BlackHole 2ch

BlackHole 2ch is a two-channel macOS virtual audio loopback driver from Existential Audio. It routes audio between applications through Core Audio and is useful for screen recording, streaming, online meetings, and capturing system sound in a recording application. It is a driver, not a standalone recorder or a separate Applications-folder app.

Features

• Route stereo audio from one application's output into another application's input.
• Use the device from applications that accept Core Audio devices.
• Combine virtual routing with physical speakers through an Audio MIDI Setup Multi-Output Device.
• Work on Intel and Apple Silicon Macs without a kernel extension or reduced system security.
• Use supported sample rates and Core Audio's 32-bit floating-point audio format. The publisher describes zero additional driver latency; this is not a promise of zero end-to-end application or hardware latency. Other channel-count variants are separate packages; this listing installs two channels.

Installation and setup

Install brew install --cask blackhole-2ch, approve the package installation when requested, and reboot. Homebrew explicitly requires a reboot for the installation to take effect. The official installer can also be obtained from the publisher. Open macOS Audio MIDI Setup to verify BlackHole 2ch, select it as the source application's output and recording application's input, and match sample rates. For simultaneous monitoring, create a Multi-Output Device including BlackHole and the desired physical output. Review the publisher's routing instructions before changing the system-wide sound output.

Requirements, dependencies, and conflicts

The publisher documents macOS 10.10 Yosemite or later and builds for Intel and Apple Silicon. Windows, Linux, iOS, and Android are not supported by this macOS Core Audio driver. Homebrew's current cask declares no additional formula dependency, explicit macOS minimum, or package conflict. Applications must support selecting compatible audio devices; recording applications may request microphone permission. Administrative approval and a reboot may be needed to install the driver. No kernel extension or disabling macOS security is required.

Multi-Output compatibility is not universal: the official FAQ lists Apple Podcasts, Apple Messages, and HDHomeRun as known problematic applications. macOS does not provide a single volume control for a Multi-Output Device; adjust individual device volumes in Audio MIDI Setup. Keep built-in output enabled and first where required by the publisher's instructions. AirPods microphones use a lower sample rate and should not be the aggregate or multi-output clock device; use built-in speakers or BlackHole 2ch as the primary device. Matching sample rates and deliberate clock/drift settings help avoid routing problems. These are documented compatibility limits, not Homebrew package conflicts.

Accounts, costs, and license

No BlackHole account or subscription is required to use the installed driver. The publisher offers downloads and accepts optional support; download-site registration and redistribution terms are separate from runtime use. The current source LICENSE specifies GNU GPL v3.0 for source code, while official compiled binaries and installers are separately marked copyright, all rights reserved. Branding and trademarks are reserved separately. Do not assume the source license automatically grants permission to redistribute the official installer or branding.

Official references

• Repository and setup instructions
• Multi-Output guide
• Current license wording
• Official download page