Virtual Audio Cable (VAC) is an audio bridge between applications that transmits sounds (audio streams) from app to app, from device to device.

VAC creates a set of virtual audio devices. Each device simulates an audio adapter (usually named a "card") whose output is internally connected to the input, making an audio loopback. If an application plays audio to the output of such device, the sound will not be audible because the signal is looped back to the input. But if another application records from the input, it receives the sound produced by the first app.

Such virtual devices are named Virtual Cables. The term "Virtual Cable" is used only in the description of VAC product, as a placeholder. Actual names of virtual audio devices/endpoints that you will see in applications' menus, are different (for example, "Line 1", "Line 2" etc.).

Each side of any Virtual Cable can be used by several audio apps at the same time. If two or more apps play sounds to the same playback endpoint, these sounds are mixed, and the result is transmitted to the recording side. It two or more apps record from the same endpoint, each app gets a copy of the sound.