Are different flatbuffers versions compatible?

[kozakusek]

There is a lot of talking of how the schemas can nicely evolve.
But do we have some test or heavily enforced prinicple that the serialized format of a flatbuffer can be read by all versions (or at least is backward compatible)?

This might be especially important for situations when someone saves the messages on disk or connects services which might happen to rely on different (potentially very old) flatbuffer versions.