Firefox is Already Running Error Message

A common error message that is encountered when using Firefox is:

“Firefox is already running but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system.”

This error message will appear when a Firefox is initially being started, and it can be caused by a number of different reasons, including:

• Firefox did not shut down properly the last time it was used,
• The Firefox profile folder cannot be found or accessed by Firefox, and
• There is an issue with access rights available for Firefox.

Each of these issues can cause the Firefox is already running error to be displayed when a new instance of Firefox is attempted to be launched. Unfortunately, the error message is always the same, so there is no way of knowing which issue is causing the problem. As such, each fix will have to be worked through until the error is corrected. Profiles and access rights will be addressed in the future.

Using Task Manager to Close Firefox

If Firefox did not close properly the last time you used it, you can either restart your system or use Windows Task Manager to correct the problem.

In most cases, when you open Task Manager (Ctrl+Alt+Del), you will not see an instance of Firefox running in the Applications tab. Instead, you will have to go to the Processes tab and close Firefox from there. Scroll down through the processes until you find firefox.exe. Click it to highlight it and then click the End Process button. Do this for all entries you find.

You should now be able to start Firefox normally.

Restarting Windows to Close Firefox

In some cases, even though you closed Firefox, it may still be running in the background (due to an error on closing). You can close all background applications by shutting down and restarting your system. If it is running in the background, you may receive an error when the computer is trying to close asking if you want to shut down the program.

When your computer starts up again, you should be able to start Firefox as normal.