I get to be one of the lucky few to learn today that ffmpeg was ported (well, transpiled) to WASM. This is more specifically built on that port: https://github.com/ffmpegwasm/ffmpeg.wasm
This also means that despite being a locally hosted ffmpeg frontend, it's still slower than native ffmpeg and bound to WASM limits like file size (still a generous 2GB for images and audio, but not as viable for big video conversions).
Still weird that this project doesn't seem to acknowledge that anywhere.
they may have updated the website since the numerous comments here but the about section acknowledges all the libraries they use
Libraries
A big thanks to FFmpeg (audio, video), libvips (images) and Pandoc (documents) for maintaining such excellent libraries for so many years. VERT relies on them to provide you with your conversions.
That project has an interactive playground that essentially describes and demonstrates how it works: https://ffmpegwasm.netlify.app/playground
This also means that despite being a locally hosted ffmpeg frontend, it's still slower than native ffmpeg and bound to WASM limits like file size (still a generous 2GB for images and audio, but not as viable for big video conversions).
Still weird that this project doesn't seem to acknowledge that anywhere.