A new browser-based video compressor allows users to optimise footage directly on their device using FFmpeg compiled to WebAssembly. The tool accepts an uploaded file and generates multiple encoded versions with varying quality settings and output sizes. Users can then compare these files and download the smallest version that meets their specific requirements. All processing occurs locally without uploading data to external servers.
Simon Willison built the application after needing to publish an optimised version of an Equal Earth animation on his blog. He asked Claude Fable 5.1 to construct the tool via Claude Code using the WebAssembly build of FFmpeg. This approach removes the need for large cloud uploads and gives developers precise control over encoding parameters without leaving their machine.
* Built using FFmpeg compiled to WebAssembly
* Processes files entirely locally within the browser
* Generates multiple encoded versions for comparison
