Current version is 6.12.0.
If you're upgrading from version 5 <ArduinoJson5>, some changes will be required to your code. See the Version 6 Migration Guide for details.
Some methods of JsonVariant have been removed, replacements are:
asString() -> as<char*>() or as<const char*>. Note that as<String> produces a serialized version, so you’ll get “null” instead of an empty/invalid result String.
asArray() -> as<JsonArray>()
asObject() -> as<JsonObject>()
There are also some useful helper functions available in the Json namespace. See Libraries/ArduinoJson6/include/ArduinoJson.h.
:cppJsonObjectStream