MP4 to MP3 on a Mac

macOS can extract audio in three different places, and each one hands you something slightly different. Here is which to use when.

macOS can extract audio in three different places, and each hands you something slightly different. Two of them will not give you an MP3 at all, which is usually what sends people looking.

QuickTime Player: audio only, but not MP3

QuickTime has had this since forever, and it is one menu deep: open the video, then File → Export As → Audio Only. What lands on your disk is an .m4a.

That is not a failure — for a video filmed on an iPhone, an .m4a is the best possible result, because the soundtrack is already AAC and this keeps it. It is only a problem when something downstream specifically wants MP3, and no amount of clicking in QuickTime will produce one.

One quirk: on some macOS versions the export is a re-encode rather than a copy, which you can spot because a long film takes minutes rather than seconds. Extracting here is always a copy when the source is AAC, and says so before it runs.

The Music app: MP3, but only for audio you already have

Music can convert files — Settings → Files → Import Settings, choose MP3 Encoder, then select a track and use File → Convert → Create MP3 Version. The catch is that Music will not import a video file to begin with, so this route only works once the audio is out of the video by some other means. As a second step after QuickTime's M4A, it works fine.

If "Create MP3 Version" is greyed out, the usual causes are that the selected item is not a local file, that it is a purchased or Apple Music track with protection on it, or that the import setting is still on AAC.

Terminal: the one-liner

macOS ships afconvert, which converts audio but does not read video containers. For video, install FFmpeg (brew install ffmpeg) and then:

ffmpeg -i video.mp4 -vn -c:a libmp3lame -b:a 192k audio.mp3

Or, to take the soundtrack out with nothing re-encoded at all — seconds even on a two-hour film:

ffmpeg -i video.mp4 -vn -c:a copy audio.m4a

For a whole folder, in zsh:

for f in *.mp4; do ffmpeg -i "$f" -vn -c:a libmp3lame -b:a 192k "${f%.mp4}.mp3"; done

More FFmpeg recipes, including choosing between several soundtracks.

The browser: MP3 without installing anything

Drop the file on this page in Safari, Chrome or Firefox. It gives you MP3, M4A, WAV, FLAC and more, tells you which of them is a copy rather than a conversion, and never uploads the video — the work happens in the tab, which you can prove by pulling the Wi-Fi after the page loads.

It is also the only one of these routes that lets you pick between several soundtracks, which matters the moment you are dealing with an MKV rather than an MP4.

Choosing between them

One macOS-specific trap

If the video lives in iCloud Photos or iCloud Drive with "Optimise Mac Storage" on, the file on disk may be a placeholder. Every tool here will then fail in a different confusing way — QuickTime will not export, FFmpeg reports invalid data, the browser says the file cannot be read. Open the video and let it download fully first, and all three start working.

If the video is on your phone anyway

AirDropping a 2 GB recording to the Mac to extract 5 MB of audio is a lot of waiting for nothing. The iPhone app converts it on the phone in two taps, and you AirDrop the finished audio instead — or skip the Mac entirely.