FlatBuffers is actively being worked on, which means that certain platform / language / feature combinations may not be available yet.

This page tries to track those issues, to make informed decisions easier. In general:

Languages: language support beyond the ones created by the original FlatBuffer authors typically depends on community contributions.
Features: C++ was the first language supported, since our original target was high performance game development. It thus has the richest feature set, and is likely most robust. Other languages are catching up however.
Platforms: All language implementations are typically portable to most platforms, unless where noted otherwise.

NOTE: this table is a start, it needs to be extended.

Feature	C++	Java	C#	Go	Python	JS	TS	C	PHP	Dart	Lobster	Rust	Swift
Codegen for all basic features	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	WiP	Yes	Yes	Yes	Yes
JSON parsing	Yes	No	No	No	No	No	No	Yes	No	No	Yes	No	No
Simple mutation	Yes	Yes	Yes	Yes	No	No	No	No	No	No	No	No	Yes
Reflection	Yes	No	No	No	No	No	No	Basic	No	No	No	No	No
Buffer verifier	Yes	No	No	No	No	No	No	Yes	No	No	No	No	No
Native Object API	Yes	No	Yes	Yes	Yes	Yes	Yes	No	No	Yes	No	No	No
Optional Scalars	Yes	Yes	Yes	No	No	Yes	Yes	Yes	No	No	Yes	Yes	Yes
Flexbuffers	Yes	Yes	?	?	?	?	?	?	?	?	?	Yes	?
Testing: basic	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	?	Yes	Yes	Yes	Yes
Testing: fuzz	Yes	No	No	Yes	Yes	No	No	No	?	No	No	Yes	No
Performance:	Superb	Great	Great	Great	Ok	?	?	Superb	?	?	Great	Superb	Great
Platform: Windows	VS2010	Yes	Yes	?	?	?	Yes	VS2010	?	Yes	Yes	Yes	No
Platform: Linux	GCC282	Yes	?	Yes	Yes	?	Yes	Yes	?	Yes	Yes	Yes	Yes
Platform: OS X	Xcode4	?	?	?	Yes	?	Yes	Yes	?	Yes	Yes	Yes	Yes
Platform: Android	NDK10d	Yes	?	?	?	?	?	?	?	Flutter	Yes	?	No
Platform: iOS	?	?	?	?	?	?	?	?	?	Flutter	Yes	?	Yes
Engine: Unity	?	?	Yes	?	?	?	?	?	?	?	No	?	No
Primary authors (github)	aard	aard	ev/js/df	rw	rw	ew/ev	kr	mik	ch	df	aard	rw/cn	mi/mz