Hi Peter, thank you for reporting this and also sorry for difficulties. They made some major changes between version 5 and 6 of ArduinoJson library. I upgraded the Arduino sketch - see attached one. It can be compiled now however I don't have any ESP8266 around so didn't make any further tests. Let me know about your progress. Regards, Tomas 0_1554469564091_REXYGEN_REST_API_example.ino