If you have an iPhone voice memo, a song bought from iTunes, or audio exported on a Mac, you have an M4A file. M4A and MP3 both hold compressed audio and both are everywhere, so it's fair to ask whether the difference matters. Mostly it comes down to one trade: M4A is a little more efficient, and MP3 plays on a little more.

#What M4A actually is

M4A is an MP4 file with no video - the same container your videos use, holding just a soundtrack. The ".m4a" extension simply tells apps there's no picture. Inside, the sound is usually AAC, a lossy format designed as MP3's successor, and occasionally ALAC (Apple Lossless), which keeps a perfect, CD-quality copy. The file extension doesn't tell you which; a music app or VLC's codec information will.

A few relatives share the family name: M4B is an audiobook with chapters and bookmarks, M4R is an iPhone ringtone, and M4P is an old copy-protected iTunes purchase.

#Where M4A files come from

  • iPhone Voice Memos save recordings as M4A.
  • iTunes Store purchases are AAC at 256 kbps in M4A files, and have been free of copy protection since 2009.
  • CDs imported into Apple Music or iTunes become M4A by default, as AAC or ALAC depending on the import setting.
  • QuickTime Player's Export As → Audio Only on a Mac writes M4A.
Head to head

M4A and MP3 compared

M4A MP4 audio, usually AAC
  • Slightly better sound for the same file size
  • Can also be lossless (ALAC)
  • Plays on Apple devices, Android, Windows 10 and 11, browsers
  • Some car stereos and older players can't
vs
MP3 the universal audio file
  • Needs a little more data for the same quality
  • Always lossy
  • Plays on literally everything
  • The safe choice for unknown devices
At 192 kbps and above, both sound the same as the original to nearly everyone. The real difference is where they play.

#Which sounds better?

At the same bitrate, AAC generally sounds as good as or better than MP3, and the gap is clearest at low bitrates, below about 128 kbps - which is why streaming services and phones favour it. At typical music bitrates of 192-256 kbps, both are indistinguishable from the original for nearly everyone. ALAC M4A is a different case: it's lossless, so it's a perfect copy and sounds better than any MP3, at about half the size of the original CD audio.

#Which plays on more devices?

MP3 wins. Every phone, computer, browser, smart speaker, car stereo and MP3 player made in the last twenty-five years plays it. M4A plays on all Apple devices, Android phones, Windows 10 and 11 and modern browsers, but some car stereos, older music players and a few web upload forms don't accept it.

#When to convert M4A to MP3

  • A car stereo, older music player or upload form refuses the M4A.
  • You're sending audio to people and don't know what they'll play it on.
  • You want one consistent format across a whole collection.

Wave's M4A to MP3 converts it in your browser without uploading it, as a 192 kbps MP3. Converting AAC to MP3 is a second round of lossy compression, so use 192 kbps or higher and the difference stays inaudible. For Apple Lossless files, ALAC to MP3 is only a single lossy step.

#When not to convert

  • MP3 to M4A gains nothing: the detail MP3 discarded can't be recovered, and you add another round of compression. Only do it if an app specifically requires M4A.
  • Apple Music downloads are copy-protected and only play inside Apple Music, so no converter can turn them into MP3s. The same goes for old .m4p iTunes purchases.

#The short version

  • M4A is MP4 with no video, usually holding AAC (lossy) and sometimes ALAC (lossless).
  • AAC is a little more efficient than MP3, but at 192 kbps and above both sound like the original.
  • MP3 plays on more devices. Convert M4A to MP3 when something refuses it.
  • Don't convert MP3 to M4A expecting better sound, and copy-protected Apple Music downloads can't be converted.