Audio Units (AU) are a system-level plug-in architecture provided by Core Audio, a set of application programming interface services provided by Apple Computer's Mac OS X operating system. Those services allow to generate, process, receive, or otherwise manipulate streams of audio.

Mac OS X comes with Audio Units allowing to timestretch an audio file, convert its sample rate and stream audio over a Local Area Network. It also comes with a collection of AU plug-ins such as EQ filters, dynamic processors, delay, reverb, and a Soundbank Synthesizer Instrument.


AU are used by Apple applications such as GarageBand, Soundtrack, Logic Express, Logic Pro, and Final Cut Pro and most 3rd party audio software developed for Mac OS X.