Files with the AVS extension are associated with an advanced tool used in film post-production called AviSynth. AVS files are used by the program to store scripts responsible for the appropriate processing of video material in a non-linear manner. Technically, these are plain text files and can be opened with any editor. The scripting language used in AVS files is simple in syntax, and at the same time offers great possibilities.

AviSynth is a tool that works as a frameserver. It processes the files on the fly and the data is passed to the target program.