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- toc
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# JSON for Modern C++
![JSON for Modern C++](images/json.gif)
JSON for Modern C++ is a header-only C++11 library that turns JSON into a first-class C++ data type, using the operator
magic of modern C++ so that creating, reading, and modifying JSON values feels as natural as it does in languages like
Python. The whole library is available as a single header, `json.hpp`, with no dependencies, no subproject, and no
complex build system to set up; a companion header, `json_fwd.hpp`, provides forward declarations to keep compile times
down, `<nlohmann/json_literals.hpp>` holds the user-defined string literals on their own, and
`<nlohmann/json_view.hpp>` adds zero-copy views and editable documents. See
[header-only integration](integration/index.md) for details. It is heavily unit-tested with 100% code
coverage, checked with Valgrind and the Clang Sanitizers for memory leaks, and continuously fuzz-tested by Google
OSS-Fuzz.
## Quick start
Add the single header to your project and use the library like this:
```cpp
#include <iostream>
#include <nlohmann/json.hpp>
using nlohmann::json;
int main()
{
// parse a JSON string
json j = json::parse(R"({"happy": true, "pi": 3.141})");
// access and modify values
j["name"] = "Niels";
j["list"] = {1, 0, 2};
// read a value into a C++ variable and use it
double pi = j["pi"].get<double>();
std::cout << "2 * pi = " << 2 * pi << '\n';
// serialize with an indent of 4 spaces
std::cout << j.dump(4) << '\n';
}
```
Get the library by copying the single header [`json.hpp`](https://github.com/nlohmann/json/releases) from the
releases page into a directory `nlohmann` on your include path, or by installing it with a package manager:
```sh
brew install nlohmann-json # Homebrew
vcpkg install nlohmann-json # vcpkg
```
```cmake
find_package(nlohmann_json 3.12.0 REQUIRED)
target_link_libraries(myproject PRIVATE nlohmann_json::nlohmann_json)
```
See [Integration](integration/index.md) for CMake in detail, all supported package managers (Conan, Meson, Bazel,
Conda, and more), and pkg-config.
## Explore the documentation
<div class="grid cards" markdown>
- :octicons-rocket-24:{ .lg .middle } __Features__
---
Creating, parsing, accessing, and serializing JSON values, JSON Pointer/Patch, binary formats, zero-copy views,
and more.
Creating, parsing, accessing, and serializing JSON values, converting your own C++ types, JSON Pointer/Patch/Merge
Patch, binary formats, zero-copy views, and more.
[:octicons-arrow-right-24: Features](features/index.md)
@@ -112,11 +60,5 @@ Conda, and more), and pkg-config.
</div>
!!! info "Unreleased changes"
This documentation is built from the `develop` branch and may describe changes that are not part of a release
yet. Their version numbers are followed by an <span class="unreleased-version">unreleased</span> badge; see
[Releases](home/releases/index.md) for what shipped in each version.
The library is licensed under the [MIT License](home/license.md). The source code, issue tracker, and discussions
are on [GitHub](https://github.com/nlohmann/json).
![JSON for Modern C++](images/json-light.svg#only-light)
![JSON for Modern C++](images/json-dark.svg#only-dark)