Gnash is a player for animated "movies" in the Macromedia Shockwave Flash
(.swf) format.  It can be run as a graphical application, as a Web browser
plugin, or as a library used by other programs.  It is not yet complete;
it does not correctly handle every .swf file.

Many of the Flash movies that I come across play fine in Gnash.  Many
others do not.  In particular, Flash movies that are used for browser
navigation may still have a few issues with some URLs left. Most
Flash based navigation of a web site should work.

Gnash supports the majority of Flash opcodes up to SWF version 7, and
a wide sampling of ActionScript classes for SWF version 7. All the core
ones are implemented, and many of the newer ones work, but may be missing
some of their methods. All unimplemented opcodes and ActionScript classes
and methods print a warning when using -v with gnash or gprocessor. Using
gprocessor -v is a quick way to see why a movie isn't playing correctly.