Audio Units

Audio Units (AU) are a system-level plug-in architecture provided by Core Audio in Apple's macOS and iOS operating systems. Audio Units are a set of application programming interface (API) services provided by the operating system to generate, process, receive, or otherwise manipulate streams of audio in near-real-time with minimal latency. It may be thought of as Apple's architectural equivalent to another popular plug-in format, Steinberg's Virtual Studio Technology (VST).

Because of the many similarities between Audio Units and VST, several commercial and free wrapping technologies are available (e.g. Symbiosis and FXpansion VST-AU Adapter). Celemony Software and PreSonus have also developed the Audio Random Access (ARA) extension, which works for both AU and VST, allowing greater integration between the plug-ins and DAW software.^[1]