BlackHole vs a per-app routing app: when DIY routing is worth it

BlackHole is a free virtual audio cable, not a per-app router. It moves audio from one app into another with zero added latency, but it has no interface and no per-app controls — you build the routing yourself in Audio MIDI Setup. DIY routing with BlackHole is worth it when you need to capture sound, like recording system audio into a DAW or OBS. If you just want one app on headphones while the rest plays on speakers, a per-app routing app does that as a single rule, with no virtual cables to wire up.

BlackHole comes up in almost every "route audio on a Mac" thread, and for good reason — it's free, open source under GPL-3.0, from Existential Audio, and rock solid. But it's easy to point someone at it for the wrong job. The most common mistake is reaching for BlackHole to send Spotify to your AirPods and Zoom to your speakers, then spending an evening in Audio MIDI Setup wondering why it fights you. That's not what it's for. This guide is the honest version: what BlackHole actually is, what DIY routing really takes, and when it beats a dedicated routing app — and when it doesn't.

What BlackHole actually is

BlackHole is a virtual loopback driver. After you install it, macOS shows a new audio device called "BlackHole 2ch" (or 16ch, or 64ch) alongside your real speakers and headphones. Anything sent into that device becomes available as an input to other apps — it's a length of virtual cable between two jacks. It adds no processing delay, and it ships in 2-channel, 16-channel, and 64-channel builds for everything from a stereo recording to a 64-track studio routing.

The part people miss: BlackHole has no window, no menu-bar icon, and no volume or routing controls of its own. It does exactly one thing — carry audio — and leaves the wiring to you. The wiring happens in Audio MIDI Setup, the macOS utility where you create Multi-Output and Aggregate devices to combine BlackHole with a real output. BlackHole is the cable; Audio MIDI Setup is the patchbay; you're the engineer.

What "DIY routing" with BlackHole actually involves

A typical setup looks like this. You install BlackHole, open Audio MIDI Setup, and create a Multi-Output Device that plays to both your speakers and BlackHole at once. You point an app — or the whole system — at that Multi-Output device, then have a recorder or another app listen to BlackHole as its input. To monitor what's being captured, you often add an Aggregate Device so you can still hear it. It works, it's free, and people who do this often swear by it.

The honest catch is friction. Multi-Output devices don't have their own volume control and can break the volume keys. Drift between devices on an Aggregate needs a clock source set correctly or you get clicks. And the biggest limit: BlackHole routes system or per-app output into a capture path — it does not, by itself, give every app its own destination device. Many apps have no output picker at all, so "send only this app to that speaker" still isn't something BlackHole solves on its own. For the volume side of the same problem, see how to control individual app volume on a Mac.

When DIY routing with BlackHole is worth it

BlackHole is the right tool when the job is capturing or piping audio, not everyday device assignment. It shines when you need to:

Record system audio into a DAW (Logic, Ableton, GarageBand) or an editor. Pull desktop sound into OBS or Zoom for a screen share or stream. Feed one app's output into another app as an input. Build multi-channel routing for a podcast or a live show where you genuinely need 16 or 64 channels. In all of these, the value is the loopback path itself, and the one-time setup pays off because you reuse the same rig every session. If you like tinkering and your need is capture, BlackHole is excellent and free — there's no reason to pay for that.

When a per-app routing app wins

The other half of "routing" is simpler and far more common: this app comes out of that device. Music on AirPods, calls on a headset, alerts on the desk speakers, set once and forgotten. BlackHole isn't built for that — it has no concept of "per app," and wiring it to fake one is a lot of Audio MIDI Setup for a result that doesn't persist cleanly. A per-app routing app does exactly this at the OS level: each app gets a destination device, independent of the system default, and it sticks across restarts. Options here include Background Music (free, open source), SoundSource by Rogue Amoeba (around $49 one-time, deep controls plus EQ), and Fader (keyboard-driven, $19.99 one-time).

None of these replaces BlackHole for capture, and BlackHole doesn't replace them for everyday routing. They're different tools. The mistake is using one where the other fits.

Where Fader fits

Fader is a per-app routing app, not a virtual cable. You open the Routing tab, pick an output device per app from a dropdown, and it persists — no Multi-Output juggling, no clock sources. Because Fader also handles per-app volume from the keyboard, the same app covers both halves: how loud each app is and where it comes out. You hit a hotkey, the keyboard becomes a mixer, and you ride levels with letter keys without leaving what you're doing. It's a $19.99 one-time purchase with a 3-day free trial, no account, on macOS 14.4 or later.

It's also fair to say where Fader doesn't compete: it won't capture system audio into a DAW or hand you 64 channels of loopback. If that's your job, install BlackHole and enjoy it. For a step-by-step on everyday routing, see how to send one app's audio to a different output on Mac.

Bottom line

BlackHole is a free, excellent virtual cable for capturing and piping audio — recording system sound, feeding OBS, building multi-channel routing. It is not a per-app router, and forcing it to act like one means a lot of Audio MIDI Setup for a fragile result. If your real need is "this app on headphones, that one on speakers," a per-app routing app sets that as a rule in seconds. Use BlackHole for capture; use a routing app for everyday per-app output. If you want fast per-app volume in the same tool, that's Fader's lane.