VST vs. AU vs. AAX: What's the Difference?

VST, AU, and AAX are plugin formats that allow virtual instruments and audio effects to work with a digital audio workstation (DAW). The main difference between them is which DAWs and operating systems they support.

VST has broad support across DAWs on Windows and macOS, AU is closely associated with Apple’s ecosystem, and AAX is designed for Pro Tools. The right format depends mainly on the DAW you use, your operating system, and your workflow.

This guide compares the three formats side by side, explains where each one works, and helps you decide which version to install.

VST vs. AU vs. AAX: Quick Comparison

VST, AU, and AAX all serve a similar purpose: they let audio plugins work within a DAW. However, each format is associated with a different ecosystem. VST, developed by Steinberg, is widely supported across DAWs. AU, developed by Apple, is primarily used on macOS. AAX, developed by Avid, is designed for Pro Tools. All three formats can support virtual instruments and audio effects, but compatibility varies by DAW and operating system.

VST vs. AU vs. AAX: What Is the Difference?

Each format is a set of technical rules that define how a plugin and a DAW communicate. Here's how each one works and where it fits.

VST (Virtual Studio Technology)

VST, or Virtual Studio Technology, was developed by Steinberg and is one of the most widely used plugin formats. It is supported by most DAWs on both Windows and macOS. VST plugins for Mac work just as well as they do on a PC, as long as your DAW supports the format.

When you open your DAW, it scans your system's plugin folders and loads the VST plugins it finds. A VST plugin communicates with the DAW so that the DAW can use the plugin as part of a music production or recording session. VST plugins can provide both virtual instruments and audio effects.

VST3 is the modern version of the VST format. If a plugin offers VST3, it may be the version recommended by the plugin developer or DAW. VST2 and VST3 have different technical features.

AU (Audio Units)

AU, or Audio Units, was developed by Apple as part of its audio technology. It is primarily associated with macOS and Apple’s ecosystem. DAWs like Logic Pro and GarageBand use AU plugins rather than VST.

AU isn't limited to Apple's apps, though. Some third-party DAWs on Mac, including Ableton Live, support AU alongside VST. A newer version, AUv3, also lets plugins run on iPhone and iPad.

Like VST, AU covers virtual instruments, audio effects, and other plugin types, such as MIDI effects. What it doesn't cover is Windows support. AU plugins only run on Apple platforms.

Mac users may see both VST and AU versions of the same plugin. This is because some Mac-compatible DAWs support VST, while others use AU. Having both formats available gives users more options depending on their DAW.

AAX (Avid Audio eXtension)

AAX, or Avid Audio eXtension, was developed by Avid for the Pro Tools ecosystem. It is primarily relevant to users working with Pro Tools.

AAX is available in AAX Native and AAX DSP variations and can be used for both virtual instruments and audio effects.

Importantly, having a VST or AU version of a plugin does not automatically make that plugin compatible with Pro Tools. Pro Tools users generally need the appropriate AAX version of the plugin.

How Are VST, AU, and AAX Different?

The key difference is where each format is supported and how it integrates with a DAW.

• VST has broad cross-DAW support.

• AU is strongly associated with Apple’s ecosystem and macOS.

• AAX is designed around Pro Tools.

Those differences come down to where each format can run. AU is part of Apple’s audio frameworks in macOS, so AU plugins run on Apple platforms and nowhere else. VST isn’t tied to one company’s operating system, and most DAWs on Windows and macOS support it. AAX plugins can be built by any developer, but Avid licenses the format for commercial release, and they load in Pro Tools and other Avid systems like Media Composer.

What the format doesn't decide is the sound. When a developer offers the same compressor, synth, or reverb in several formats, the versions are normally built from the same processing code and are designed to behave the same way. Small differences between formats are possible, but the plugin's own code is what shapes the sound.

Can the Same Plugin Be VST, AU, and AAX?

Yes, and many commercial plugins are. Developers often build the same instrument or effect in all three formats so it works in as many DAWs as possible, and a single purchase or license often covers every format.

During installation, you'll usually see checkboxes for each format. Each version installs to its own system folder, and your DAW only looks for the formats it supports. Pro Tools ignores VST3 and AU files, while Logic Pro ignores VST3 and AAX.

Not every plugin covers all three, though. Some smaller or free developers release only one or two formats, which is why it's worth checking a plugin's supported formats before you buy or download it. If you only use one DAW, you can skip the formats it can't load and keep your plugin lists cleaner.

Which Plugin Format Should You Use?

In most cases, your DAW makes this decision for you. Use these guidelines to match the format to your setup.

Choose VST If...

• Your DAW supports VST, like Cubase, Ableton Live, or FL Studio

• You work in more than one DAW and want the same plugins available in each

• You want the most broadly supported format

• You work across Windows and macOS, or share projects between the two

If a plugin offers both VST2 and VST3, VST3 is the current version and the safer default for a new setup.

Choose AU If...

• You're using a Mac

• Your DAW supports AU

• You're primarily working in Apple's ecosystem

• You're using Logic Pro, GarageBand, or another AU-compatible DAW

If you use Logic Pro or GarageBand, AU isn't just the preferred option but the only one those apps load. In Mac DAWs that support both AU and VST, either works, so choose based on your workflow and whether you share projects with Windows users.

Choose AAX If...

• You're using Pro Tools

• You need plugins specifically compatible with the Pro Tools environment

• Your plugin offers AAX Native or AAX DSP, and your system supports the appropriate version

For most Pro Tools users on a standard computer, AAX Native is the version you'll use. AAX DSP only comes into play if your setup includes Avid DSP hardware, like an HDX card or Pro Tools | Carbon.

VST vs. AU vs. AAX: Which One Is Best?

No single format is best for everyone, because each one leads in its own area:

• VST: Best for broad DAW compatibility across Windows and macOS

• AU: Best fit for Logic Pro, GarageBand, and other compatible Apple/macOS workflows

• AAX: The format to look for when you're using Pro Tools

The best format isn't universally the same. Your DAW, operating system, and workflow should determine which version you install. If you're not sure, check your DAW's plugin settings or documentation, then install only the formats it supports.

Which Format Does Your DAW Use?

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Frequently Asked Questions

Is VST Better Than AU?

Not in terms of sound or capability. VST and AU generally deliver the same audio quality and support the same kinds of instruments and effects, so the real difference is compatibility. VST works in more DAWs across Windows and macOS, while AU is required for Logic Pro and GarageBand.

Is AU Only for Mac?

AU is only for Apple platforms. It runs on macOS, and the AUv3 version also works on iPhone and iPad. AU plugins aren't compatible with Windows. If you share projects between Mac and Windows computers, VST is usually the better choice.

Is AAX Only for Pro Tools?

For music production, essentially yes. AAX was designed for Pro Tools, and other DAWs like Logic Pro, Ableton Live, and Cubase don't load it. Outside Pro Tools, it's used mainly in Avid's own products, such as Media Composer.

Do VST, AU, and AAX Sound Different?

No, not by design. A plugin's sound comes from its processing, not its format, so the VST3, AU, and AAX versions of the same plugin are built to sound the same. If you notice a difference, it's more likely caused by settings, plugin versions, or how a specific DAW handles the plugin.

Do I Need to Install VST, AU, and AAX?

Not usually. Install the formats your DAW loads and skip the rest. More than one format makes sense if you use several DAWs that read different formats, such as Logic Pro (AU) and Pro Tools (AAX), or if you open the same sessions on Mac and Windows. For example, using VST3 instead of AU in Ableton Live on a Mac keeps the project loadable on a Windows computer. Installing formats you don't use won't improve the sound and can add duplicate entries to your plugin list.

Can I Use a VST Plugin in Pro Tools?

Not directly. Pro Tools only loads AAX plugins, so the simplest solution is to install the plugin's AAX version if the developer offers one. Third-party wrapper tools can host VST plugins inside Pro Tools, but they add an extra layer of complexity, so it's worth checking for an AAX version first.