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MP4 to MP3 pulls the audio out of a video: a recorded lecture you want to listen to on a run, a concert clip, an interview to transcribe. The video stream is discarded and the audio is encoded to MP3 at your chosen bitrate — 192 kbps is transparent for most content. Powered by FFmpeg compiled to WebAssembly, running entirely on your device.
Frequently asked questions
Why did I get a "no audio track" error?
Some videos genuinely have no sound — screen recordings without a mic and some downloaded clips. The error means the MP4 contained nothing to extract, not that conversion failed.
What bitrate should I choose?
192 kbps for speech and general listening (transparent, compact); 320 kbps for music you care about. For voice memos, even 128 kbps is clean.