Mac Error Message: ‘Can’t open Firefox because a copy of Firefox is already open’

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If you get the error message “Can’t open Firefox because a copy of Firefox is already open” you might think you could Force Quit after entering CMD OPTION ESC on your keyboard. But surprise, Firefox is not listed there (and it doesn’t show with CMD-TAB either).

Here is your next step …

Open the Activity Monitor app in Applications: Utilities

Search “Firefox” (no quotes) while in the Disk tab at the top.

You will see Firefox in the listing below.

Double-click on the listing, and you will see a Window Open with details about the Process Group: Firefox that is running.

Look for the Quit button in the lower left of the small window, and click it.

After a couple seconds Firefox will quit and the Firefox item listing will disappear.

You should be able to Open Firefox, once this ghost Firefox process has quit.

Check it out. Hopefully Firefox opened.

If not, you might have to delete Firefox, and re-install.


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