MP4 to MP3 Converter
Pull the audio track out of a video as an MP3.
File
Result
Your converted file will appear here.
About the MP4 to MP3 converter
A recorded talk, an interview, a screen capture with commentary — often the video is only a carrier and what you actually want is the sound. This converter decodes the audio track and writes it out as an MP3.
The video stream is discarded entirely rather than being processed, which is why a large file converts far faster than a full transcode would.
Which video files work
Anything your browser can play: MP4 and MOV with AAC audio, WebM with Opus or Vorbis, and usually MKV. If the file plays in a browser tab, its audio can be extracted here.
A video with no audio track will report that it contains no audio rather than producing a silent file.
Choosing a bitrate
192 kbps is the sensible default for music — most listeners cannot reliably tell it from the source on ordinary equipment. 320 kbps is the ceiling MP3 allows and worth it if the file is going to be archived or edited further.
For speech — interviews, lectures, podcasts, voice notes — 96 kbps mono is plenty and produces a file several times smaller. Music at that rate starts to sound obviously thin, particularly in cymbals and reverb tails.
How the conversion works
Your browser decodes the file with the Web Audio API — the same decoder it uses to play media — which hands back raw PCM samples. Those samples are then re-encoded into the output format.
MP3 encoding uses LAME compiled to JavaScript, running in a background worker so a long file does not freeze the page. Nothing is uploaded: no server sees the audio, there is no queue, and there is no processing limit beyond your own device.
Frequently asked questions
Does the video need to finish uploading first?
There is no upload. The file is read straight off your disk, so conversion starts immediately regardless of how large it is.
Why is my two-hour recording slow?
Decoding and re-encoding two hours of audio is real work, and it is your device doing it. It runs in a background worker so the page stays responsive, but it is not instant. Mono at 96 kbps is considerably quicker.
Will converting reduce the quality?
Re-encoding lossy audio always loses a little, because the encoder is working from what survived the first compression rather than from the original. Keep the bitrate at or above the source and it will not be audible. Converting from a lossless source such as WAV or FLAC has no such problem.
Is my file uploaded?
No. Decoding and encoding both happen in your browser. The audio never leaves your device, which is why there is no size limit imposed by a server.