Whether to record system audio, process an application’s sound output with another application, or share app audio, you need a virtual audio loopback driver, which creates virtual audio devices that can be used to pass around sound as needed.

BlackHole is an open-source audio loopback driver that makes this possible without the need for a kernel extension. This is especially important on Apple Silicon devices, where installing kernel extensions is more difficult and risky.

The driver is very simple to set up. All you need is to follow the wizard and restart your Mac. Two virtual input and output devices will then be available, and they can be used by various applications to record or route audio.

You get a choice of channel count, anywhere from 2 to 256, though compiled installers are only available for up to 64 channels. Of course, you can just compile the code yourself to use more channels. If you’re not sure which to download, the 2-channel version is your best bet.

Now that you’ve set it up, you can open Audio MIDI Setup to configure the devices and route sound. You can customize the volume and sample rate, but most use cases will require you to set up a multi-output device.

For instance, to record system audio, you need to create a multi-output device, configure it so that both BlackHole and your speakers/headphones output audio, and set the multi-output device as the system output device.

The virtual BlackHole input device will then capture system audio, and if you select it as the input in any recording application, you can record whatever you hear on your Mac. Detailed instructions are available for this use case, and many others, on the project’s GitHub page.

There are numerous potential applications for this driver, and it’s remarkably straightforward to configure. The channel count options and customizability make it highly versatile, and you can easily set it up for any purpose thanks to the detailed documentation.