#define JSON_HAS_STD_FORMAT /* value */
This macro indicates whether the standard library has support for std::format/std::formatter (that is, the <format> header). Possible values are 1 when supported or 0 when unsupported.
The default value is detected based on the preprocessor macros #!cpp JSON_HAS_CPP_20 and #!cpp __cpp_lib_format.
When the macro is not defined, the library will define it to its default value.
!!! info “Enabled functionality”
When this macro evaluates to `1`, the library provides a [`std::formatter<basic_json>`](../basic_json/std_formatter.md) specialization so JSON values can be used directly with `std::format`.
??? example
The code below forces the library to disable support for `std::format`, even if the standard library would otherwise support it: ```cpp #define JSON_HAS_STD_FORMAT 0 #include <nlohmann/json.hpp> ... ```