What is a .au file?
Sun Audio · Audio · Sun Microsystems / NeXT · 1992
An .au file is Sun audio, one of the oldest digital sound formats, from Unix workstations and early Java. It starts with the marker .snd and usually holds simple uncompressed or mu-law encoded sound.
What is a .au file used for?
AU files begin with the four bytes .snd and a short header giving the encoding and sample rate. They were the standard sound format on Sun and NeXT systems and in early Java applets.
The format is legacy now. VLC and Audacity open it; convert to WAV or MP3 for modern use.
How to open a .au file
The .au 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 .au file.
Windows
- VLC
- Audacity
- foobar2000
macOS
- VLC
- Audacity
- QuickTime
Linux
- VLC
- Audacity
- ffmpeg
How to convert a .au file
You can convert a .au file to wav, mp3, flac using a conversion tool or the export menu of an app that opens it.
.au file signature (magic bytes)
Programs recognise a .au file by the bytes at the start of the file, not by its name. These are the signatures for AU. For a full breakdown, see the AU file signature page.
| Hex signature | Offset | Note |
|---|---|---|
| 2E 73 6E 64 | 0 | '.snd' |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .au file?
An .au file is Sun audio, one of the oldest digital sound formats, from Unix workstations and early Java. It starts with the marker .snd and usually holds simple uncompressed or mu-law encoded sound.
How do I open an .au file?
Play it in VLC or open it in Audacity. To use it elsewhere, convert it to WAV or MP3.
What is a .au file?
Sun audio, an old Unix and Java sound format that starts with the .snd marker. It is largely historical today.
Is .au the same as .snd?
Effectively yes. The format's magic bytes are .snd, and some systems used the .snd extension for the same Sun audio format.
Related formats
Sources
Details on this page were checked against authoritative references: