Trimming audio in MacOS

A how-to guide for trimming MP3 audio in macOS Sierra using just the software that comes with your Mac.

We make a lot of videos here at Biteable, and it probably goes without saying that we use our own software to do it. We have a good selection of audio tracks for use in the app already, but when we have a particular feel in mind we often reach for a custom audio track. Our article How to Find Royalty Free Music for Your Video is good place to start when searching for royalty-free music you can use. But finding the right audio track is only half the battle. Here is our process for trimming an audio track to the right length.

I’ve got my audio, but I want to trim it…

Open that bad boy up in QuickTime. Depending on your setup, audio files probably open in iTunes or some other app, so right-click and choose Quicktime from the Open With menu option.

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Enter Trim Mode

From the Edit menu in the toolbar, choose Trim…

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Adjust start and end positions

Trim mode shows a nice visualisation of the volume throughout the clip. This audio track (used on this video if you’d like to hear it) actually came with both a short and long version of the track in the same audio file. You can clearly see a quiet spot at about the 1 min mark between the short version ends and the long version starting. I just want the long version.

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I’m going to grab the left-hand-side “handle” and drag it to meet the start of the part of the audio I want.

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You can drag the window as wide as you like so that you can see the audio track in more detail.

Pro tip: The Play, Fast-Forward, and Rewind buttons will only work on the trimmed part of the audio (the bit within the yellow range). By adjusting your trim handles then clicking Rewind and Play you can ensure you line up the audio just right.

Once you’re happy, click the Trim button.

Save as audio

Quicktime is really an application for playing video, so when we clicked Trim it’s made an empty video with an audio track for us. Not to worry, we only want the audio anyway so lets choose Export then Audio Only… from the File menu.

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I’m saving my audio file to the Desktop and naming it “audio_track__trimmed”. But you can name it whatever and put wherever you want, I’m not your boss.

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You might have noticed that QuickTime saved the file with a “.m4a” file extension? We’re about to fix that.

Rename to MP3 format

Technically speaking an MP3 and an M4A file store the audio in slightly different ways. However, Biteable’s got your back and will happily play an M4A that we sneakily disguise as an MP3.

Find your exported trimmed audio file, then Right click and choose Get Info.

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In the Name and Extension section, change the file extension to “mp3” — literally just type in mp3 in the place of m4a and hit enter. MacOS will get all up your face with an “Are you sure…” message.

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Yes, we do want to Use .mp3.

You’re done with your info window so you can close that. And… you’re finished! Upload your trimmed track to your Biteable video and get it out there!


Just as there are different ways to skin cats (or so they say, it sounds horrible if you ask me), this is not the only way to trim audio on a Mac. QuickTime isn’t the perfect solution either, but it comes installed and ready to use on just about every Mac ever made, saving you the hassle of having to find and download special software.