Audio format
What is a .aac file?
AAC (Advanced Audio Coding) is a lossy audio codec designed as the successor to MP3. At the same bitrate it generally sounds better.
It’s the audio of most MP4 videos, Apple Music and YouTube. Bare .aac files are less common than AAC inside .m4a or .mp4.
fileclay opens and writes AAC
AAC vs MP3 vs Opus
| AAC | MP3 | Opus | |
|---|---|---|---|
| Compression | Lossy | Lossy | Lossy |
| Quality at low bitrates | Good | Fair | Very good |
| Playback | Almost everywhere | Everywhere | Browsers, modern apps |
| Best for | Apple devices, streaming | Sharing, podcasts | Voice calls, the web |
When to use AAC
Good for
- Audio for video
- Music on Apple devices
- Streaming at moderate bitrates
Not a good fit
- Master copies
- Very old players: MP3 is safer
- Audio you still plan to edit
How to open .aac files
| Platform | App | Notes |
|---|---|---|
| Windows | Media Player | Built in |
| macOS, iPhone | Music, Files | Built in |
| Android | Most music apps | Built in |
| Browsers | Chrome, Safari, Firefox, Edge | Drag the file into a tab |
| Any system | VLC | Free |
Convert AAC files
From AAC
AAC to MP3A second lossy pass.AAC to WAVLarger file. Lost detail doesn’t come back.AAC to OpusA second lossy pass.AAC to FLACLarger file. Lost detail doesn’t come back.AAC to OGGA second lossy pass.AAC to M4AA second lossy pass.
All 18 output formats: .mp3, .wav, .m4a, .ogg, .flac, .opus, .oga, .m4b, .aiff, .aif, .wma, .ac3, .mka, .caf, .au, .tta, .wv, .mp2
Conversions run in your browser. Files aren’t uploaded.
Questions about AAC
Is AAC better than MP3?
At the same bitrate, generally yes. MP3 plays in slightly more places.
What is the difference between AAC and M4A?
AAC is the codec and M4A is a container that usually holds it.
Is AAC lossless?
No. For lossless audio in the same container, Apple uses ALAC.
Does converting MP3 to AAC improve quality?
No. It adds a second lossy pass.