Activity Monitor will display all the currently-active processes that include this search term.In the ‘Search’ bar, enter the name of the application that’s been causing you problems, such as ‘Safari’ or ‘Preview.’.Make sure the Activity Monitor’s ‘CPU’ tab is selected.Open a Finder window and navigate to ‘Applications > Utilities > Activity Monitor.’.If the application doesn’t appear in the ‘Force Quit’ menu, then it’s time to dig a bit deeper and kill the process (or processes) that are associated with this application: Relaunch the app to see whether this easy fix has solved your problem.If the misbehaving app appears in this list, then select it and click ‘Force Quit.’ The subsequent popup displays a list of all the apps that are currently running on your Mac.

Click the ‘Apple’ logo in your Mac’s menu bar.Your Mac can only force quit apps that it detects as being open, so misbehaving applications won’t always appear in the ‘Force Quit’ menu, but since this is the easiest method it’s always worth a shot:

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