If you’ve ever tried encoding GIFs with ffmpeg there’s a good chance your results came out looking pretty bad. This is because GIFs are limited to a palette of 256 colours and ffmpeg just uses a generic palette to be able to cover a wide range of colours.

gifgen produces much better results by doing a 2-pass encode. The first pass generates a custom colour palette based on all of the pixels from each frame. The second pass encodes the GIF using this palette instead of the default one bundled with ffmpeg.