What is a .ac3 file?
Dolby Digital Audio · Audio · Dolby Laboratories · 1991
AC-3 is Dolby Digital, the surround-sound audio format used on DVDs, Blu-rays and digital TV. A .ac3 file holds a multi-channel soundtrack, typically 5.1, compressed for home cinema.
What is a .ac3 file used for?
Dolby Digital frames begin with the sync word 0B 77. AC-3 delivers up to 5.1 channels (five speakers plus a subwoofer) and is the standard cinema and broadcast surround format alongside its successor E-AC-3.
You usually meet AC-3 inside video files rather than on its own. Players like VLC decode it; converting to a stereo format helps on devices without surround support.
How to open a .ac3 file
The .ac3 format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list. For a step-by-step walkthrough, see how to open a .ac3 file.
Windows
- VLC
- foobar2000
- MPC-HC
macOS
- VLC
- IINA
Linux
- VLC
- ffmpeg
- mpv
How to convert a .ac3 file
You can convert a .ac3 file to wav, aac, mp3 using a conversion tool or the export menu of an app that opens it.
.ac3 file signature (magic bytes)
Programs recognise a .ac3 file by the bytes at the start of the file, not by its name. These are the signatures for AC-3. For a full breakdown, see the AC-3 file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| 0B 77 | 0 | sync word |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .ac3 file?
AC-3 is Dolby Digital, the surround-sound audio format used on DVDs, Blu-rays and digital TV. A .ac3 file holds a multi-channel soundtrack, typically 5.1, compressed for home cinema.
How do I open an AC3 file?
Play it in VLC, which decodes Dolby Digital. To play it on a stereo-only device, convert it to WAV or AAC.
Is AC-3 the same as Dolby Digital?
Yes. AC-3 is the technical name for Dolby Digital, the 5.1 surround format on DVDs, Blu-rays and broadcast TV.
Why is there an .ac3 file with my movie?
It is the surround-sound track, sometimes stored separately from the video. A player combines them, or you can mux it back into the video file.
Related formats
Sources
Details on this page were checked against authoritative references: