ARDUINOJSON_USE_LONG_LONG determines the type used to store integer values in JsonVariant.

  • If ARDUINOJSON_USE_LONG_LONG == 0, then JsonVariant stores a long
  • If ARDUINOJSON_USE_LONG_LONG == 1, then JsonVariant stores a long long

The default is 0 when ARDUINO is defined, 1 otherwise. In other words, it’s long on embedded systems, but long long on computers.

To override the default value, you need to #define the value before including ArduinoJson.h, like this:

#define ARDUINOJSON_USE_LONG_LONG 1
#include <ArduinoJson.h>

Breaks the ArduinoJson Assistant

The ArduinoJson Assistant assumes that you use the default settings.

If you change this value, the capacity required to store your document will change, and the results given by the ArduinoJson Assistant won’t match.

Several .ino or .cpp files?

Be careful if several compilation units compose your program, i.e., if your project contains several .ino or .cpp files.

You should define the same value of ARDUINOJSON_USE_LONG_LONG in each compilation unit; otherwise, the executable will be much bigger because it will contain two variants of the library.