Detaching audio in iMovie, and exporting audio only
iMovie on the Mac can export audio on its own. iMovie on the iPhone cannot, and that difference is why this search exists.
Free on iPhone and iPad, for the videos already in your camera roll. Works offline; one free conversion, then a subscription.
iMovie can separate audio from video in one click. Whether it can then hand you that audio as a file depends entirely on which iMovie you are using — and the difference between the Mac and the iPhone version is why this is such a common dead end.
On a Mac: detach, then export audio only
- Drag the video into a project and onto the timeline.
- Select the clip and choose Modify → Detach Audio (or ⌥⌘B). The soundtrack appears as a separate green bar beneath the video.
- To get it out on its own: File → Share → File…, and in the Format menu choose Audio Only.
- Pick a file format — AAC, MP3, AIFF or WAV — and export.
That is a real audio-only export and it works well. The one thing to know is that it re-encodes: iMovie renders the timeline, so the audio you get has been decoded and compressed again, at whatever quality the format menu implies. For an edit that is expected; for a straight extraction it is a generation you did not need to lose.
On an iPhone or iPad: detach yes, export no
iMovie on iOS has Detach: tap the clip on the timeline, then the scissors icon, then Detach. The audio separates exactly as it does on the Mac.
Then you hit the wall. Every share option in iOS iMovie produces a video. There is no Audio Only format, there never has been, and no amount of deleting the video track changes it — you get a black video with sound, not an audio file.
So on an iPhone the honest options are: export the black video and extract audio from it afterwards (wasteful but it works), or skip iMovie entirely and take the audio straight out of the original video. Four ways to do that on an iPhone.
Why "delete the video and export" is a bad habit
It survives as advice because it technically produces something. What it actually does is render a full video file — black frames encoded at your export resolution, which can be hundreds of megabytes — wrapped around audio that has been re-encoded on the way. Then you still have to extract the audio from it.
Compare that with opening the original video in the extractor here: the soundtrack is lifted out of the container without being decoded, in seconds, at exactly the quality it was recorded. No render, no black frames, no second encode.
Which format to pick in iMovie's export
| Format | Use it for | Note |
|---|---|---|
| AAC | Anything modern | Lands as .m4a; the best quality-per-megabyte of the four |
| MP3 | Old hardware, upload forms | A second lossy encode, like all MP3 from video |
| WAV | Another editor, transcription | Uncompressed — about 10 MB per minute |
| AIFF | Logic and older Mac audio tools | Uncompressed, same size as WAV |
When iMovie is the right tool anyway
If you are actually editing — cutting between clips, adjusting levels, adding music — then detaching audio inside iMovie is exactly right, and exporting Audio Only at the end is the correct last step. The point of this page is narrower: if all you ever wanted was the sound from one video, the editor is a long way round.
Extracting audio does not need a timeline at all — the tool above does it in a browser tab.