Windows has had a per-app volume mixer for 15 years. macOS still doesn't. Fader fixes that: set any running app's volume straight from your keyboard — one letter per app — route each app to its own output device, and save mixer setups you can recall instantly. It lives in your menu bar, handles up to 10 apps at once, and is fully App Store sandboxed — no cloud, no account, no audio drivers to install.