What is .AU file extension?
Audio file created by Audacity, a free, cross platform audio editor; uses a proprietary format that can only be opened by Audacity; saved as one of multiple audio data files for an Audacity project (.AUD).
When you created a project in Audacity and import audio files, the audio data is converted to the AU format and is stored in a folder with the project called myproject_data, where the project name is myproject.aud. When done editing a project, you can export the audio to several standard formats, including .MP3, .WAV, and .M4A.
NOTE: Audacity's AU format is not compatible with the standard AU audio file format.
You can see a list of software programs here on www.easyfileopener.org that can open this file type so that you don’t need to search for it on the web. You can then open your file with this extension using a software listed below.