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static basic_json meta();

This function returns a JSON object with information about the library, including the version number and information on the platform and compiler.

Return value

JSON object holding version information

key description
compiler Information on the used compiler. It is an object with the following keys: c++ (the used C++ standard), family (the compiler family; possible values are clang, icc, gcc, ilecpp, msvc, pgcpp, sunpro, and unknown), and version (the compiler version).
copyright The copyright line for the library as string.
name The name of the library as string.
platform The used platform as string. Possible values are win32, linux, apple, unix, and unknown.
url The URL of the project as string.
version The version of the library. It is an object with the following keys: major, minor, and patch as defined by Semantic Versioning, and string (the version string).

Exception safety

Strong guarantee: if an exception is thrown, there are no changes to any JSON value.




The following code shows an example output of the meta() function.

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

using json = nlohmann::json;

int main()
    // call meta()
    std::cout << std::setw(4) << json::meta() << '\n';


    "compiler": {
        "c++": "201103",
        "family": "clang",
        "version": "12.0.0 (clang-1200.0.22.19)"
    "copyright": "(C) 2013-2020 Niels Lohmann",
    "name": "JSON for Modern C++",
    "platform": "apple",
    "url": "",
    "version": {
        "major": 3,
        "minor": 9,
        "patch": 1,
        "string": "3.9.1"

Version history

  • Added in version 2.1.0.