What is an AU (Audio Unit)?

An AU, or Audio Unit, is a plugin format developed by Apple that allows software instruments and audio effects to run inside compatible digital audio workstations (DAWs) on macOS and iOS systems. Audio Units enable producers and musicians to expand the capabilities of their music production software by adding additional sound generators and audio processing tools.

Audio Unit plugins can function as virtual instruments that generate sound, such as synthesizers or samplers, or as audio effects that process existing audio, including tools like equalizers, compressors, reverbs, and delays. These plugins operate within host applications such as Logic Pro, GarageBand, and other macOS-compatible DAWs.

Because Audio Units are built directly into Apple’s Core Audio framework, they integrate efficiently with macOS and iOS systems. This tight integration makes AU plugins a common standard for music production on Apple devices, allowing developers to create high-performance audio tools that work seamlessly within Apple-based recording environments.