Manatee

How to convert AIFF to MP3 on a Mac

· 5 min read

AIFF is Apple’s uncompressed audio format, the same quality as a CD and about 10 MB per minute of stereo. To turn it into MP3 on a Mac you can use the Music app that is already installed (set its import encoder to MP3, then choose File, Convert, Create MP3 Version), or drop the files on Manatee and pick MP3, which skips the library entirely. Either way, keep the AIFF if it is the only master you have.

What you are trading away

AIFF stores every sample exactly. MP3 throws away the parts of the sound that a model of human hearing says you will not miss, and in return the file shrinks by a factor of five to ten. At 320 kbps, the highest standard MP3 setting, a minute of audio is about 2.4 MB; at 128 kbps it is under 1 MB. For a song on a phone, a podcast, or a clip to email, the difference is inaudible to nearly everyone on nearly every speaker. For a recording you might edit, remix, or master later, it is not a conversion you can undo: an MP3 turned back into AIFF is a bigger file with the same missing detail.

So the rule is simple. Convert a copy for sharing and keep the AIFF for archiving. Lossless vs lossy goes into what actually gets discarded, if you are curious.

Convert with the Music app

Every Mac ships with the Music app, and it still contains the converter that used to live in iTunes. It is a perfectly good MP3 encoder; the catch is that it only converts things in your library, and it leaves both versions there afterward.

  1. Open Music and choose Music, Settings (Preferences on older macOS), then the Files tab.
  2. Click Import Settings. Set Import Using to MP3 Encoder and Setting to Higher Quality (192 kbps), or choose Custom to pick up to 320 kbps. Click OK twice.
  3. Add the AIFF to your library: File, Import, or drag the file into the Music window. If “Copy files to Music Media folder when adding to library” is on in the Files tab, Music duplicates the file into its own folder; that is fine.
  4. Select the track. Choose File, Convert, Create MP3 Version. A second track with the same name appears a few seconds later.
  5. Right-click the new track and choose Show in Finder to get the MP3 file itself. Drag it wherever you need it.
  6. Go back to Import Settings and restore your previous encoder, otherwise every CD or file you add to Music from now on will be imported as MP3.

For a folder of AIFFs, select them all in step 4; Music converts them one after another.

Convert with Manatee

Manatee is a converter rather than a library, so there is nothing to import and nothing left behind except the new file.

  1. Open Manatee. Every feature is free for 24 hours with no account; after that it is $9 once.
  2. Drag one AIFF, or a folder of them, onto the menu bar icon or into the window’s drop zone.
  3. Choose Convert and pick MP3.
  4. Each job writes an MP3 beside its source. The AIFF is never modified.

Manatee accepts .aif and .aiff (the two spellings are identical formats), along with WAV, FLAC, M4A, and most other audio you are likely to have. It also offers M4A, WAV, and FLAC as targets, which matters in the section after next.

What it does not do: it is not an audio editor. It will not normalize loudness, trim silence, split a long recording into tracks, or edit tags. If you need any of that, do it before or after the conversion in an editor.

Pick the right bitrate

If you are using the Music app you choose the bitrate in Import Settings, and the choice is less agonizing than it looks.

  • 128 kbps: voice recordings, lecture audio, anything going over a slow connection. Noticeably flat on music if you listen closely.
  • 192 kbps: the sensible default for music that will be played casually.
  • 256 to 320 kbps: music you care about, on headphones. Diminishing returns above this; the format simply cannot carry more.

Variable bitrate (VBR), where available, spends bits where the music is complex and saves them where it is quiet, and usually gives a better result than the same average at a constant rate.

When MP3 is the wrong target

MP3 is the universal choice, but it is not the best choice in every situation, and both tools above can write the alternatives.

  • If the listener is on an iPhone, Mac, or anything made in the last decade, M4A (AAC) sounds better than MP3 at the same size. The Music app offers an AAC Encoder in the same Import Settings menu, and Manatee has M4A as a target. The procedure is the same as for MP3; see how to convert M4A to MP3 on a Mac for the reverse direction.
  • If you need the file smaller but cannot afford to lose anything, FLAC compresses losslessly to roughly half the size of AIFF. Manatee converts to FLAC directly; the Music app does not.
  • If a piece of software insists on WAV, that is the same uncompressed audio as AIFF in a different wrapper, and the conversion is instant and lossless. How to convert WAV to MP3 on a Mac covers the WAV side of the same job.

Questions

What is the difference between .aif and .aiff?

Nothing. They are the same format; .aif is the three-letter spelling from the days when file systems required one. Either converter treats them identically.

Does converting delete the original AIFF?

Not with either method here. Music adds a second track and keeps the first; Manatee writes a new file alongside and never touches the source. Delete the AIFF yourself if you decide you do not need it, and think twice before you do.

The MP3 sounds the same as the AIFF. Did it work?

Yes. That is the point of a good lossy encoder: the file is a fraction of the size and the difference is below what you can hear on ordinary equipment. Compare file sizes in Finder’s Get Info if you want proof.

Can I turn the MP3 back into AIFF later?

You can convert it, and some programs require AIFF input, but the detail the MP3 encoder discarded does not come back. The result is a large file with MP3 quality inside it.