VST (Virtual Studio Technology) is a native framework that was developed by Steinberg. The plug-ins come in three types: VST Instruments, VST effects and VST MIDI effects. VST 3.4, which came out in 2011, is the current version. The majority of plug-ins are Windows only due to competing Audio Unit, which is built into the Mac OS. iZotope, Antares, Waves, Audified, and IK Multimedia all produce VST format plugins.