Firefox Already Running But is Not Responding Error

Firefox Already Running But is Not Responding Error

Mozilla Firefox is one of the most famous and used web browsers across the globe. Your personal settings, bookmarks, and other information are stored in the Firefox profile. Although being quite a famous web browser, it does not mean that it will not shows you any technical error.

One of the annoying and disturbing errors in Firefox is already running but not responding error. Well, if you are also facing this problem and searching for solutions to get this problem resolved, then you are at the right place. This post will provide you with all possible solutions you can follow to resolve the problem.

Windows error

Why Does The Firefox Already Running But Not Responding Error Arises?

The Firefox not responding error mainly arises when a different instance of the Firefox is running in the background. Although, it is not a common error, and solving this error can sometimes be difficult. You need to understand the reasons why this problem occurs so that you can prevent this error arising again in future.

Here is the list of possible reasons behind Firefox does not respond while it’s already running.

  • When Firefox crashes in the middle of a process.
  • The Firefox has been updated, and the new version is not compatible with your PC.
  • When the Firefox application is already working in the background.

How to Fix Firefox Already Running But Not Responding Error?

Now, let’s look at the solutions you can easily follow step by step to fix the Firefox not responding error

Solution 1. End The Pending Firefox Processes

When you have not closed Firefox the last time you used it, the application might run in the background. Now, when the application is running in the background, and suddenly you try to open it again, the Firefox hangs and can lead to this problem. 
To solve the pending Firefox processes, below are the steps you can follow. 

  • First, press the “Windows + E” keys to run Windows Explorer on your PC
  • Then click on the “Processes” tab option. 
  • Now, under the list of pending processes, select the pending processes of Firefox (firefox.exe). 
  • After that, click on the “End Process” option available on the below right side of the task manager window. 
  • Then a new pop-up warning message will be open on your screen.
  • Click on the “Yes” option to finally end the pending process of Firefox.
  • Moving ahead, process the above steps one by one for all the pending processes of Firefox.

Once you have cleared all the processes, try to launch the Firefox browser and check if this method has helped you solve the error or is it still occurring.

Task Manager

Solution 2. Remove the Lock Files in Profile

Below are the steps you can follow to delete the lock files from your PC.

  • First, on your PC press the “Windows + R” keys together to open the windows run command.
  • In the insert box, type “%APPDATA%\Mozilla\Firefox\Profiles\” and hit the enter button.


  • After that, open the “.default” folder.
  • Then, search for the “parent.lock” file and select it.
  • Now, press the “delete” key to get the file deleted.

If you have set up more profiles, then you delete the lock files in each profile by following the same steps.

Solution 3. Permit Rights to the Default Folders

If you have not allowed permission to the default folder, it might lead to the Firefox freezing problem. To get it done, below are the steps you can follow.

  • At first, open the Windows run command by pressing the “Windows + R” keys together.
  • Then in the windows run command, type “%APPDATA%\Mozilla\Firefox\Profiles\” in the insert box and then hit the enter button.
  • Thereon, right-click on the “.default” folder and click on the “Properties” option.
  • Under the General tab, ensure you have unchecked the “Read Only” option. If it is marked, click on the tick box option to uncheck it, and click on the “OK” option.

default page

Solution 4. Run Firefox in the Safe Mode

So, here are the steps for running the Firefox browser in safe mode.

  • First, open the Power shell on your PC.
  • Now, navigate to the default location where the Firefox installation files are saved. The default location is> C:\ Program Files\ Mozilla Firefox\ firefox.exe.
  • After that, type “& ‘C:\ Program Files\ Mozilla Firefox\ firefox.exe’ -safe-mode”.
  • At last, hit the enter button to use the Firefox browser in safe mode.

Solution 5. Reinstall the Firefox Browser

Reinstalling the Firefox browser on your PC can be a solution for fixing the Firefox already running but not responding error. So, for reinstalling Firefox, below are the steps you can follow to get the process done.

  • First, go to the Windows start menu and type “Add or Remove Programs” in the search box.
  • After that, press the enter button on your keyboard.
  • Now, click on the “Apps and Features” option.
  • Under the installed programs list, click on the “Firefox” option.
  • Now, click on the “Uninstall” option.
  • At last, download and install the latest version of the Firefox browser from the website.

Once you have downloaded and reinstalled the Firefox browser, then launch Firefox again and check if the error has been resolved or not.

apps and features

Solution 6. Restart your PC

Last but not least solution for getting the problem resolved is to perform a deep restart of your PC. Performing a deep restart of your PC can help you to clear many errors related to the PC.

  • First of all, close all the background running applications on your PC.
  • Press the “Alt + F4″ keys to open the windows power command.
  • After that, click on the drop-down arrow icon and select the “Restart” option.
  • At last, click on the “OK” option.

Once your PC is restarted, try to open the Firefox browser and check for the presence of the error.

Related Pages: Firefox Cant Load Websites But Other Browsers Can

Wrapping Up:

After following the above mentioned solutions, you can easily resolve the Firefox that is already running but is not responding error. In case, while performing the steps, you face any problem, then you can reach out to us through the chat box, or you can also mail us at ( Our experienced and professional experts are available 24*7 at the help desk to provide the best feasible solution for your query.