AU / SND (Sun audio)
Also known as: Sun audio, .au file, .snd file, NeXT audio
AU (.au, also .snd) is a legacy audio format from Sun Microsystems and NeXT, common on early Unix systems and the old web. It is a simple container, often holding basic PCM or μ-law audio, and is now obsolete — files are typically converted to MP3 or WAV for modern playback.
- Legacy Sun/NeXT Unix audio format
- Often holds 8-bit μ-law or PCM audio
- Obsolete; converted to MP3 or WAV today
A legacy Unix format
The .au (and .snd) format dates to Sun Microsystems and NeXT workstations and was widely used for system sounds and early web audio. It is a minimal container, frequently storing 8-bit μ-law or plain PCM audio.
By modern standards the audio is low quality and the format is essentially obsolete, but you still encounter .au files in old archives, Unix software, and historical web pages.
Playing and converting AU
Cross-platform players like VLC still open .au files, and many audio tools recognize them. Phones and consumer media apps generally do not.
To use an old .au clip today, convert it to MP3 or AAC for small, compatible files, or to WAV to keep it uncompressed.