VST3, AU and AAX
which one do you need?
Three names on every plugin box, and almost no way to find out which one applies to you without buying the wrong one first.
Short answer
What is the difference between VST3, AU and AAX?
They are three different ways for a plugin to talk to a DAW, and your DAW picks for you. Logic Pro takes AU, Pro Tools takes AAX, and nearly everything else takes VST3. The plugin inside is the same either way — the format is the connector, not the sound.
What a format actually is
A plugin is a small program your DAW loads and hands audio to. For that to work, both sides have to agree on the details: where the audio arrives, how parameters are named and automated, how the interface gets a window, how the plugin saves its state into your project.
A plugin format is that agreement written down. Three of them are in use, because three companies wrote one — Steinberg, Apple and Avid — and each host supports the ones it chose to support.
Nothing about the sound lives in the format. The same plugin built to all three formats does the same arithmetic to your audio in each.
VST3
Steinberg’s format, and the closest thing to a default. Ableton Live, Cubase, Studio One, Bitwig, Reaper and FL Studio all load VST3, on both macOS and Windows. If you use anything other than Logic Pro or Pro Tools, this is almost certainly the one you are using.
You will still see VST2 on older plugins. Steinberg stopped issuing licences for it in 2018 and hosts have been dropping it since; it is not a format worth chasing on anything new.
AU — Audio Units
Apple’s format, macOS only, and the only one Logic Pro and GarageBand will load. There is no Windows equivalent and there is no way around it: a Logic user needs the AU build, full stop.
AU is also what iOS hosts use, in a variant called AUv3, though that is a different distribution story to the desktop one.
AAX
Avid’s format, and the only one Pro Tools loads. It exists on both macOS and Windows.
AAX has historically been the hardest format for a small developer to ship, because Avid requires plugins to be signed with a certificate issued through their developer programme before Pro Tools will load them. That paperwork, rather than the technical work, is why plenty of good plugins never appear in Pro Tools.
So which do you need?
Find your DAW in the table below. If you work in more than one — writing in Live, mixing in Pro Tools — you need the formats for each, which is the usual reason people end up caring about this at all.
Pook builds all three from one plugin, so this is a question you answer once and then stop thinking about. The plugin you make while writing in Live is the same plugin that opens in the Pro Tools session.
| Format | macOS | Windows | |
|---|---|---|---|
| VST3Virtual Studio Technology 3Steinberg | Steinberg | Supported | Supported |
| AUAudio UnitsApple | Apple | Supported | Not supported |
| AAXAvid Audio eXtensionAvid | Avid | Supported | Supported |
| DAW | Loads | |
|---|---|---|
| Ableton LivemacOS & Windows | VST3 · AU | AU on macOS |
| Logic PromacOS only | AU | AU is the only option |
| Pro ToolsmacOS & Windows | AAX | AAX is the only option |
| CubasemacOS & Windows | VST3 | Steinberg’s own host — no AU |
| Studio OnemacOS & Windows | VST3 · AU | AU on macOS |
| BitwigmacOS & Windows | VST3 | |
| ReapermacOS & Windows | VST3 · AU | AU on macOS |
| FL StudiomacOS & Windows | VST3 · AU | AU on macOS |
More questions, answered
No. A plugin you build is not tied to one format — the same source produces VST3, AU and AAX. You pick the format at the point of loading it in a host, and Pook installs the ones your platform supports.
Avid built AAX around Pro Tools’ own audio engine, including the DSP hardware versions that ran plugins on dedicated cards rather than the computer’s processor. The format stayed even as the hardware became optional, and Pro Tools has never loaded VST3 or AU.
Not for anything new. Steinberg stopped issuing VST2 licences in 2018, and the hosts still loading it are doing so for compatibility with plugins that were never updated. Anything built today should be VST3.
It should not. The format governs how the plugin and the host exchange audio, parameters and state, not what happens to the samples in between. Differences people report usually trace back to the host — different delay compensation, different oversampling on the bus, or a different signal reaching the plugin in the first place.
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