MP4 to MP3 converter

What happens to the sound

The audio in an MP4 is almost always AAC, already compressed. Making an MP3 means decoding it and compressing it again in a different format, which loses a little each time, so the MP3 can never be better than the soundtrack it came from. At 192 kbps and above, the second step is very hard to hear for music, and speech is safe at much lower rates.

If you only need the sound as a file, choose Original. It copies the audio stream out of the video exactly as it is, with no loss at all, and finishes almost instantly. AAC audio arrives as an M4A file, which phones, music apps and most players open; Opus or Vorbis audio from a WebM arrives as OGG.

Bitrate and file size

The MP3 encoder works at a constant bitrate, so the size depends only on the length and the bitrate you choose, not on the content. We measured it on a 40 second recording:

An hour long lecture at 128 kbps is about 55 MB. For recordings of a single voice, switch Channels to Mono: the size stays the same at a given bitrate, but the one channel gets all of the data, so a low bitrate such as 96 kbps goes further.

MP3, M4A or WAV

• MP3 plays on every device ever made, including car stereos and old players. Choose it when you do not know where the file will be played.
• M4A holds AAC audio, which sounds a little better than MP3 at the same bitrate and plays on every current phone and computer. Our encoder made it in half the time.
• WAV is uncompressed: about 10 MB per minute of stereo. Use it only to edit the sound in an audio program, then export from there.

Only part of the video

Fill in a start and an end, in seconds or as minutes and seconds such as 1:30, to keep just that part, for a ringtone or one song from a concert. The same times apply to every file in the list. For a precise cut with a waveform to see where the sound starts, convert the whole track first and use the audio cutter.

Speed

Encoding is fast: our 40 second recording took under a second as MP3 and about 0.4 seconds as M4A, roughly 50 to 100 times faster than real time.

If something goes wrong

• It says there is no audio. Some videos, such as many screen recordings and GIF style clips, have no sound track at all.
• The original audio cannot be stored in that container. Pick MP3, M4A or WAV instead of Original.
• The MP3 sounds worse than the video. Raise the bitrate to 256 or 320 kbps, or use Original to keep the sound untouched.
• The browser says it cannot do this. The tool needs WebCodecs, which Chrome, Edge, Safari 16.4 or newer and Firefox 130 or newer provide.

How we tested. A 39.6 second WAV recording of music and the same length of speech, encoded with the audio engine of this tool (mediabunny with its MP3 and AAC encoders) in Chrome at each bitrate. Sizes per minute are the file size divided by the length.