M4A vs MP3
M4A (AAC) sounds better than MP3 at the same bitrate, which is why Apple and YouTube both use it. MP3 plays on absolutely everything, including hardware from twenty years ago. For quality pick M4A; for certainty pick MP3.
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Choose M4A when
- Apple devices, and anything modern.
- Lower bitrates, where AAC pulls clearly ahead of MP3.
Choose MP3 when
- Old car stereos, DJ equipment and cheap MP3 players.
- Anywhere you cannot check what the other end supports.
What M4A actually is
M4A is an MP4 container holding an AAC stream. AAC was designed as the successor to MP3 and it delivers clearly better sound at the same bitrate, particularly below 128 kbps. It is the default for Apple Music, YouTube audio and most streaming services.
M4A, M4B, M4R and AAC are largely the same thing with different extensions. Renaming usually works, though it is not something to rely on.
What MP3 actually is
MP3 discards the parts of a sound that psychoacoustic models say you are least likely to hear, then compresses the rest. It was the format that made digital music portable, and while newer codecs beat it at every bitrate, nothing matches its compatibility.
Converting an MP3 to another lossy format compounds the damage, because the second encoder is guessing at audio the first one already threw away.
M4A and MP3 side by side
| M4A | MP3 | |
|---|---|---|
| Extension | .m4a | .mp3 |
| Media type | audio/mp4 | audio/mpeg |
| Compression | Lossless | Lossless |
| Transparency | No | No |
| Animation | No | No |
| Quality setting | Not applicable | Not applicable |
| We can write it | Yes | Yes |
Questions
Is M4A the same as AAC?
Near enough. M4A is the container; AAC is nearly always the audio inside it. An M4A can also hold ALAC, which is lossless and much larger.
Why does my voice memo come out as M4A?
Because iOS records AAC in an M4A container. Converting to MP3 is the usual fix for software that will not open it.