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api/macros/json_has_std_format.md

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+# JSON_HAS_STD_FORMAT
+
+```cpp
+#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.
+
+## Default definition
+
+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.
+
+## Notes
+
+!!! 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`.
+
+## Examples
+
+??? 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>
+
+    ...
+    ```
+
+## Version history
+
+- Added in version 3.12.x.