ArduinoJson comes with the four following macros:

#define ARDUINOJSON_VERSION "7.0.3"
#define ARDUINOJSON_VERSION_MAJOR 7
#define ARDUINOJSON_VERSION_MINOR 0
#define ARDUINOJSON_VERSION_REVISION 3

Here is how you can print ArduinoJson’s version:

Serial.print("Using ArduinoJson version ");
Serial.println(ARDUINOJSON_VERSION);  // 7.0.3

Here is how you can test that the expected version is installed:

#if ARDUINOJSON_VERSION_MAJOR!=7 || ARDUINOJSON_VERSION_MINOR<0
#error ArduinoJson 7.0+ is required
#endif

See also: