Loopbacker

A virtual audio loopback device for macOS.

---

Loopbacker creates a virtual audio device on macOS that routes audio from any app's output directly to an input stream. Set it as your output device, and anything playing through it becomes available as a mic input -- perfect for capturing desktop audio in Discord, OBS, or any recording app.

How it works

App A (e.g. Music.app)           App B (e.g. Discord)
       |                                ^
       | output                         | input
       v                                |
   +---+--------------------------------+---+
   |           Lock-free Ring Buffer         |
   +----------------------------------------+

A CoreAudio HAL plugin provides the virtual device. A SwiftUI companion app handles driver installation and gives you a quick overview of the audio routing.

Install

From release

Download the latest .dmg from Releases, open it, and drag Loopbacker to Applications.

From source

Requires Xcode command-line tools and CMake (brew install cmake).

make all          # Build driver + app
make install      # Install driver (sudo) + app to /Applications

Uninstall

make uninstall    # Remove driver + app

Usage

1. Open Loopbacker.app and click Install Driver (requires admin).
2. Open System Settings > Sound and set the output device to Loopbacker.
3. In your recording/chat app, select Loopbacker as the input device.
4. Audio played to the Loopbacker output is now captured on its input.

Project structure

loopbacker/
├── Driver/          CoreAudio HAL plugin (C++17, CMake)
├── App/             SwiftUI companion app (Swift 5.9)
├── scripts/         Install/uninstall helpers
└── docs/            Architecture docs

Requirements

• macOS 11+ (Big Sur or later)
• Apple Silicon or Intel (universal binary)
• CMake 3.20+

License

FSL-1.1-MIT -- free to use for any non-competing purpose, converts to MIT after 2 years.