VST vs AU vs AAX: Plugin Formats Explained, with Install Folders for Mac and Windows

Audio Unit (AU) and VST are two plugin formats that usually contain exactly the same audio processing: AU is Apple's macOS-only format and the only one Logic Pro and GarageBand load, while VST (today, VST3) is Steinberg's cross-platform format used by most other DAWs. AAX is Avid's format, and it's the only one Pro Tools accepts.

So the choice between them is mostly made for you by your DAW. What you do need to know is which file goes where, because a plugin in the wrong folder or the wrong format simply won't show up.

What are AU plugins?

Audio Units are Apple's plugin system, built into macOS as part of its Core Audio framework. An AU plugin, sometimes written as an AudioUnit plugin, is a file ending in .component. Logic Pro and GarageBand only load AU, and most other Mac DAWs, including Ableton Live, FL Studio and Studio One, load them too.

macOS validates Audio Units before a host will use them. In Logic, a plugin that fails validation gets switched off; you can see its status, rescan it or turn it back on in the Plug-in Manager (Logic Pro > Settings > Plug-in Manager, called Preferences in older versions).

There's also AUv3, a newer version delivered inside an app rather than as a .component file. It's how plugins work on iPad and iPhone, and some Mac apps use it as well.

What is a VST plugin?

VST (Virtual Studio Technology) is Steinberg's format and the most widely supported one in music software. The current version is VST3, which uses a .vst3 file on both Windows and Mac. It's the format to use on Windows in almost every DAW except Pro Tools. For the history and the VST2 vs VST3 differences, read what is a VST plugin.

What is an AAX plugin?

AAX stands for Avid Audio eXtension. Avid introduced it with Pro Tools 10 to replace its older RTAS and TDM formats, and since Pro Tools 11 it's been the only plugin format Pro Tools loads. AAX files end in .aaxplugin and run on both Mac and Windows.

• AAX Native runs on your computer's CPU. This is what nearly everyone uses.
• AAX DSP runs on Avid's HDX hardware cards, used in larger studios for low-latency processing.
• AudioSuite isn't a separate format. It's Pro Tools' offline mode for AAX plugins, which renders the effect onto a clip instead of running it in real time.

AAX plugins also have to be digitally signed by the developer before a release version of Pro Tools will load them. That signing is separate from iLok copy protection, which some developers use and others don't. Our guide to installing plugins in Pro Tools covers what that means in practice.

Audio Unit vs VST vs AAX at a glance

Plugin install folders on macOS

These are the standard system-wide locations. Installers put plugins here by default, and DAWs look here automatically.

AU, VST3 and VST2 plugins can also live in the same folders inside your user Library (for example ~/Library/Audio/Plug-Ins/Components), where they're available to your account only. The user Library is hidden by default; in Finder, hold Option and open the Go menu to reveal it.

Plugin install folders on Windows

VST2 is the odd one out. It never had a fixed folder on Windows, so every installer asks where to put it, and you have to point your DAW at the same place. If you have old VST2 plugins, pick one folder, keep them all there, and add it to your DAW's plugin settings.

Does AU sound different from VST?

No. A developer writes the audio processing once and wraps it in each format. The AU and VST3 versions of the same plugin process the same audio identically. Any difference you think you hear is almost always a level difference or a different preset loaded.

There can be small practical differences, like how the DAW handles sidechain inputs or plugin delay reporting. On a Mac, the simple rule is: use AU in Logic, and in other DAWs pick whichever format you like and stick to it, so your plugin list doesn't fill up with duplicates.

Should you install all three formats?

Most plugin installers offer AU, VST3 and AAX (sometimes VST2 and CLAP too) as checkboxes. Install only what your DAWs use. If you run Logic and Ableton on the same Mac, the audio units vs VST question answers itself: AU for Logic, and either AU or VST3 for Live. If you also open sessions in Pro Tools, add the AAX plugins. Extra formats don't break anything, but they take up disk space and can double the entries in your plugin browser.

A free plugin is the easiest way to test your setup before you spend money. Pump, our free tempo-synced sidechain plugin, comes as VST3, AU and AAX, so you can confirm each of your DAWs finds it in the right place.

Plugin not showing up? Check these

• Wrong format for the DAW. A VST3 will never appear in Logic or Pro Tools, however many times you rescan.
• Wrong folder. Compare the plugin's location with the tables above. Installers sometimes offer a custom path that your DAW doesn't scan.
• Failed validation on Mac. Logic and other AU hosts skip plugins that fail validation. Check Logic's Plug-in Manager.
• The DAW hasn't rescanned. Quit and reopen it, or run a manual rescan. In Ableton, that's in the Plug-Ins tab of Settings; see our Ableton install guide.

Our plugins come as VST3, AU and AAX, so there's a version for whichever DAW you use. More Pro Tools specifics are on our Pro Tools page.