[Fix] Firefox is Already Running But is Not Responding Error Message

If you are getting any of following error messages when you try to launch Mozilla Firefox web browser in your computer, you have come to the right place:

or

I receive the above mentioned error message frequently whenever I close Firefox and re-open it. Many times Firefox becomes very slow or I face problems while adding/removing bookmarks, in such case I restart Firefox by closing and re-opening it and I get this error message at startup. Sometimes Firefox requires restart to install and apply new updates, in such case this error message also appears.

Actually this error message appears if Firefox process firefox.exe is still running in background and was not terminated/killed by operating system automatically. So when you try to launch Firefox, it detects that an existing process is already running in background and throws the above mentioned error message.

Following are some solutions which you can follow if you get “Firefox is already running, but is not responding” error message while opening Firefox web browser:

1. Click on “Close Firefox” Button

The error message dialog box contains 2 buttons: Close Firefox and Cancel. Click on “Close Firefox” button and it should kill the already running Firefox process and should also start a new Firefox process. It’ll open a fresh window of Firefox without any error message.

2. Have Some Patience and Wait

If clicking on “Close Firefox” button doesn’t work, then have some patience. As they always say “Patience is a virtue“. So wait for some time and Windows or other operating system such as Linux, Mac may automatically kill existing running Firefox process. Once the already running Firefox process is terminated, a new window of Firefox will launch without any error message.

3. Manually Kill Firefox Process

If your OS doesn’t kill Firefox process, you’ll need to manually kill existing Firefox process. Following steps will help you in terminating Firefox process:

1. Press Ctrl+Shift+Esc keys together to open Task Manager.

2. Now go to Processes or Details tab.

3. Right-click on Firefox.exe process and select End task or End process tree option. You can also click on “End task” button given at the bottom in Task Manager window.

That’s it. It’ll forcefully kill Firefox process. Now try to open Firefox again and it’ll start a new Firefox window without any error message.

PS: Linux users may use killall firefox-bin and killall firefox commands in Terminal to kill Firefox process.

4. Restart Computer

If nothing helps, restart your computer and it’ll kill all running processes which are causing this issue. After reboot, open Firefox and it’ll start without any problem.

5. Reset Firefox Web Browser

If you receive this error message frequently and sometimes Firefox web browser opens for you, you can try to reset it to fix the problem permanently. It’s the 100% working solution. You can reset Firefox to default factory settings and it’ll make Firefox brand new in your computer system.

Following tutorial will help you in learning how to reset Mozilla Firefox web browser:

[Tip] How to Reset / Restore Your Web Browser Settings to Default Factory State

Once you reset Firefox, it’ll fix all problems and error messages related to Firefox browser.