Audio format comparison
MP3 vs m4a
MP3 plays on every device made in the last 25 years. m4a plays on every device made in the last 15 years. m4a is more efficient — 128 kbps AAC sounds like 192 kbps MP3, files are smaller. For YouTube audio downloads specifically, m4a is a direct copy of the YouTube source; MP3 requires re-encoding which adds another lossy compression pass. Pick MP3 only when you need universal compatibility (old car stereos, vintage MP3 players).
Side-by-side
| Feature | MP3 | m4a | Winner |
|---|---|---|---|
| YouTube source | Requires transcode (quality loss) | Direct copy (lossless) | m4a |
| File size at equivalent quality | Baseline | ~30% smaller | m4a |
| Compatibility | Universal (every device since 2005) | Universal modern (every device since 2010) | MP3 |
| Encoding age | 1993 (old) | 2003 (newer) | m4a |
| Default for music platforms | Old downloads only | Apple Music, YouTube, Spotify backend | m4a |
| Car stereo support | Universal | Universal in cars from 2010+ | MP3 |
MP3 wins on
- Universal compatibility — works on absolutely every device made since 2005.
- Decade-mature ecosystem — every audio tool handles it.
- No DRM concerns or licensing issues for end users.
- Predictable file sizes given a target bitrate.
m4a wins on
- ~30% smaller file at the same audio quality.
- YouTube's source format — direct copy with zero quality loss.
- Better at low bitrates (96 kbps AAC sounds like 128 kbps MP3).
- Native Apple ecosystem format.
Verdict
For YouTube downloads: m4a is the right answer. It's a byte-for-byte copy of the audio YouTube stored, no quality loss, smaller file size. Choose MP3 only when your destination device is too old for m4a (which is increasingly rare — most consumer hardware made since 2010 plays m4a fine).