)
- :octicons-file-24: File issues at the [Spack issue tracker](https://github.com/spack/spack/issues)
- :octicons-question-24: [Spack website](https://spack.io)
If you are using [Spack](https://www.spack.io/) to manage your dependencies, you can use the
[`nlohmann-json` package](https://packages.spack.io/package.html?name=nlohmann-json) via
```shell
spack install nlohmann-json
```
Please see the [Spack project](https://github.com/spack/spack) for any issues regarding the packaging.
??? example
1. Create the following files:
```cmake title="CMakeLists.txt"
--8<-- "integration/spack/CMakeLists.txt"
```
```cpp title="example.cpp"
--8<-- "integration/spack/example.cpp"
```
2. Install the library:
```sh
spack install nlohmann-json
```
3. Load the environment for your Spack-installed packages:
```sh
spack load nlohmann-json
```
4. Build the project with CMake:
```sh
cmake -S . -B build -DCMAKE_PREFIX_PATH=$(spack location -i nlohmann-json)
cmake --build build
```
## Hunter
!!! abstract "Summary"
package: [**`nlohmann_json`**](https://hunter.readthedocs.io/en/latest/packages/pkg/nlohmann_json.html)
- :octicons-tag-24: Available versions: current version and older versions (see
[Hunter package](https://hunter.readthedocs.io/en/latest/packages/pkg/nlohmann_json.html))
- :octicons-rocket-24: The package is updated with every release.
- :octicons-file-24: File issues at the [Hunter issue tracker](https://github.com/cpp-pm/hunter/issues)
- :octicons-question-24: [Hunter website](https://hunter.readthedocs.io/en/latest/)
If you are using [Hunter](https://github.com/cpp-pm/hunter) on your project for external dependencies, then you can use
the [nlohmann_json package](https://hunter.readthedocs.io/en/latest/packages/pkg/nlohmann_json.html) via
```cmake
hunter_add_package(nlohmann_json)
```
Please see the Hunter project for any issues regarding the packaging.
??? example
1. Create the following files:
```cmake title="CMakeLists.txt"
--8<-- "integration/hunter/CMakeLists.txt"
```
```cpp title="example.cpp"
--8<-- "integration/hunter/example.cpp"
```
2. Download required files
```shell
mkdir cmake
wget https://raw.githubusercontent.com/cpp-pm/gate/master/cmake/HunterGate.cmake -O cmake/HunterGate.cmake
```
3. Build the project with CMake:
```shell
cmake -S . -B build
cmake --build build
```
## vcpkg
!!! abstract "Summary"
package: [**`nlohmann-json`**](https://github.com/Microsoft/vcpkg/tree/master/ports/nlohmann-json)
- [![Vcpkg package](https://repology.org/badge/version-for-repo/vcpkg/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
- :octicons-tag-24: Available versions: current version
- :octicons-rocket-24: The package is updated with every release.
- :octicons-file-24: File issues at the [vcpkg issue tracker](https://github.com/microsoft/vcpkg/issues)
- :octicons-question-24: [vcpkg website](https://vcpkg.io/)
If you are using [vcpkg](https://github.com/Microsoft/vcpkg/) on your project for external dependencies, then you can
install the [nlohmann-json package](https://github.com/Microsoft/vcpkg/tree/master/ports/nlohmann-json) with
```shell
vcpkg install nlohmann-json
```
and follow the then displayed descriptions. Please see the vcpkg project for any issues regarding the packaging.
??? example
1. Create the following files:
```cmake title="CMakeLists.txt"
--8<-- "integration/vcpkg/CMakeLists.txt"
```
```cpp title="example.cpp"
--8<-- "integration/vcpkg/example.cpp"
```
2. Install package:
```sh
vcpkg install nlohmann-json
```
3. Build:
```sh
cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=$VCPKG_ROOT/scripts/buildsystems/vcpkg.cmake
cmake --build build
```
## cget
!!! abstract "Summary"
package: [**`nlohmann/json`**](https://github.com/pfultz2/cget-recipes/blob/master/recipes/nlohmann/json/package.txt)
- :octicons-tag-24: Available versions: current version and older versions
- :octicons-rocket-24: The package is updated with every release.
- :octicons-file-24: File issues at the [cget issue tracker](https://github.com/pfultz2/cget-recipes/issues)
- :octicons-question-24: [cget website](https://cget.readthedocs.io/)
If you are using [cget](http://cget.readthedocs.io/en/latest/), you can install the latest `master` version with
```shell
cget install nlohmann/json
```
A specific version can be installed with `cget install nlohmann/json@v3.12.0`. Also, the multiple header version can be
installed by adding the `-DJSON_MultipleHeaders=ON` flag (i.e., `cget install nlohmann/json -DJSON_MultipleHeaders=ON`).
??? example
1. Create the following files:
```cmake title="CMakeLists.txt"
--8<-- "integration/vcpkg/CMakeLists.txt"
```
```cpp title="example.cpp"
--8<-- "integration/vcpkg/example.cpp"
```
2. Initialize cget
```shell
cget init
```
3. Install the library
```shell
cget install nlohmann/json
```
4. Build
```shell
cmake -S . -B build -DCMAKE_TOOLCHAIN_FILE=cget/cget/cget.cmake
cmake --build build
```
## Swift Package Manager
!!! abstract "Summary"
package: **`nlohmann/json`**
- :octicons-tag-24: Available versions: current version and older versions
- :octicons-rocket-24: The package is updated with every release.
- :octicons-file-24: File issues at the [library issue tracker](https://github.com/nlohmann/json/issues)
- :octicons-question-24: [Xcode documentation](https://developer.apple.com/documentation/xcode/adding-package-dependencies-to-your-app)
## NuGet
!!! abstract "Summary"
package: [**`nlohmann.json`**](https://www.nuget.org/packages/nlohmann.json/)
- :octicons-tag-24: Available versions: current and previous versions
- :octicons-rocket-24: The package is updated with every release.
- :octicons-person-24: Maintainer: [Hani Kaabi](https://github.com/hnkb)
- :octicons-file-24: File issues at the [maintainer's issue tracker](https://github.com/hnkb/nlohmann-json-nuget/issues)
- :octicons-question-24: [NuGet website](https://www.nuget.org)
If you are using [NuGet](https://www.nuget.org), you can use the package [nlohmann.json](https://www.nuget.org/packages/nlohmann.json/)
with
```shell
dotnet add package nlohmann.json
```
??? example
Probably the easiest way to use NuGet packages is through Visual Studio graphical interface. Right-click on a
project (any C++ project would do) in “Solution Explorer” and select “Manage NuGet Packages…”
![](nuget/nuget-search-package.png)
Now you can click on “Browse” tab and find the package you like to install.
![](nuget/nuget-select-package.png)
Most of the packages in NuGet gallery are .NET packages and would not be useful in a C++ project. Microsoft
recommends adding “native” and “nativepackage” tags to C++ NuGet packages to distinguish them, but even adding
“native” to search query would still show many .NET-only packages in the list.
Nevertheless, after finding the package you want, click on “Install” button and accept confirmation dialogs.
After the package is successfully added to the projects, you should be able to build and execute the project
without the need for making any more changes to build settings.
!!! note
A few notes:
- NuGet packages are installed per project and not system-wide. The header and binaries for the package are only
available to the project it is added to, and not other projects (obviously unless we add the package to those
projects as well)
- One of the many great things about your elegant work is that it is a header-only library, which makes
deployment very straightforward. In case of libraries which need binary deployment (`.lib`, `.dll` and `.pdb`
for debug info) the different binaries for each supported compiler version must be added to the NuGet package.
Some library creators cram binary versions for all supported Visual C++ compiler versions in the same package,
so a single package will support all compilers. Some others create a different package for each compiler
version (and you usually see things like “v140” or “vc141” in package name to clarify which VC++ compiler this
package supports).
- Packages can have dependency to other packages, and in this case, NuGet will install all dependencies as well
as the requested package recursively.
**What happens behind the scenes**
After you add a NuGet package, three changes occur in the project source directory. Of course, we could make these
changes manually instead of using GUI:
![](nuget/nuget-project-changes.png)
1. A `packages.config` file will be created (or updated to include the package name if one such file already
exists). This file contains a list of the packages required by this project (name and minimum version) and must
be added to the project source code repository, so if you move the source code to a new machine, MSBuild/NuGet
knows which packages it has to restore (which it does automatically before each build).
```xml
<?xml version="1.0" encoding="utf-8"?>
<packages>
<package id="nlohmann.json" version="3.5.0" targetFramework="native" />
</packages>
```
2. A `packages` folder which contains actual files in the packages (these are header and binary files required for
a successful build, plus a few metadata files). In case of this library for example, it contains `json.hpp`:
![](nuget/nuget-package-content.png)
!!! note
This directory should not be added to the project source code repository, as it will be restored before each
build by MSBuild/NuGet. If you go ahead and delete this folder, then build the project again, it will
magically re-appear!
3. Project MSBuild makefile (which for Visual C++ projects has a .vcxproj extension) will be updated to include
settings from the package.
![](nuget/nuget-project-makefile.png)
The important bit for us here is line 170, which tells MSBuild to import settings from
`packages\nlohmann.json.3.5.0\build\native\nlohmann.json.targets` file. This is a file the package creator
created and added to the package (you can see it is one of the two files I created in this repository, the other
just contains package attributes like name and version number). What does it contain?
For our header-only repository, the only setting we need is to add our include directory to the list of
`AdditionalIncludeDirectories`:
```xml
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<ItemDefinitionGroup>
<ClCompile>
<AdditionalIncludeDirectories>$(MSBuildThisFileDirectory)include;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
</ClCompile>
</ItemDefinitionGroup>
</Project>
```
For libraries with binary files, we will need to add `.lib` files to linker inputs and add settings to copy
`.dll` and other redistributable files to output directory, if needed.
There are other changes to the makefile as well:
- Lines 165-167 add the `packages.config` as one of project files (so it is shown in Solution Explorer tree
view). It is added as None (no build action) and removing it wouldn’t affect build.
- Lines 172-177 check to ensure the required packages are present. This will display a build error if package
directory is empty (for example when NuGet cannot restore packages because Internet connection is down).
Again, if you omit this section, the only change in build would be a more cryptic error message if build
fails.
!!! note
Changes to .vcxproj makefile should also be added to project source code repository.
As you can see, the mechanism NuGet uses to modify project settings is through MSBuild makefiles, so using NuGet
with other build systems and compilers (like CMake) as a dependency manager is either impossible or more problematic
than useful.
Please refer to [this extensive description](https://github.com/nlohmann/json/issues/1132#issuecomment-452250255) for
more information.
## Conda
!!! abstract "Summary"
package: [**`nlohmann_json`**](https://anaconda.org/conda-forge/nlohmann_json)
- ![](https://img.shields.io/conda/v/conda-forge/nlohmann_json)
- :octicons-tag-24: Available versions: current and previous versions
- :octicons-rocket-24: The package is updated with every release.
- :octicons-file-24: File issues at the [feedstock's issue tracker](https://github.com/conda-forge/nlohmann_json-feedstock/issues)
- :octicons-question-24: [Conda documentation](https://docs.conda.io/projects/conda/en/stable/user-guide/getting-started.html)
If you are using [conda](https://conda.io/), you can use the package
[nlohmann_json](https://anaconda.org/conda-forge/nlohmann_json) from [conda-forge](https://conda-forge.org) executing
```shell
conda install -c conda-forge nlohmann_json
```
??? example
1. Create the following file:
```cpp title="example.cpp"
--8<-- "integration/conda/example.cpp"
```
2. Create and activate an environment `json`:
```shell
conda create -n json
conda activate json
```
3. Install the package:
```shell
conda install -c conda-forge nlohmann_json
```
4. Build the code:
```shell
g++ -std=c++11 -I$(conda info --base)/envs/json/include example.cpp -o example
```
## MSYS2
If you are using [MSYS2](http://www.msys2.org/), you can use the [mingw-w64-nlohmann-json](https://packages.msys2.org/base/mingw-w64-nlohmann-json) package, type `pacman -S mingw-w64-i686-nlohmann-json` or `pacman -S mingw-w64-x86_64-nlohmann-json` for installation. Please file issues [here](https://github.com/msys2/MINGW-packages/issues/new?title=%5Bnlohmann-json%5D) if you experience problems with the packages.
[![MSYS2 clang64 package](https://repology.org/badge/version-for-repo/msys2_clang64/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
[![MSYS2 clangarm64 package](https://repology.org/badge/version-for-repo/msys2_clangarm64/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
[![MSYS2 mingw package](https://repology.org/badge/version-for-repo/msys2_mingw/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
[![MSYS2 ucrt64 package](https://repology.org/badge/version-for-repo/msys2_ucrt64/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
:material-update: The [package](https://packages.msys2.org/base/mingw-w64-nlohmann-json) is updated automatically.
## MacPorts
!!! abstract "Summary"
port: [**`nlohmann-json`**](https://ports.macports.org/port/nlohmann-json/)
- [![MacPorts package](https://repology.org/badge/version-for-repo/macports/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
- :octicons-tag-24: Available versions: current version
- :octicons-rocket-24: The port is updated with every release.
- :octicons-file-24: File issues at the [MacPorts issue tracker](https://trac.macports.org/newticket?port=nlohmann-json)
- :octicons-question-24: [MacPorts website](https://www.macports.org)
If you are using [MacPorts](https://ports.macports.org), execute
```shell
sudo port install nlohmann-json
```
to install the [nlohmann-json](https://ports.macports.org/port/nlohmann-json/) package.
??? example "Example: Raw compilation"
1. Create the following file:
```cpp title="example.cpp"
--8<-- "integration/macports/example.cpp"
```
2. Install the package:
```sh
sudo port install nlohmann-json
```
3. Compile the code and pass the MacPorts prefix to the include path such that the library can be found:
```sh
c++ example.cpp -I/opt/local/include -std=c++11 -o example
```
??? example "Example: CMake"
1. Create the following files:
```cpp title="example.cpp"
--8<-- "integration/homebrew/example.cpp"
```
```cmake title="CMakeLists.txt"
--8<-- "integration/homebrew/CMakeLists.txt"
```
2. Install the package:
```sh
sudo port install nlohmann-json
```
3. Compile the code:
```sh
cmake -S . -B build
cmake --build build
```
## build2
!!! abstract "Summary"
package: **`nlohmann-json`**
library target: **`nlohmann-json%lib{json}`**
available in package repositories:
- [`cppget.org` (recommended)](https://cppget.org/nlohmann-json)
- [package's sources (for advanced users)](https://github.com/build2-packaging/nlohmann-json/)
- :octicons-tag-24: Available versions: current version and older versions since `3.7.3` (see [cppget.org](https://cppget.org/nlohmann-json))
- :octicons-rocket-24: The package is maintained and published by the `build2` community in [this repository](https://github.com/build2-packaging/nlohmann-json/).
- :octicons-file-24: File issues at the [package source repository](https://github.com/build2-packaging/nlohmann-json/issues/)
- :octicons-question-24: [`build2` website](https://build2.org)
Note: [`build2`](https://build2.org) should not be considered as a standalone package-manager. It is a build-system + package manager + project manager, a set of tools that work hand-in-hand. `build2`-based projects do not rely on existing `CMake` scripts and the build scripts defining the project's targets are specific to `build2`.
To use this package in an existing [`build2`](https://build2.org) project, the general steps are:
1. <details><summary>Make the package available to download from a package repository that provides it.</summary>
Your project's `repositories.manifest` specifies where the package manager will try to acquire packages by default. Make sure one of the repositories specified in this file provides `nlohmann-json` package.
The recommended open-source repository is [`cppget.org`](https://cppget.org/).
If the project has been created using [`bdep new`](https://build2.org/bdep/doc/bdep-new.xhtml), `cppget.org` is already specified in `repositories.manifest` but commented, just uncomment these lines:
```
:
role: prerequisite
location: https://pkg.cppget.org/1/stable
```
</details>
2. <details><summary>Add this package as dependency of your project.</summary>
In your project's `manifest` add the dependency to the package using `depends: nlohmann-json`. You could also add some [version constraints](https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml#guide-add-remove-deps).
For example, to depend on the latest version available:
```
depends: nlohmann-json
```
</details>
3. <details><summary>Add this library as dependency of your target that uses it.</summary>
In the `buildfile` defining the target that will use this library:
- import the target `lib{json}` from the `nlohmann-json` package, for example:
```
import nljson = nlohmann-json%lib{json}
```
- then add the library's target as requirement for your target using it, for example:
```
exe{example} : ... $nljson
```
</details>
4. <details><summary>Use the library in your project's code and build it.</summary>
At this point, assuming your project is initialized in a build-configuration, any `b` or `bdep update` command that will update/build the project will also acquire the missing dependency automatically, then build it and link it with your target.
If you just want to synchronize dependencies for all your configurations to download the ones you just added:
```
bdep sync -af
```
</details>
??? example "Example: from scratch, using `build2`'s [`bdep new` command](https://build2.org/bdep/doc/bdep-new.xhtml)"
1. Create a new executable project "example" (see [`bdep new` command details](https://build2.org/bdep/doc/bdep-new.xhtml) for the various options to create a new project):
```shell
bdep new example
```
2. Edit these files by replacing their content:
- `example/repositories.manifest`: Enable acquiring packages from https://cppget.org by uncommenting the related lines:
```make title="project's `repositories.manifest`"
--8<-- "integration/build2/repositories.manifest"
```
- `example/manifest`: Add the latest version of the `nlohmann-json` package as dependency to the project:
```make title="project's `manifest`"
--8<-- "integration/build2/manifest"
```
- `example/example/buildfile`: import the library's target to be used as requirement for building the executable target `exe{example}`:
```make title="project's `buildfile`"
--8<-- "integration/build2/buildfile"
```
- `example/example/example.cxx`: `bdep new` generates a "hello world" by default, replace it by this:
```cpp title="example.cxx"
--8<-- "integration/build2/example.cpp"
```
- `example/example/testscript`: (optional) if you want to be able to test that executable's output is correct using `b test`:
```cpp title="`testscript` checking the output of the program"
--8<-- "integration/build2/testscript"
```
3. Initialize the project in a default C/C++ build configuration directory, then build and test:
```shell
cd example/
# create default C/C++ build configuration in ../example-myconfig/, initialize the project in it (downloads it's dependencies in it too)
bdep init -C @myconfig cc
# build only,
b
# or build and test the executable's output, will only work if the `testscript` is correct
b test
```
## CPM.cmake
!!! abstract "Summary"
package: **`gh:nlohmann/json`**
- :octicons-tag-24: Available versions: current and previous versions
- :octicons-rocket-24: The package is updated with every release.
- :octicons-file-24: File issues at the [CPM.cmake issue tracker](https://github.com/cpm-cmake/CPM.cmake/issues)
- :octicons-question-24: [CPM.cmake website](https://github.com/cpm-cmake/CPM.cmake)
If you are using [`CPM.cmake`](https://github.com/TheLartians/CPM.cmake), add the
[CPM.cmake script](https://github.com/TheLartians/CPM.cmake#adding-cpm) and the following snippet to your CMake project:
```cmake
CPMAddPackage("gh:nlohmann/json@3.12.0")
```
??? example
1. Create the following files:
```cpp title="example.cpp"
--8<-- "integration/cpm/example.cpp"
```
```cmake title="CMakeLists.txt"
--8<-- "integration/cpm/CMakeLists.txt"
```
2. Download CPM.cmake
```shell
mkdir -p cmake
wget -O cmake/CPM.cmake https://github.com/cpm-cmake/CPM.cmake/releases/latest/download/get_cpm.cmake
```
3. Build
```shell
cmake -S . -B build
cmake --build build
```
## xmake
!!! abstract "Summary"
package: [**`nlohmann_json`**](https://github.com/xmake-io/xmake-repo/blob/master/packages/n/nlohmann_json/xmake.lua)
- :octicons-tag-24: Available versions: current and previous versions
- :octicons-rocket-24: The package is updated with every release.
- :octicons-file-24: File issues at the [xmake issue tracker](https://github.com/xmake-io/xmake-repo/issues)
- :octicons-question-24: [xmake website](https://xmake.io/#/)
??? example
1. Create the following files:
```cpp title="example.cpp"
--8<-- "integration/xmake/example.cpp"
```
```lua title="xmake.lua"
--8<-- "integration/xmake/xmake.lua"
```
2. Build
```shell
xmake
```
3. Run
```shell
xmake run
```
* * *
## Other package managers
The library is also contained in many other package repositories: [![Packaging status](https://repology.org/badge/tiny-repos/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
??? example "Package version overview"
[![Packaging status](https://repology.org/badge/vertical-allrepos/nlohmann-json.svg)](https://repology.org/project/nlohmann-json/versions)
* * *
## Buckaroo
If you are using [Buckaroo](https://buckaroo.pm), you can install this library's module with `buckaroo add github.com/buckaroo-pm/nlohmann-json`. There is a demo repo [here](https://github.com/njlr/buckaroo-nholmann-json-example).
!!! warning
The module is outdated as the respective [repository](https://github.com/buckaroo-pm/nlohmann-json) has not been
updated in years.
## CocoaPods
If you are using [CocoaPods](https://cocoapods.org), you can use the library by adding pod `"nlohmann_json", '~>3.1.2'`
to your podfile (see [an example](https://bitbucket.org/benman/nlohmann_json-cocoapod/src/master/)). Please file issues
[here](https://bitbucket.org/benman/nlohmann_json-cocoapod/issues?status=new&status=open).
![](https://img.shields.io/cocoapods/v/nlohmann_json)
!!! warning
The module is outdated as the respective [pod](https://cocoapods.org/pods/nlohmann_json) has not been updated in years.
integration/package_managers/index.html
+1 -1
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@@ -416,4 +416,4 @@ cmake<span class=w> </span>--build<span class=w> </span>build
<span class=w> </span><span class=nf>set_languages</span><span class=p>(</span><span class=s2>&quot;cxx11&quot;</span><span class=p>)</span>
</code></pre></div> </li> <li> <p>Build</p> <div class=highlight><pre><span></span><code>xmake
</code></pre></div> </li> <li> <p>Run</p> <div class=highlight><pre><span></span><code>xmake<span class=w> </span>run
</code></pre></div> </li> </ol> </details> <hr> <h2 id=other-package-managers>Other package managers<a class=headerlink href=#other-package-managers title="Permanent link">&para;</a></h2> <p>The library is also contained in many other package repositories: <a href="https://repology.org/project/nlohmann-json/versions"><img alt="Packaging status" src="../../assets/external/repology.org/badge/tiny-repos/nlohmann-json.svg"></a></p> <details class=example> <summary>Package version overview</summary> <p><a href="https://repology.org/project/nlohmann-json/versions"><img alt="Packaging status" src="../../assets/external/repology.org/badge/vertical-allrepos/nlohmann-json.svg"></a></p> </details> <hr> <h2 id=buckaroo>Buckaroo<a class=headerlink href=#buckaroo title="Permanent link">&para;</a></h2> <p>If you are using <a href="https://buckaroo.pm">Buckaroo</a>, you can install this library's module with <code>buckaroo add github.com/buckaroo-pm/nlohmann-json</code>. There is a demo repo <a href="https://github.com/njlr/buckaroo-nholmann-json-example">here</a>.</p> <div class="admonition warning"> <p class=admonition-title>Warning</p> <p>The module is outdated as the respective <a href="https://github.com/buckaroo-pm/nlohmann-json">repository</a> has not been updated in years.</p> </div> <h2 id=cocoapods>CocoaPods<a class=headerlink href=#cocoapods title="Permanent link">&para;</a></h2> <p>If you are using <a href="https://cocoapods.org">CocoaPods</a>, you can use the library by adding pod <code>"nlohmann_json", '~&gt;3.1.2'</code> to your podfile (see <a href="https://bitbucket.org/benman/nlohmann_json-cocoapod/src/master/">an example</a>). Please file issues <a href="https://bitbucket.org/benman/nlohmann_json-cocoapod/issues?status=new&amp;status=open">here</a>.</p> <p><img alt src="../../assets/external/img.shields.io/cocoapods/v/nlohmann_json.svg"></p> <div class="admonition warning"> <p class=admonition-title>Warning</p> <p>The module is outdated as the respective <a href="https://cocoapods.org/pods/nlohmann_json">pod</a> has not been updated in years.</p> </div> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 4, 2026 09:13:25 UTC">July 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.Line truncated
</code></pre></div> </li> </ol> </details> <hr> <h2 id=other-package-managers>Other package managers<a class=headerlink href=#other-package-managers title="Permanent link">&para;</a></h2> <p>The library is also contained in many other package repositories: <a href="https://repology.org/project/nlohmann-json/versions"><img alt="Packaging status" src="../../assets/external/repology.org/badge/tiny-repos/nlohmann-json.svg"></a></p> <details class=example> <summary>Package version overview</summary> <p><a href="https://repology.org/project/nlohmann-json/versions"><img alt="Packaging status" src="../../assets/external/repology.org/badge/vertical-allrepos/nlohmann-json.svg"></a></p> </details> <hr> <h2 id=buckaroo>Buckaroo<a class=headerlink href=#buckaroo title="Permanent link">&para;</a></h2> <p>If you are using <a href="https://buckaroo.pm">Buckaroo</a>, you can install this library's module with <code>buckaroo add github.com/buckaroo-pm/nlohmann-json</code>. There is a demo repo <a href="https://github.com/njlr/buckaroo-nholmann-json-example">here</a>.</p> <div class="admonition warning"> <p class=admonition-title>Warning</p> <p>The module is outdated as the respective <a href="https://github.com/buckaroo-pm/nlohmann-json">repository</a> has not been updated in years.</p> </div> <h2 id=cocoapods>CocoaPods<a class=headerlink href=#cocoapods title="Permanent link">&para;</a></h2> <p>If you are using <a href="https://cocoapods.org">CocoaPods</a>, you can use the library by adding pod <code>"nlohmann_json", '~&gt;3.1.2'</code> to your podfile (see <a href="https://bitbucket.org/benman/nlohmann_json-cocoapod/src/master/">an example</a>). Please file issues <a href="https://bitbucket.org/benman/nlohmann_json-cocoapod/issues?status=new&amp;status=open">here</a>.</p> <p><img alt src="../../assets/external/img.shields.io/cocoapods/v/nlohmann_json.svg"></p> <div class="admonition warning"> <p class=admonition-title>Warning</p> <p>The module is outdated as the respective <a href="https://cocoapods.org/pods/nlohmann_json">pod</a> has not been updated in years.</p> </div> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 8, 2026 18:18:24 UTC">July 8, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 2013-2026 Niels Lohmann </div> </div> <div class=md-social> <a href="https://github.com/nlohmann" target="_blank" rel="noopener" title="github.com" class="md-social__link"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 512 512"><!-- Font Awesome Free 7.1.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2025 Fonticons, Inc.--><path d="M173.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6m-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3m44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9M252.8 8C114.1 8 8 113.3 8 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.Line truncated
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# Pkg-config
If you are using bare Makefiles, you can use `pkg-config` to generate the include flags that point to where the library is installed:
```sh
pkg-config nlohmann_json --cflags
```
Users of the [Meson build system](package_managers.md#meson) will also be able to use a system-wide library, which will be found by `pkg-config`:
```meson
json = dependency('nlohmann_json', required: true)
```
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<!doctype html><html lang=en class=no-js> <head><meta charset=utf-8><meta name=viewport content="width=device-width,initial-scale=1"><meta name=author content="Niels Lohmann"><link href="https://json.nlohmann.me/integration/pkg-config/" rel="canonical"><link href=../package_managers/ rel=prev><link href=../../api/basic_json/ rel=next><link rel=icon href=../../assets/images/favicon.png><meta name=generator content="mkdocs-1.6.1, mkdocs-material-9.7.6"><title>Pkg-config - JSON for Modern C++</title><link rel=stylesheet href=../../assets/stylesheets/main.484c7ddc.min.css><link rel=stylesheet href=../../assets/stylesheets/palette.ab4e12ef.min.css><link rel="stylesheet" href="../../assets/external/fonts.googleapis.com/css.61a430c9.css"><style>:root{--md-text-font:"Roboto";--md-code-font:"JetBrains Mono"}</style><link rel=stylesheet href=../../css/custom.css><script>__md_scope=new URL("../..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script></head> <body dir=ltr data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo> <input class=md-toggle data-md-toggle=drawer type=checkbox id=__drawer autocomplete=off> <input class=md-toggle data-md-toggle=search type=checkbox id=__search autocomplete=off> <label class=md-overlay for=__drawer></label> <div data-md-component=skip> <a href=#pkg-config class=md-skip> Skip to content </a> </div> <div data-md-component=announce> </div> <header class=md-header data-md-component=header> <nav class="md-header__inner md-grid" aria-label=Header> <a href=../.. title="JSON for Modern C++" class="md-header__button md-logo" aria-label="JSON for Modern C++" data-md-component=logo> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M12 8a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3 3 3 0 0 0 3 3m0 3.54C9.64 9.35 6.5 8 3 8v11c3.5 0 6.64 1.35 9 3.54 2.36-2.19 5.5-3.54 9-3.54V8c-3.5 0-6.64 1.35-9 3.54"/></svg> </a> <label class="md-header__button md-icon" for=__drawer> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class=md-header__title data-md-component=header-title> <div class=md-header__ellipsis> <div class=md-header__topic> <span class=md-ellipsis> JSON for Modern C++ </span> </div> <div class=md-header__topic data-md-component=header-topic> <span class=md-ellipsis> Pkg-config </span> </div> </div> </div> <form class=md-header__option data-md-component=palette> <input class=md-option data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme=default data-md-color-primary=indigo data-md-color-accent=indigo aria-label="Switch to dark mode" type=radio 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</code></pre></div> <p>Users of the <a href=../package_managers/#meson>Meson build system</a> will also be able to use a system-wide library, which will be found by <code>pkg-config</code>:</p> <div class=highlight><pre><span></span><code><span class=n>json</span><span class=w> </span><span class=o>=</span><span class=w> </span><span class=nb>dependency</span><span class=p>(</span><span class=s>&#39;nlohmann_json&#39;</span><span class=p>,</span><span class=w> </span><span class=n>required</span><span class=p>:</span><span class=w> </span><span class=kc>true</span><span class=p>)</span>
</code></pre></div> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 4, 2026 09:13:25 UTC">July 4, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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</code></pre></div> <!-- https://squidfunk.github.io/mkdocs-material/reference/tooltips/#adding-a-glossary --> <aside class=md-source-file> <span class=md-source-file__fact> <span class=md-icon title="Last update"> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M21 13.1c-.1 0-.3.1-.4.2l-1 1 2.1 2.1 1-1c.2-.2.2-.6 0-.8l-1.3-1.3c-.1-.1-.2-.2-.4-.2m-1.9 1.8-6.1 6V23h2.1l6.1-6.1zM12.5 7v5.2l4 2.4-1 1L11 13V7zM11 21.9c-5.1-.5-9-4.8-9-9.9C2 6.5 6.5 2 12 2c5.3 0 9.6 4.1 10 9.3-.3-.1-.6-.2-1-.2s-.7.1-1 .2C19.6 7.2 16.2 4 12 4c-4.4 0-8 3.6-8 8 0 4.1 3.1 7.5 7.1 7.9l-.1.2z"/></svg> </span> <span class="git-revision-date-localized-plugin git-revision-date-localized-plugin-date" title="July 8, 2026 18:18:24 UTC">July 8, 2026</span> </span> </aside> </article> </div> <script>var tabs=__md_get("__tabs");if(Array.isArray(tabs))e:for(var set of document.querySelectorAll(".tabbed-set")){var labels=set.querySelector(".tabbed-labels");for(var tab of tabs)for(var label of labels.getElementsByTagName("label"))if(label.innerText.trim()===tab){var input=document.getElementById(label.htmlFor);input.checked=!0;continue e}}</script> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type=button class="md-top md-icon" data-md-component=top hidden> <svg xmlns=http://www.w3.org/2000/svg viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top </button> </main> <footer class=md-footer> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class=md-copyright> <div class=md-copyright__highlight> Copyright &copy; 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integration/pkg-config/index.md
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# Pkg-config
If you are using bare Makefiles, you can use `pkg-config` to generate the include flags that point to where the library is installed:
```
pkg-config nlohmann_json --cflags
```
Users of the [Meson build system](https://json.nlohmann.me/integration/package_managers/#meson) will also be able to use a system-wide library, which will be found by `pkg-config`:
```
json = dependency('nlohmann_json', required: true)
```