oto.
Per-app volume mixer for your menu bar.
oto. is a lightweight macOS menu bar utility that lets you adjust volume levels and mute states independently for each running application.
Whether you are chatting on Discord while listening to background music or watching a tutorial during work, oto. gives you effortless control over your soundscape.
Why I Built It: The Frustration of Mixed App Volumes
Working on a Mac often means having multiple audio-producing apps open at once. Inevitably, you run into situations where you want Discord voices to be clearer, while YouTube or Spotify plays quietly in the background.
Every app outputs audio at different levels, and each person has their own ideal balance. Yet macOS only offers a single system-wide volume slider. Being unable to fine-tune volume on a per-app basis was a constant friction point for me.
While third-party mixers exist, most of them rely on heavy virtual audio drivers or overwhelm you with complex, cluttered interfaces. I wanted something clean, lightweight, and immediately intuitive.
That desire led me to build oto.—a volume mixer that lives unobtrusively in your menu bar and just works.
Key Features
Crafted for everyday comfort with a focus on simplicity and native macOS polish:
- Instant Menu Bar Access: Click the icon to view active audio-playing apps and their volume sliders at a glance.
- Fine-Grained Volume & Mute: Smoothly adjust individual levels with responsive sliders, or mute and reset to 100% with a single click.
- Per-App Output Routing: Direct Discord audio to your headset while keeping music or tutorials on your external monitor or speakers.
- No Virtual Audio Drivers: Built on Apple's Core Audio Process Tap API, ensuring low latency, high stability, and zero kernel extensions.
- Persistent Preferences: Your volume settings are remembered locally per app across sessions.
- Privacy by Design: Audio is processed entirely in memory on your Mac. No network calls, no telemetry, and no audio recording files.
A quiet companion designed to sit peacefully in your menu bar, ready whenever you need to adjust your mix.