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
Codegen for all basic features	Yes	Yes	Yes	Yes	Yes	WIP
JSON parsing	Yes	No	No	No	No	No
Simple mutation	Yes	WIP	WIP	No	No	No
Reflection	Yes	No	No	No	No	No
Buffer verifier	Yes	No	No	No	No	No
Testing: basic	Yes	Yes	Yes	Yes	Yes	WIP
Testing: fuzz	Yes	No	No	Yes	Yes	No
Performance:	Superb	Great	Great	Great	Ok	?
Platform: Windows	VS2010	Yes	Yes	?	?	?
Platform: Linux	GCC282	Yes	?	Yes	Yes	?
Platform: OS X	Xcode4	?	?	?	Yes	?
Platform: Android	NDK10d	Yes	?	?	?	?
Platform: iOS	?	?	?	?	?	?
Engine: Unity	?	?	Yes	?	?	?
Primary authors (github)	wvo	wvo	(ev/js)	rw	rw	(ev)