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Firefox is Already Running but is Not Responding [Fix]

8 min. read

Updated onOctober 4, 2023

updated onOctober 4, 2023

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Firefox is a robust browser and provides many features to help you get the best out of your surfing experience. Unfortunately, there are times when Firefox is already running but is not responding on Windows.

Here is what you need to know. When you launch the browser, it opens an instance of Firefox where you can surf and do all the work you need. While it runs, you can still launch new Firefox tabs or sessions, which open as a second instance.

There are no limits to the number of instances you can open, but it can take a toll on your PC since each instance occupies a certain amount of memory. Therefore, the more instances you have open, the more PC resources are used up.

If you have so much memory used up by the browser, you may start experiencing some issues, andFirefox may stop responding in Windows 10/11.

What does it mean a copy of Firefox is already open?

When you click on the Firefox icon, it opens the browser so that you can use it for whatever you wish. At this point, the Task Manager registers a new process running on your computer. In some rare cases trying to launch another Firefox triggers an error where your computer tells you Firefox is already open.

This is not a typical experience as Firefox has no limits on how many copies you can run concurrently. For example, in the image below, I have eight instances of the browser running.

A few other errors users have faced using Firefox include:

What can I do if Firefox is running but not responding?

1. Close Firefox and restart the computer

Your computer will function more smoothly if you restart it. A reboot clears the computer’s memory, putting an end to any processes that are using up RAM. Additionally, it’s possible for an app to consume your memory even after you’ve closed it, and a restart makes sure this does not happen.

Lastly, a reboot may also resolve problems with peripherals and hardware.

2. End the browser process

End task is a tool in Windows Task Manager’s Application processes tab that enables you to stop any process that is not responding. When one of your applications is frozen or not responding, you may use End Task to terminate it without restarting your computer.

3. Delete profile lock files

If you can not delete the lock file after an error warning, reboot your computer and delete the file before attempting to re-launch your Firefox browser.

4. Check Firefox access rights

Note that when Read-only is selected, the browser becomes incapable of writing to its folder, resulting in the Firefox error message.

The browser produces system files in a profile folder in the browser’s folder in the C drive to run smoothly. When Firefox loses the needed rights owing to read/write or system file failures, it becomes unable to create any files.

5. Open Firefox in troubleshoot mode

Alternatively, hold down theShiftkey while double-clicking on the Firefox icon.

Starting your browser in safe mode is a great way to troubleshoot when Firefox is already running but is not responding. It disables all the extensions and bad settings.

If the browser works well in safe mode, then you may consider disabling the latest extensions added, as they may be the cause of the problem.

When Firefox is running but not responding in Linux, you can launch it in safe mode using the script below:$ firefox -safe-mode

6. Disable Extensions

7. Uninstall and reinstall Firefox

Note that uninstalling Firefox completely removes all of the browser data, including stored bookmarks. If you wish to save your bookmarks, you should export them and then import them when the reinstallation is complete.

How can I refresh or reset my Firefox browser?

When you refresh or reset Firefox to its default settings, the following elements will be impacted:

Resetting Firefox to its default settings might help if it begins to crash, run slowly, or show intrusive adverts. The reset tool resolves a variety of difficulties by reverting the browser to its original default mode while retaining important data such as active tabs and bookmarks.

There you have it. We hope you have been able to successfully resolve your Firefox issue. Please note that we have not written these solutions in any particular order but we recommend starting with a simple computer reboot.

While it may not be the most efficient solution, it is the easiest and allows the computer to fix its problems when possible.

These steps are mainly specific to issues of Firefox is already running but is not responding, but you would be able to fix moregeneral Firefox issues on Windows 10 & 11in a few steps as well.

Firefox is Already Running but is Not Responding [Fix]#

What does it mean a copy of Firefox is already open?#

What can I do if Firefox is running but not responding?#

1. Close Firefox and restart the computer#

2. End the browser process#

3. Delete profile lock files#

4. Check Firefox access rights#

5. Open Firefox in troubleshoot mode#

6. Disable Extensions#

7. Uninstall and reinstall Firefox#

How can I refresh or reset my Firefox browser?#