AAC file format
Advanced Audio Coding
AAC is MP3's successor: better sound at the same bitrate. It's the audio inside most MP4 videos, Apple Music and YouTube. Raw .aac files are a bare stream; M4A wraps AAC in an MP4 container.
| Property | AAC |
|---|---|
| File extensions | .aac |
| MIME type | audio/aac |
| Introduced | 1997 by MPEG (Dolby, Fraunhofer, AT&T, Sony, Nokia) |
| Compression | Lossy |
| Typical bitrate | 96–256 kbps |
| 3-minute song | ≈ 3.6 MB at 160 kbps |
| Tags and cover art | Limited in raw .aac (full in M4A) |
| Compatibility | Very wide: Apple, Android, YouTube, browsers |
| Best for | Efficient music and video soundtracks |
What is an AAC file?
AAC (Advanced Audio Coding) was standardised in 1997 as part of MPEG-2 and later MPEG-4, designed to replace MP3. It achieves better quality at the same bitrate, especially below 128 kbps. A .aac file is usually a raw ADTS stream; the same audio inside an MP4 container is called M4A.
Strengths and weaknesses
AAC is efficient and nearly universal — it's the default audio for iPhones, YouTube and most streaming services. Raw .aac files lack proper tags and seeking information, so M4A is usually the better container for music.
When should you use AAC?
Use AAC (preferably in M4A) for music libraries and podcasts, and as the audio track in MP4 videos.