VolC

VolC is a small native macOS menu bar app for controlling app audio where macOS exposes a safe public path to do it.

The app is intentionally simple: no virtual audio devices, no kernel extensions, no third-party dependencies, and no microphone capture.

Screenshots

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Status

VolC is usable, but it is also honest about macOS limitations. Public CoreAudio HAL can enumerate apps that are producing audio, but it does not provide a public writable per-process gain control. For that reason, VolC uses CoreAudio for discovery and falls back to AppleScript for apps that expose scriptable volume controls.

Compatibility

• Runtime target: macOS 13 Ventura or newer
• Current maintainer test machine: macOS 15.7.1 Sequoia
• UI: SwiftUI + AppKit menu bar popover
• Audio discovery: CoreAudio HAL
• Launch at login: SMAppService

See docs/COMPATIBILITY.md for macOS and Xcode guidance. If the Mac App Store says the newest Xcode requires a newer macOS version, use Apple's developer downloads page to install a compatible older Xcode.

Supported Per-App Controls

App	Bundle ID	Support level
Spotify	com.spotify.client	Uses Spotify's AppleScript sound volume property
Music	com.apple.Music	Uses Music's AppleScript sound volume property
Google Chrome	com.google.Chrome, com.google.Chrome.helper*	Sets reachable audio and video element volume in Chrome tabs
Microsoft Edge	com.microsoft.edgemac, helper processes	Sets reachable audio and video element volume in Edge tabs
Brave	com.brave.Browser, helper processes	Sets reachable audio and video element volume in Brave tabs
Vivaldi	com.vivaldi.Vivaldi, helper processes	Sets reachable audio and video element volume in Vivaldi tabs
Opera / Opera GX	com.operasoftware.Opera*, helper processes	Sets reachable audio and video element volume in Opera tabs
Safari	com.apple.Safari	Sets reachable audio and video element volume in Safari tabs

Browser support requires Allow JavaScript from Apple Events in that browser. Browser support does not reach cross-origin frames, native browser UI sounds, DRM media that blocks script access, or browsers without compatible AppleScript automation.

Apps without AppleScript support are shown as read-only because public HAL discovery can see them, but public HAL cannot set their individual output gain.

Known read-only categories include Zoom, Discord, Firefox, most games, and most Electron apps. These apps can usually be detected while producing audio, but VolC cannot change their individual system output volume without using a virtual audio device or private API.

Build and Run From Xcode

1. Install a compatible Xcode. See docs/COMPATIBILITY.md.

2. Clone the repo:

   git clone https://github.com/Bakar404/VolC.git
   cd VolC

3. Open the project:

   open -a Xcode VolC.xcodeproj

4. In Xcode, select the VolC scheme and My Mac.

5. If prompted, choose a local signing team under Signing & Capabilities.

6. Press Cmd + R.

VolC runs as a menu bar app, so it will not appear in the Dock. Look for the speaker icon near the clock/Wi-Fi area.

Install as a Local App

You do not need to keep Xcode open after building VolC for yourself.

1. In Xcode, choose Product > Build For > Running.
2. In the Project navigator, expand Products.
3. Right-click VolC.app and choose Show in Finder.
4. Quit any currently running Xcode-launched copy of VolC.
5. Move the built VolC.app into your Applications folder.
6. Open VolC from Applications.

If macOS shows a first-launch warning, right-click VolC.app and choose Open. For a detailed personal build and update workflow, see docs/LOCAL_APP_BUILD.md.

Permissions

VolC may ask for Apple Events automation permission when it controls Spotify, Music, or Chrome. If you denied the prompt, enable it later in:

System Settings > Privacy & Security > Automation

VolC does not capture audio, create an input stream, use AVCapture, or access the microphone. It should not trigger the macOS microphone privacy indicator.

Troubleshooting

• Chrome slider moves but audio does not change

  • Enable Chrome > View > Developer > Allow JavaScript from Apple Events.
  • Make sure the page actually contains a normal HTML audio or video element.
  • Some DRM players, cross-origin frames, and browser UI sounds cannot be controlled this way.

• An app is read-only

  • That app is visible through CoreAudio, but VolC has no public way to set its per-app gain.
  • Add app-specific AppleScript support in AppleScriptVolumeBackend.swift if the app exposes a scriptable volume API.

• No menu bar icon

  • In Xcode, confirm the app is still running.
  • VolC is an accessory app and will not show in the Dock.

• VolC starts twice at login

  • Quit all running copies of VolC.
  • Remove duplicate VolC entries in System Settings > General > Login Items & Extensions.
  • Open the copy in Applications, then toggle Launch at login off and back on.
  • VolC also has a single-instance lock, so a second copy should now exit before creating another menu bar item.

• Xcode App Store page says macOS 26+ is required

  • Download a compatible older Xcode from Apple's developer downloads page instead of the App Store.

Project Structure

VolC.xcodeproj/
VolC/
  VolCApp.swift
  AppDelegate.swift
  Models/
  Services/
  ViewModels/
  Views/
  Resources/
  Info.plist
  VolC.entitlements
docs/
.github/

Development

Efficiency notes:

• Active audio apps are polled every 3 seconds.
• Slider changes are debounced before AppleScript is executed, so dragging a slider does not spam browser automation.
• VolC does not allocate audio buffers or process live audio samples.
• No background worker is kept alive for unsupported/read-only apps.

Quick local checks:

swiftc -typecheck -target arm64-apple-macos13.0 -sdk "$(xcrun --sdk macosx --show-sdk-path)" $(find VolC -name '*.swift')
plutil -lint VolC.xcodeproj/project.pbxproj VolC/Info.plist VolC/VolC.entitlements

For release guidance, see docs/RELEASE.md.

Contributing and Safety

• Contribution guide: docs/CONTRIBUTING.md
• App support policy: docs/APP_SUPPORT_POLICY.md
• Security policy: docs/SECURITY.md
• Code of conduct: docs/CODE_OF_CONDUCT.md

License

MIT. See LICENSE.