Avisynth is a scripting language and a collection of filters for non-linear video editing tasks.

AviSynth itself does not provide a graphical user interface (GUI) but instead relies on a script system that allows advanced non-linear editing.

While this may at first seem tedious and unintuitive, it is remarkably powerful and is an excellent way to manage projects in a precise, consistent, and reproducible manner. Because text-based scripts are human readable, projects are inherently self-documenting.

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.