MP4 to MP3

Why convert MP4 to MP3

Keep just the sound of a video: a lecture, an interview, a song from a recording you made, or a podcast that was filmed. MP3 files are a fraction of the video's size and play on anything, including car stereos and old MP3 players.

MP4 is MP4, the everyday video format of phones, cameras and downloads; MP3 is MP3, the audio format every player, car stereo and phone plays.

What changes

• Only the sound is kept; the picture is dropped, which is why the file gets so much smaller.
• The sound is decoded and encoded again as MP3. At 192 kbps or more you won't hear a difference from the MP4.
• Sample rate and channels are kept (mono stays mono, stereo stays stereo).

On your device

Your files are converted by your browser and never uploaded, so there is no sign-up, no file-size cap beyond your free disk space and no daily limit. You can convert up to five files at once.

The file is read in slices by Mediabunny in a Web Worker, which finds the audio track; your browser's built-in decoders (WebCodecs) turn it into sound samples, which are then encoded as MP3 by LAME, the open-source MP3 encoder, compiled to WebAssembly and loaded only when needed, at the bitrate you choose. The result is written to the browser's private storage as it is produced, so long recordings don't need to fit in memory, then offered for download. Nothing is uploaded.