[samsartor]

https://ruffle.rs/ is pretty solid

[adrian17]

I'm talking about the .fla (XFL) format, not .swf (which is documented well - though that doesn't mean its exact behavior its understood well)

(note: I'm one of Ruffle's maintainers)

[Cr8]

ruffle is a player for the output format (swf), .fla is the authoring format