What is a virtual audio device, and do you actually need one?

A virtual audio device is a software-only input or output that macOS and your apps treat as if it were real hardware — but it connects to no speaker or microphone. It just carries sound from one app to another inside your Mac, like a patch cable made of code. You need one when you have to capture or reroute audio between programs (recording system sound, feeding an app into OBS). If you only want per-app volume or to send an app to a different speaker, you probably don't.

"Virtual audio device" is one of those terms that sounds far more technical than the idea behind it. The reason it exists comes down to a single fact about how macOS handles sound: apps don't talk to your speakers directly. They talk to a device. Understand that, and every virtual device — BlackHole, Loopback, aggregate devices — snaps into focus, and so does the question of whether you actually need one.

What "device" means to macOS

On a Mac, every bit of audio flows through Core Audio, the system's audio engine. Core Audio thinks in devices: your built-in speakers are a device, your AirPods are a device, a USB interface is a device. When an app plays sound, it hands that sound to whichever output device is selected — and macOS mixes everything heading to the same device into one stream.

That's the whole reason the system feels rigid. An app can pick a device, but it can't easily reach inside another app's stream, and you can't point one app at "a recorder" or "another app," because those aren't devices macOS knows about. So people invented devices that aren't physically there.

So what is a virtual audio device?

A virtual audio device is a driver that presents itself to macOS as a normal input and/or output, complete with channels and a name in your Sound settings — except there's no hardware on the other end. Whatever an app sends into it comes straight back out of it, available to any other app that listens.

The cleanest mental model is a virtual patch cable. In a studio, you'd run a physical cable from one box's output to another box's input. A virtual audio device does the same routing, but the "cable" is software and the "boxes" are apps. Set an app's output to the virtual device, point a recorder's input at the same virtual device, and the recorder now hears that app. Nothing left your Mac; nothing came through a real jack.

This is a routing tool, not a volume tool. It's about where sound goes, which is a different problem from how loud each app is. If the distinction is fuzzy, our plain-English explainer on what audio routing on a Mac actually means lays out the two side by side.

The virtual audio devices you'll actually meet

A handful come up again and again. They split into two camps: pure "cables" that just move audio, and macOS's own combined devices that gang real hardware together.

BlackHole, from Existential Audio, is the reference example of a bare cable: it's free, open source, and passes audio between apps with near-zero added latency. It has no controls at all — no sliders, no mixing — because that's not its job. It's plumbing.

Loopback, from Rogue Amoeba, is the polished, paid take: instead of a fixed cable, you drag app and hardware sources onto a canvas and it builds a virtual device that combines them. Powerful, and priced like a pro tool at $99. Aggregate and Multi-Output devices are macOS's own, created for free inside Audio MIDI Setup; they gang real hardware together rather than tap app audio, but they live in the same "device that isn't one box" family.

What virtual audio devices are great at

When your goal is to capture or combine audio streams, virtual devices are the right tool and often the only one:

• Recording system or app audio. Screen recorders and podcast tools can't grab desktop sound on their own; a virtual device gives them an input to listen to.
• Streaming. Routing game audio, a call, and music into OBS as separate sources is a classic virtual-device job.
• Feeding one app into another. Piping a music app into a DAW, or a browser into a transcription tool, needs a shared virtual input.

In all of these, the point is moving a stream somewhere macOS won't send it by default. That's real, and no amount of per-app volume tweaking replaces it.

Where they get painful

The cost of a virtual device is setup and mental overhead. A bare cable like BlackHole has no volume of its own, so once your speakers are set to it you can't hear anything until you build a Multi-Output Device to also play through your real speakers — a common first-time "why is everything silent?" moment. You're now managing two or three devices, remembering which app points where, and re-selecting outputs whenever you plug in headphones. It's a driver install and a diagram, not a slider.

That's fine when routing is genuinely what you need. It's overkill when it isn't — and a lot of people reach for a virtual device to solve a problem that was never a routing problem.

Do you actually need one?

Here's the honest split. Ask what you're actually trying to do:

• "I want to record or stream this app's sound" / "combine two sources into one input." Yes — that's exactly what virtual audio devices are for. Start with BlackHole (free) and add a Multi-Output Device so you can still hear.
• "I want this app quieter than that one" / "mute one app" / "send an app to a different speaker." No — you don't need to build or manage a virtual device for that. macOS gained a modern audio framework in 14.4 that lets an app read and adjust another app's audio directly, which is the foundation Fader is built on.

That second case is where most people land, and it's where a virtual device is the wrong shape of tool. Fader gives every running app its own volume and its own output device without asking you to install a driver, draw a routing diagram, or juggle aggregate devices — and you set levels from the keyboard rather than a menu. If you specifically want per-app output without the virtual-cable dance, we walk through it in per-app audio output on Mac without Loopback or virtual cables.

None of this is a knock on BlackHole or Loopback — they're excellent at the capture-and-combine work they're designed for, and for a streaming rig they're often exactly right. The mistake is only reaching for a virtual device when your real need was "control the mix," which macOS can now do without one.

Bottom line

A virtual audio device is a software cable: an input/output with no hardware behind it, used to carry sound between apps. If you need to capture, stream, or combine audio streams, you want one — BlackHole is the free place to start. If you just want per-app volume, muting, or per-app output, you don't need to build one at all; a modern per-app mixer does it with less setup and no drivers to babysit. Match the tool to the verb: route means virtual device, mix means mixer.