Written for Synergy 3 (v3.7.2) and Synergy 1 (v1.21.4), checked 3 October 2026.
Operating system: macOS
If macOS says it can't update Synergy 1 or Synergy 3 because the app is in use, quit it from its menu bar icon, then run the update again. Closing the window isn't enough: the app keeps running in the background.
How to fix it
- Click the app's icon in the menu bar at the top of your screen.
- Quit the app:
- Synergy 3: choose Exit.
- Synergy 1: choose Quit.
- Run the update again.
If the message still appears, restart the Mac and run the update before opening the app again.
Closing processes
If restarting doesn't clear it, open Activity Monitor (Applications, then Utilities, then Activity Monitor), search for synergy, and quit every process it finds. Or run this in Terminal:
pkill -i synergy
Synergy 3's background service can start again by itself after being force quit. If it does, quit the app from its menu bar icon as above, or remove the app as below.
Removing the .app
If that doesn't help either, remove the app from Terminal. Open Terminal (Applications, then Utilities, then Terminal) and run:
sudo rm -rf /Applications/Synergy.app/
This removes the app you see in the Applications folder. Once its processes have stopped or the app has been removed, continue with the update.