Plugin Formats: Differences between VST, VST3, AU, AAX, RTAS, TDM

When you come to think about music plugins, you will inevitably see that there are numerous different formats. Today, we focus on VST, VST3, AU, AAX, RTAS, TDM.

When buying plugins you want them to be compatible with your music production software.

How to choose which format you want to use? In this article, we explain the differences between different formats to you.

In 1996, Steinberg, maker of Cubase, introduced VST. The technology lets developers provide instruments and effects that load inside a compatible DAW.

Several established plugin formats now serve different hosts. Choosing between them starts with the software you use to record and produce music.

VST/VST3

VST (Virtual Studio Technology) lets a DAW load third-party instruments and effects. VST2 and VST3 are different plugin formats, rather than quality settings. Many hosts support both, but you need the format supported by your particular DAW version. Apple’s Logic Pro and GarageBand use Audio Units instead, while Pro Tools uses AAX.

VST3 is the current branch of Steinberg’s plugin technology. The VST 3.8 development kit uses the MIT open-source licence. That licence covers the development framework: it does not make every VST3 instrument or effect free. A plugin developer can still sell a full licence, offer a subscription, or provide a limited trial.

For a new setup, choose VST3 when your DAW and plugin both support it. VST2 remains useful for older projects and instruments, but support is host-specific. Cubase and Nuendo 14 and 15 disable VST2 by default; their native Apple Silicon versions cannot load VST2. Ableton Live supports 64-bit VST3 from Live 10.1 onward and also supports compatible 64-bit VST2 plugins.

A Windows plugin will not run on a Mac simply because both downloads say VST3. Choose the correct operating-system installer and processor support as well as the format. Linux also needs an explicitly supported Linux build and a compatible host. A Windows DLL is not a native Linux plugin.

Keep the plugin format consistent when reopening or sharing a project. Switching an existing VST2 instance to VST3 is not always automatic, and installing the newer format does not guarantee that the old instance will load. Keep a backup and render important tracks to audio before retiring an older plugin.

AU

Audio Units (AU) is Apple’s plugin technology. Logic Pro and GarageBand use it for compatible third-party effects and instruments. AU is not the only plugin format available on a Mac: other Mac DAWs can support VST3, and Pro Tools uses AAX. The host determines which format you should install.

For a plugin offered in both AU and VST3, the musical controls may be very similar. The important difference is whether your DAW can load that build. Installing AU does not add VST support to Logic, and renaming a plugin file cannot convert its format.

Check whether the developer supplies AUv2 or AUv3 and whether your host supports it. AUv3 also appears in supported iPhone and iPad apps, but a Mac licence or installer does not automatically include an iOS version. Check the developer’s platform and purchase terms before assuming you can use the same product on both.

On Apple Silicon, look for native support for your processor and macOS release. Apple documents Rosetta support for compatible Intel Audio Units in Logic Pro, but that does not mean every old plugin will work. Use the developer’s current installer and compatibility list rather than relying on an old wrapper.

If you move an Ableton project between Mac and Windows, AU instances will not load on Windows. Where both systems support the same plugin, use a matching VST version for future shared projects. Render existing AU tracks to audio when the other computer cannot load them.

RTAS and TDM

RTAS (Real-Time AudioSuite) and TDM (Time Division Multiplexing) are legacy Pro Tools plugin formats from Digidesign, now Avid. RTAS uses the computer’s processor. TDM plugins run on compatible dedicated DSP hardware, which was useful in studio systems built around that hardware.

Pro Tools 10 belongs to the transition between those older formats and AAX. Pro Tools 11 moved to a 64-bit application and does not load RTAS, TDM or 32-bit AAX plugins. This is the important compatibility boundary when reopening old sessions, rather than the claim that a particular Pro Tools 10 maintenance update converted all old plugins.

An AAX update is a separate compatible build of a plugin; it does not make a TDM or RTAS file readable by modern Pro Tools. Check whether the original developer offers a 64-bit AAX version and whether the upgrade is included in your licence. Keep the old system or print the processed tracks to audio if an essential plugin has no supported replacement.

Hardware requirements matter too. Owning a TDM licence does not give you a modern AAX DSP version, and an old DSP card cannot be assumed to work with a current computer or Pro Tools release. Preserve working legacy sessions before changing the operating system, hardware or plugin licences.

AAX

AAX (Avid Audio Extension) is the plugin format used by current Pro Tools systems. It is available on Windows and macOS in compatible 64-bit builds. Choose AAX for Pro Tools rather than buying a VST3-only or AU-only instrument and expecting it to load directly.

AAX Native runs on the host computer. AAX DSP runs on compatible Avid DSP hardware, including supported HDX and Carbon systems. AAX AudioSuite provides file-based, non-real-time processing. These are different processing routes, and a plugin offered as AAX Native is not automatically available as AAX DSP.

AAX is not an upgrade that makes every plugin sound better than its VST or AU version. Choose it because your Pro Tools workflow requires it. For a session moving between native and DSP systems, verify that the actual plugins have the matching versions and licences; the shared format alone does not supply a missing DSP build.

On a Mac with Apple Silicon, also check native AAX compatibility for each plugin. The format name alone does not establish processor support. Install the developer’s supported version and test your essential sessions before replacing an older setup. For more on the host itself, see Pro Tools.

Summary

Your DAW is the starting point: use AU for Logic Pro or GarageBand, AAX for Pro Tools, and a supported VST format for hosts that use it. Then check your operating system, processor, plugin version and licence. Those checks prevent the common mistake of buying the right instrument in a build your computer cannot load.

Use VST3 for a new compatible setup, while keeping older formats where a working project needs them. If you share sessions, agree on the plugin versions and formats or render tracks to audio. The correct format makes the plugin usable; it does not decide the musical quality of the instrument or effect.