File Extensions AU File Format SUMMARY: AU files are audio files popular on the Solaris and Unix platforms.   Files with the AU extension contain audio data. This file format was created by Sun Microsystems. In this way, WAV files are similar to the WAV files, but are found most often on Sun, Unix, and Linux-based systems. Since they are uncompressed audio files they take up much space on a hard drive; thus, you will most likely only see them used for small sound effects rather than entire songs. Windows users: NOTE that unless you have configured your computer with the file extension viewing tweak, it is possible that a filename that looks like it ends with ".au", especially one attached to an e-mail message, actually has a hidden OTHER extension, meaning that if you double-click the file, it may actually run a computer virus!   Add: Del.icio.us | Digg | Furl | My Yahoo!   Discuss This Tip Print This Tip Get E-Mail When New Tips are Online Return to the File Extensions page.