AviSynth is a powerful tool for video post-production. It provides ways of editing and processing videos. It works as a frameserver, providing instant editing without the need of temporary files.

AviSynth itself doesn’t provide a graphical user interface (GUI). Instead of that it relies on a script based system that allows advanced non-linear editing. The scripting language is simple yet powerful, and complex filters can be created from basic operations to develop a sophisticated palette of useful and unique effects.

AviSynth works by faking .AVI files. That means that AviSynth scripts work in principle with all media applications and players capable of opening .AVI files.