About MP4 and WAV
MP4 is the standard video container on the web. Extracting its audio track is a quick way to turn a music video, lecture, or recording into a listenable file.
WAV is uncompressed PCM audio — the raw samples with a small header. It's the standard interchange format for recording, sampling, and production work, at the cost of roughly 10 MB per minute of stereo.
Extracting audio from MP4 re-encodes only the audio track — the video is discarded, so even long files finish quickly.
How the conversion works
This tool runs FFmpeg — the same engine behind most media software — compiled to WebAssembly, entirely in your browser. Your file is read locally, converted locally, and saved straight from memory; nothing is ever uploaded, which also means no queues and no server-side file size limits.
The converter itself is a one-time ~31 MB download on your first conversion, cached by the browser afterwards. Once it's loaded, everything works offline.