AAC File Format (.aac)
An AAC file, in this raw form, holds an ADTS bitstream of audio compressed with Advanced Audio Coding, the codec MPEG standardized in 1997 as a successor to MP3 that delivers better quality at the same bit rate.
AAC at a glance#
| Full name | raw ADTS AAC (Advanced Audio Coding) |
|---|---|
| File extension | .aac |
| Category | Audio Files |
| Developer | Fraunhofer IIS, AT&T Labs, Dolby Laboratories and Sony |
| First released | 1997 |
| MIME types | audio/aacaudio/aacp |
| Compression | Lossy |
| Specification | ISO/IEC 14496-3 (MPEG-4 Part 3, Audio) |
| FileFlip support | FileFlip reads this format but does not write it |
What a .aac file can hold#
These are the things a AAC file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.
| Audio | Yes |
|---|---|
| Streaming | Yes |
Strengths and limitations of AAC#
What AAC does well
- Delivers noticeably better quality than MP3 at the same bit rate, particularly below 128 kbps
- ADTS frames are self-contained, which is why AAC is the default codec for streaming and broadcast
- The specification supports up to 48 full-bandwidth channels, far beyond MP3's stereo limit
- Free to stream, distribute or play; only developers of encoder or decoder software need a patent license
Where AAC falls short
- Raw ADTS AAC has no standard place to store tags, so artist, album and artwork metadata generally doesn't travel with a bare .aac file
- Most consumer software expects AAC inside an M4A or MP4 container rather than as a raw .aac stream
- Still lossy, so it shares the same one-way compression trade-off as MP3
Use raw AAC when a pipeline needs the bitstream itself, such as for streaming or broadcast, and per-file metadata isn't required.
Convert AAC to MP3 when a destination app or device doesn't support AAC playback, keeping in mind the conversion cannot add back what the original AAC encoding discarded.
How to open a .aac file#
A .aac file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts AAC into a format your machine already opens, and it does it in the browser tab rather than on a server.
| Platform | Programs that open it |
|---|---|
| Windows | Windows Media Player, VLC |
| macOS | Music, QuickTime Player, VLC |
| Linux | VLC, Audacious |
| iOS | Music, VLC |
| Android | VLC, the built-in media player |
| Web | FileFlip |
AAC questions people ask#
What's the difference between AAC and MP3?
AAC is a newer, more efficient lossy codec than MP3. Standardized in 1997 versus MP3's 1993, it uses better psychoacoustic modeling to sound cleaner than MP3 at the same bit rate, especially below 128 kbps. Both throw away audio data permanently, so neither is a lossless upgrade over the other.
Is a .aac file the same as an M4A file?
No. Both usually hold AAC-compressed audio, but a .aac file is a raw ADTS bitstream with no container around it, while .m4a is that same AAC audio wrapped in an MP4 container that adds proper metadata support, seeking and chapter markers. Most consumer software expects the M4A version.
Does converting AAC to MP3 lose quality?
Yes, converting AAC to MP3 loses quality, because both are lossy codecs and the conversion has to decode the AAC and re-encode it in MP3's different, also lossy, format. The result carries artifacts from two compression passes instead of one, an effect known as generation loss.
What plays AAC files?
Apple's Music and QuickTime Player, VLC, and every modern browser and mobile OS play AAC audio, since it's the default codec for iTunes, YouTube and most streaming services. A raw .aac file specifically is less universally recognized than the same audio in an M4A container, so some players need it renamed or re-wrapped first.
Why does my AAC file have no song title or album art?
A raw .aac file is just the ADTS audio bitstream with no defined place to store tags, so players can't show a title, artist or album art the way they can for an MP3 or M4A. Converting the audio into an M4A or MP3 container adds the missing space for that metadata.
Converting AAC files#
Convert AAC to another format
FileFlip does not write .aac files, so nothing on the site converts into this format. It works as a source only.
Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.