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Throughout this page, we will describe how to compile the example file example.cpp below.

#include <nlohmann/json.hpp>
#include <iostream>
#include <iomanip>

using json = nlohmann::json;

int main()
{
    std::cout << std::setw(4) << json::meta() << std::endl;
}

When executed, this program should create output similar to

{
    "compiler": {
        "c++": "201103",
        "family": "gcc",
        "version": "12.3.0"
    },
    "copyright": "(C) 2013-2022 Niels Lohmann",
    "name": "JSON for Modern C++",
    "platform": "apple",
    "url": "https://github.com/nlohmann/json",
    "version": {
        "major": 3,
        "minor": 11,
        "patch": 3,
        "string": "3.11.3"
    }
}

Homebrew

If you are using OS X and Homebrew, just type

brew install nlohmann-json

and you're set. If you want the bleeding edge rather than the latest release, use

brew install nlohmann-json --HEAD

instead. See nlohmann-json for more information.

Example

  1. Create the following file:

    example.cpp
    #include <nlohmann/json.hpp>
#include <iostream>
#include <iomanip>

using json = nlohmann::json;

int main()
{
    std::cout << std::setw(4) << json::meta() << std::endl;
}

  2. Install the package

    brew install nlohmann-json

  3. Determine the include path, which defaults to /usr/local/Cellar/nlohmann-json/$version/include, where $version is the version of the library, e.g. 3.7.3. The path of the library can be determined with

    brew list nlohmann-json

  4. Compile the code. For instance, the code can be compiled using Clang with

    clang++ example.cpp -I/usr/local/Cellar/nlohmann-json/3.7.3/include -std=c++11 -o example

The formula is updated automatically.

Meson

If you are using the Meson Build System, add this source tree as a meson subproject. You may also use the include.zip published in this project's Releases to reduce the size of the vendored source tree. Alternatively, you can get a wrap file by downloading it from Meson WrapDB, or simply use 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, simply have your build system require the nlohmann_json pkg-config dependency. In Meson, it is preferred to use the dependency() object with a subproject fallback, rather than using the subproject directly.

Bazel

This repository provides a Bazel WORKSPACE.bazel and a corresponding BUILD.bazel file. Therefore, this repository can be referenced by workspace rules such as http_archive, git_repository, or local_repository from other Bazel workspaces. To use the library you only need to depend on the target @nlohmann_json//:json (e.g. via deps attribute).

Conan

If you are using Conan 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. Please file issues here if you experience problems with the packages.

Example

  1. Create the following files:

    Conanfile.txt
    [requires]
nlohmann_json/3.7.3

[generators]
cmake
    CMakeLists.txt
    project(json_example)
cmake_minimum_required(VERSION 2.8.12)
add_definitions("-std=c++11")

include(${CMAKE_BINARY_DIR}/conanbuildinfo.cmake)
conan_basic_setup()

add_executable(json_example example.cpp)
target_link_libraries(json_example ${CONAN_LIBS})
    example.cpp
    #include <nlohmann/json.hpp>
#include <iostream>

using json = nlohmann::json;

int main()
{
    std::cout << json::meta() << std::endl;
}

  2. Build:

    mkdir build
cd build
conan install ..
cmake ..
cmake --build .

The package is updated automatically.

Spack

If you are using Spack to manage your dependencies, you can use the nlohmann-json package. Please see the spack project for any issues regarding the packaging.

Hunter

If you are using hunter on your project for external dependencies, then you can use the nlohmann_json package. Please see the hunter project for any issues regarding the packaging.

Buckaroo

If you are using Buckaroo, you can install this library's module with buckaroo add github.com/buckaroo-pm/nlohmann-json. Please file issues here. There is a demo repo here.

vcpkg

If you are using vcpkg on your project for external dependencies, then you can install the nlohmann-json package with 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:

    CMakeLists.txt
    project(json_example)
cmake_minimum_required(VERSION 2.8.12)

find_package(nlohmann_json CONFIG REQUIRED)

add_executable(json_example example.cpp)
target_link_libraries(json_example PRIVATE nlohmann_json::nlohmann_json)
    example.cpp
    #include <nlohmann/json.hpp>
#include <iostream>

using json = nlohmann::json;

int main()
{
    std::cout << json::meta() << std::endl;
}

  2. Install package:

    vcpkg install nlohmann-json

  3. Build:

    mkdir build
cd build
cmake .. -DCMAKE_TOOLCHAIN_FILE=/path/to/vcpkg/scripts/buildsystems/vcpkg.cmake
cmake --build .

Note you need to adjust /path/to/vcpkg/scripts/buildsystems/vcpkg.cmake to your system.

cget

If you are using cget, you can install the latest development version with cget install nlohmann/json. A specific version can be installed with cget install nlohmann/json@v3.1.0. Also, the multiple header version can be installed by adding the -DJSON_MultipleHeaders=ON flag (i.e., cget install nlohmann/json -DJSON_MultipleHeaders=ON).

cget reads directly from the GitHub repository and is always up-to-date.

CocoaPods

If you are using CocoaPods, you can use the library by adding pod "nlohmann_json", '~>3.1.2' to your podfile (see an example). Please file issues here.

NuGet

If you are using NuGet, you can use the package nlohmann.json. Please check this extensive description on how to use the package. Please file issues here.

Conda

If you are using conda, you can use the package nlohmann_json from conda-forge executing conda install -c conda-forge nlohmann_json. Please file issues here.

MSYS2

If you are using MSYS2, you can use the mingw-w64-nlohmann-json package, just type pacman -S mingw-w64-i686-nlohmann-json or pacman -S mingw-w64-x86_64-nlohmann-json for installation. Please file issues here if you experience problems with the packages.

The package is updated automatically.

MacPorts

If you are using MacPorts, execute sudo port install nlohmann-json to install the nlohmann-json package.

The package is updated automatically.

build2

If you are using build2, you can use the nlohmann-json package from the public repository http://cppget.org or directly from the package's sources repository. In your project's manifest file, just add depends: nlohmann-json (probably with some version constraints). If you are not familiar with using dependencies in build2, please read this introduction. Please file issues here if you experience problems with the packages.

The package is updated automatically.

wsjcpp

If you are using wsjcpp, you can use the command wsjcpp install "https://github.com/nlohmann/json:develop" to get the latest version. Note you can change the branch ":develop" to an existing tag or another branch.

wsjcpp reads directly from the GitHub repository and is always up-to-date.

CPM.cmake

If you are using CPM.cmake, you can check this example. After adding CPM script to your project, implement the following snippet to your CMake:

CPMAddPackage(
    NAME nlohmann_json
    GITHUB_REPOSITORY nlohmann/json
    VERSION 3.9.1)
Last update: November 1, 2023