My Mac sometimes ends in a state with high CPU usage for SystemUIServer. This causes poor performance and decreased battery life.

I can resolve the problem by rebooting the machine but the problem inevitably reappears after some time.

I have found out that this seems to be caused by an application that has an icon in the menu bar. I tried closing all such applications by right-clicking them and selecting their Quit menu item. Now, I notice a gap in the menu line and when I hover the mouse cursor over the gap then I see the infamous spinning beach ball of death.

Screen shot of menu bar icons

How do I identify the misbehaving the underlying application – i.e. its name and/or filesystem path?

I am running Mac OS X Lion version 10.7.5

  • You have incorrectly uninstalled a app. The menu bar icon (space) is still there but not active that is why you get the spinning ball. Best solution reinstall the app and uninstall correctly.
    – Ruskes
    Aug 30, 2014 at 20:21
  • Check in System > Library > CoreServices > Menu Extras
    – Ruskes
    Aug 30, 2014 at 21:56

3 Answers 3


Use the Accessibility Inspector, accessible from Xcode → Open Developer Tool → Accessibility Inspector.

Click "Show" on the "Hierarchy" sub-section (which will show you the Application Name).

Click on the "Target Icon" at the top of the Inspector (Labeled: Start inspection follows point).

Hover over the item and the pane may show you enough information for you to determine what it is. For example, hovering the Dropbox menu bar item shows "Dropbox <version>" under AXHelp, and hovering Little Snitch shows "Little Snitch Agent" under AXTitle.

  • Great suggestion and exactly what I was looking for. Unfortunately the Accessibility Inspector does not update its information when hovering or clicking the hung application area in the menu bar.
    – mgd
    Aug 31, 2014 at 7:07
  • This worked PERFECTLY! I had been seeing a suspicious-looking icon in the menu bar for many months now. It had strange drop-down options that made it seem like it was malware of some sort. I tried this suggestion and, voila, mystery solved — it was Telegram's menu bar icon. That explains why Telegram kept quitting on me: whenever I saw that suspicious menu bar icon I would activate it and select "Quit," which told Telegram to quit. Thank you for this beautiful hack.
    – Aquarelle
    Jul 31, 2019 at 21:48
  • Worked like a charm. It was TechTool Pro for me. Which hadn't hung, so wasn't obvious in Activity Monitor.
    – ttt
    May 21, 2022 at 7:34

You can look in Activity Monitor's list of processes for any which are not responding. Such processes are shown in red, as below, and can be force quit or killed.

  • I tried this, but no processes are red (not responding).
    – mgd
    Aug 31, 2014 at 7:01

Try opening a terminal window and entering killall SystemUIServer and press enter, this should reload your menu bar.

You can also try copyingcom.apple.systemuiserver.plist from ~/Library/Preferences to your desktop, then deleting it from the Preferences folder. This will force a new .plist to be created.

You may just want to run this handy command from terminal:

 cp ~/Library/Preferences/com.apple.systemuiserver.plist ~/Desktop/com.apple.systemuiserver.plist ; rm ~/Library/Preferences/com.apple.systemuiserver.plist ; echo 'All done here. Restart your computer from the Apple Menu'

It will reboot your computer after copying the file to the desktop and removing the specified file.

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