ArduinoJson
JSON library for Arduino and embedded C++. Simple and efficient
...::istream. ArduinoJson can produce compact or prettified documents. ArduinoJson works directly with strings stored in program memory. ArduinoJson supports two coding styles, with implicit or explicit casts. ArduinoJson deduplicates strings in the JSON document. When you have several identical keys or values, the JsonDocument only stores one of each. In practice, this feature reduces memory consumption by 20-30%.