We built ConvertPrivately as an alternative to cloud-based conversion tools. It is an in-browser tool for converting audio and video files. It uses FFmpeg and your own CPU, meaning nothing gets sent to servers. It's free, has no ads, and doesn't touch your data. Plus, it's faster because it skips the upload/download step.

It's open source. You can see the code and improve it. You can even host the website yourself. No fluff, just conversion.

https://github.com/convertprivately/convertprivately/