Quick verdict
AAC if you control playback (your iPhone library, your podcast, your video soundtrack). MP3 if you need maximum compatibility (old hardware, embedded systems, anything before 2010).
AAC (Advanced Audio Coding) was designed in the late 1990s as the successor to MP3. It compresses audio about 20–30% more efficiently — meaning a 128 kbps AAC file sounds roughly as good as a 192 kbps MP3.
Apple bet hard on AAC: iTunes Store, Apple Music, and the iPhone's voice memos all use it. YouTube also uses AAC for its video audio tracks. MP3 stuck around because it's older, completely patent-free since 2017, and supported by literally everything.
| Feature | AAC | MP3 |
|---|---|---|
| Quality at same bitrate | Better | Baseline |
| File size (3-min song at perceived "transparent") | ~3 MB at 128 kbps | ~4.5 MB at 192 kbps |
| Released | 1997 | 1993 |
| Patent status | Patent-encumbered (royalties) | Patent-free since 2017 |
| iPhone / Apple Music | Native | Plays |
| Android | Plays | Plays |
| YouTube audio | Native (in MP4) | Not used |
| Hardware support | Modern devices | Universal |
| Multichannel (5.1) | Yes | Limited |
Use AAC when
- You're saving audio for an iPhone, iPad, or Apple Music library.
- You're encoding video soundtrack for YouTube, MP4 delivery, or any modern video pipeline.
- You want the smallest possible file at high quality.
- You're distributing a podcast or audiobook to modern players.
Use MP3 when
- You're sharing with someone who may have legacy hardware (car stereo from 2008, cheap MP3 player).
- You're burning a CD or embedding in firmware.
- You need a fully patent-free distribution (open source projects, archival storage).
- Your audience is mixed and "everyone's grandma can play it" matters more than file size.
Convert between AAC and MP3 in your browser
FAQ
- Is AAC really better than MP3?
- At the same bitrate, yes. At 128 kbps, AAC sounds noticeably cleaner on cymbals, reverb tails, and stereo imaging. At 256 kbps+ both are essentially transparent and the difference disappears.
- Does my car stereo play AAC?
- Cars made after roughly 2012 usually do. Older head units (especially CD changers) may only handle MP3 and WMA. If in doubt, convert to MP3 for car use.
- Why does iTunes / Apple Music use AAC?
- Apple licensed AAC early and built their entire ecosystem on it. Apple Music streams 256 kbps AAC. Their proprietary "Apple Lossless" (ALAC) is a separate, lossless format.
- Will converting MP3 to AAC improve quality?
- No. The lossy compression already happened. Converting MP3 to AAC just re-compresses already-degraded audio — usually slightly worse than the source. Keep the original if you can.