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Can't open or close Firefox; already uninstalled, reinstalled, created new profile, deleted parent lock, etc. tried everything; many reboots, etc. what's left?!

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  • Last reply by cor-el

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Hi, I hope someone can help! I've tried everything.

I’m using a desktop; Dell; newer. Windows 10; 1903; plenty of speed and space left. No viruses, etc.; have done many scans (malwarebytes, adware, etc.)

For whatever reason (I think I incorrectly shut down Firefox and/or my computer, and that was the beginning of the problem), Firefox is causing lot of issues.

Won’t open or close. followed all the advice on this site.

Found out on this site to try ending Firefox in task manager; when that didn’t work; went in to and deleted parent.lock from the profile.

Then rebooted the computer; still wouldn’t open (or did once, but then had the same problem?) Tried shutting off the computer and restarting rather than rebooting many times during all this process as well.

I followed what someone said about adding the word OLD after places.sqlite. So in the original profile folder I have:


that didn’t help things. Then someone said to add OLD to ‘prefs.js’

So I have:

                  Etc….up to # 9; I have 9 of them

That didn’t help.

I then saved that original profile to the desktop. Uninstalled Firefox; and reinstalled it.

If you go into profile folder, it shows the original profile(‘default’) and a new one I guess it creates when you reinstall Firefox? (called ’default-release’).

I tried opening etc. with that new ‘default-release’ profile. Same issues. Again I went into task manager, to end process (sometimes works for some of the instances; but usually not all?); deleted parent.lock again. Rebooted.

Then I created a brand new profile (without going into Firefox; but following some instructions on how to create a new profile without Firefox being open).

I opened Firefox with that brand new profile (it asks me which of the 3 profiles I want to use when I went to open Firefox). I opened tabs, used it, etc. works ok; …..

BUT it won’t close or reopen! So same issues with the brand new profile!

The ‘default-release’ profile and the brand new one I created were never changed or touched; never added the word OLD to anything in there; made no changes.

So Firefox wouldn’t close; so I had to do all of the above again (try to end task in task manager; delete parent.lock, and reboot).

So now I’m at my wits end!!!

I can’t find anything left to try.  : (

I hope someone can help!


All Replies (20)

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This might be resolved by performing a Clean reinstall. This means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.

To do a clean reinstall of Firefox, please follow these steps: Note: You might want to print these steps or view them in another browser.

  1. Download the latest Desktop version of Firefox from (or choose the download for your operating system and language from this page) and save the setup file to your computer.
  2. After the download finishes, close all Firefox windows (or open the Firefox menu New Fx Menu and click the close button Close 29).
  3. Delete the Firefox installation folder, which is located in one of these locations, by default:
    • Windows: (Note: Check both folders.)
      • C:\Program Files\Mozilla Firefox
      • C:\Program Files (x86)\Mozilla Firefox
    • Mac: Delete Firefox from the Applications folder.
    • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
  4. Now, go ahead and reinstall Firefox:
    1. Double-click the downloaded installation file and go through the steps of the installation wizard.
    2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.

Please report back to say if this helped you!

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Thanks so much for replying!

Before I follow the instructions above, I have some questions so I don't screw anything up!

1. the instructions don't say anything about rebooting anywhere or in between any steps. Should I be rebooting anywhere during that process?

2. The instructions also say don't us a 3rd party uninstaller. When I uninstall, I always go to programs and features; right click; uninstall; that's what we should always be doing, right? But the instructions don't say anything about uninstalling anything. Should I be trying to uninstall the Firefox on my computer first?

3. The download above at, your first link, the default one, is that 32 bit or 64 bit? I used that download; But my computer is 64 bit; and I’m guessing the default install is 32 bit? Does that matter?

4. Should I use that other link above and specifically choose 64 bit? Are there issues more with one than the other? Can a 64 bit machine use either?

5. Should I delete the parent.lock on any of the 3 profiles I have now in Firefox? (because Firefox isn’t closing as it should be again); so isn’t Firefox in some kind of ‘lock status’?

6. Does it matter that in the original profile file I added the word “old” to those files I mentioned? Should I leave that as it is?

7. There are a LOT of files/folders in c:\program files\mozilla firefox. I should delete them ALL?

8. In c:\programs files (x86)\mozilla firefox I have only 2 things: a ‘defaults’ folder (10/23/19) and a CFG file (?) kl_config_62fbb8f7…..etc…… does that make sense?

9. Does it matter that in the task manager, services: “mozilla maintenance” says stopped under status. Should it be say stopped?

Thanks! I just don’t want to mess this up.....

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I didn't hear back, so I went ahead and not only did all of the above but installed Firefox completely first; rebooted; did all this; and I can't believe this!! I opened it after installation. closed it; got some crash report. rebooted and now I can't open it again.

how is this possible!?

I put on my desktop (before deleting every mozilla file in my computer), a copy of the original and 2nd profile.

but that wouldn't be a problem, right?

I hope someone really high up or knowedgable can help or I won't be able to use Firefox  : (


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by the way, in the new profiles folder (from the new installation), I see 2 profiles:

ncf6lw8s.default (inside that is one thing only! time.json file)


a default-release one as well which looks like it has a bunch of normal stuff?

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Firefox 67 first started creating a default-release profile. This is normal these days.

Q1: What happens when you try to start Firefox?

For example:

  • Error message
  • Taskbar icon, no window
  • No visible evidence of live, but firefox.exe appears in the Task Manager
  • Something else

Q2: Any difference if you try Firefox's Safe Mode?

In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

  • "3-bar" menu button > "?" Help button > Restart with Add-ons Disabled
  • (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?

Q3: Can you share the crash report ID?

There's more info on that in this article: Firefox crashes - asking for support.

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What security software do you have?

It is possible that your firewall or other security software blocks or restricts Firefox without informing you, possibly after detecting changes (update) to the Firefox application. Remove all rules for Firefox from the permissions list in the firewall and let your firewall ask again for permission to get full, unrestricted, access for Firefox and the plugin-container process and the updater process.


Try a clean reinstall of the current Firefox release and delete the Firefox program folder before installing a fresh copy of the current Firefox release.

If possible uninstall your current Firefox version to cleanup the Windows Registry and settings in security software.

  • do NOT remove "personal data" when you uninstall the current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including personal data in profiles created by other Firefox versions

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

  • (64-bit Firefox) "C:\Program Files\Mozilla Firefox\"
  • (32-bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\"
  • it is important to delete the Firefox program folder to remove all the files and make sure there are no problems with files that were leftover after uninstalling

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

If you keep having problems then you can create a new profile to test if your current profile is causing the problem.

Reinstall Firefox

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As you can see, I’ve tried everything. I’m not a tekkie; and I’m overwhelmed and extremely discouraged with all this; and it’s ALL I’ve done for about a week now. I’m soo frustrated that I can’t just uninstall and reinstall this!

Anyway to respond to your prior posts (I spent all day on this): Yes, I see that this ‘default-release’ thing is the profile that’s created when it creates a 2nd profile.

When I try to start Firefox, nothing happens! No error message, nothing.

Most of the time (always last week?) I have to end Firefox by end task in task manager. Then I usually have to go into %appdata%\mozilla\firefox, etc. and delete the parent. lock (from what I’ve learned); then reboot and then it will usually start in safe mode if I want. Once in a while it will start in regular mode once or twice after that; but not always; but it will usually start in regular mode. (not always)

Once when I got in safe mode, I could see there were no extensions, etc. There were/are 3 ‘default’ plugins that seem to get created when you do a fresh installation? (shockwave something, widevine something and something else).

I started in safe mode by holding down shift key and the Firefox icon; hope that was ok. You describe something different? Another way to restart in safe mode?

I will send that crash report thing after this email if I can figure it out I guess.

I have Kaspersky total security (20.0.14) which I’ve used for years and have had a problem. I did pause it during some of this troubleshooting, so it doesn’t appear to be the problem; and it has never been a problem before.

I also have Malwarebytes premium (which has always worked just fine alongside my Kaspersky and everything else).

And I run adwcleaner once in a while.

I don’t know what you mean “remove all rules for firefox from the permissions list in the firewall”.

I did a clean reinstall (as someone in another thread suggested that). (after about the first 7 hours of trying 100 other things as previously described in my prior postings)!

I deleted all the firefox programs folders, etc. BEFORE installing the fresh copy. I was then able to open Firefox maybe 1-2 times I think? But if you close it, eventually you ran into the same problem. It would just not open; and I would have to close in task manager; delete parent.lock; reboot and try to open again. But usually I can’t reopen it regularly after that.

I did use the firefox installer and choose 64 bit when I did the fresh clean reinstall.

Before I deleted firefox completely and deleted everything from all the profile folders, etc., and everything in %appdata%\mozilla\firefox, etc…..I did put a copy of the profiles on my desktop. I put: one of the original profile. One of the default-release one and one of the one I created myself that I was told to try doing.

I also have a saved folder on my desktop with the bookmarks as far as I can tell.

I did remove these 2 files as well before fresh clean reinstall • 64-bit Firefox) "C:\Program Files\Mozilla Firefox\" • (32-bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\" As you suggested (as someone suggested) before. 100%.

I don’t remember (when I uninstalled firefox) getting something asking me about removing ‘personal data’; but if I did I would have removed it anyway, I just wanted EVERYTHING related to Firefox off my computer!

Since I did the fresh clean reinstall I have noticed this error message though: BUT I don’t even know if it’s related to firefox?? Crash Reporter box: The application had a problem and crashed. Unfortunately the crash reporter is unable to submit a report for this crash. Details: Couldn’t re the application data file.

I have diligently followed EVERY suggestion. I seriously have nothing left to try that I can think of. I can’t think of a step I missed?

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I forgot to say:

I do get when trying to open in regular or safe mode:

Firefox is already running, but is not responding. the old firefox process must be closed to open a new window. that's when I end task; delete parent.lock; reboot (sometimes 1-2x) THEN I can sometimes reopen 1-2 times in reg or safe mode.

then it all starts over again.

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update: I'm still working on doing the report to submit. I'm working on opening Firefox in safe mode to do this.

I had to end task; reboot; THEN go to %appdata%\mozilla\firefox\profiles, etc. to delete parent.lock.

BUT you can only delete that AFTER ending task AND REBOOTING. then delete it. then reboot AGAIN.

Then, and only then, can you try to reopen Firefox.

this is the same cycle for many days.

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ok; I finally just got it opened in safe mode! I will try to leave it open until I hear back.

i did about:crashes and it says: "no crash reports have been submitted"!! how is that possible?

so then I see it says you can enter this in run box: %APPDATA%\Mozilla\Firefox\Crash Reports\submitted I did that; and clicked enter and got:

Windows cannot find C:\Users\myname\AppData\Roaming\Mozilla\Firefox\Crash. Make sure you typed the name correctly, and then try again.

HUH?? I typed it exactly as above in bold. I tried it 3 times.

I then physically when to my pc, clicked on users, etc...all the way to "LastCrash"; tried to open it. It said how do you want to open it. I chose notepad. it says: 1572827898

in the "installtime20191030021342" file it also has the same numbers.

in the events folder there is nothing.

what should I do?!

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FirefoxHelpPlease said

ok; I finally just got it opened in safe mode! I will try to leave it open until I hear back.

Yes, I suggest never exiting Firefox again, if possible. ;-)

%APPDATA%\Mozilla\Firefox\Crash Reports\submitted
I did that; and clicked enter and got:
Windows cannot find C:\Users\myname\AppData\Roaming\Mozilla\Firefox\Crash. Make sure you typed the name correctly, and then try again.

Hmm, seems to cut off at the space? Could you start in


and see whether Crash Reports even exists yet.

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I really do appreciate any help anyone can give me! (even though I'm so frustrated with all this...).

so please let me know what I can do next to help anyone who's helping me : )


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sorry; I just saw you posted something just before I did.

I don't know what you mean "seems to cut off at the space"?

I went to: %APPDATA%\Mozilla\Firefox as you suggested and in there is a Crash Reports folder.

when I open that I see 3 things:

1. events folder 2. InstallTime file 3. LastCrash file

"LastCrash"; tried to open it. It said how do you want to open it. I chose notepad. it says: 1572827898

in the "installtime20191030021342" file it also has the same numbers.

in the events folder there is nothing.

what should I do?! thanks

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Hi FirefoxHelpPlease, since you do not have either of these folders there

  • pending
  • submitting

then I don't think Firefox has recorded the crashes. Makes sense considering you mentioned:

FirefoxHelpPlease said

The application had a problem and crashed.
Unfortunately the crash reporter is unable to submit a report for this crash.
Details: Couldn’t re the application data file.

I don't know why your Firefox won't shut down when it is meant to shut down (and continues to run in memory). When did this problem start?

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oh dear; I'm starting to really worry noone can fix this : (

Has that ever happened before that someone as high up as you (top 10 and 8737 solutions) cant' fix something?

If not, does Firefox (or can you report to someone) have an engineer or someone that takes over after the forums?

I would say it started no later than October 26 (not sure if it was 25, 24, 23?).

I only know it was around then because of an email I sent to someone and I referenced it.

So I've been working nonstop on this for over a week!


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1. Restart your computer 2. Clear your cookies and cache 3. Restart Firefox in Safe Mode 4. Reinstall Firefox 5. Refresh Firefox 6. Create a new Firefox profile

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Hi FirefoxHelpPlease, would you like to try "downgrading" to the Extended Support Release of Firefox 68? This release was designed for company use to create feature stability for a long period of time, interrupted only by security updates. Individuals also can use it if they like. This article has more info:

Switch to Firefox Extended Support Release (ESR) for personal use

If the problem is a new incompatibility with Firefox 70, that might be the best workaround. Usually Firefox will object to using a profile that has been used in a higher version, so after installation, you'll need to create a new profile. However, you then may be able to switch profiles using the about:profiles screen -- we can come back to that.

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Senali: I don't mean to be disrespectful, but if you read ANYthing in this thread at all you'd realize that all that was done and a whole lot MORE, like 30 hours worth more!

Jscher: you're a huge help! yes! I will try anything. I'm not sure I understand what that all means, but sure!

Yes, this Firefox we've been talking about is all version 70.

So how do I begin with version 68? Do I uninstall Firefox 70 and remove particular files after the uninstall? or do anything special first? What do I do first; my brain is completely fried with all I've done so far. And is there someone I can talk to on the phone that can walk me through all this? Even if it's a paid service? or you?

And should I keep those folder on my desktop that have all the files from my original profiles, including 'bookmarkbackups, extensions, minidumps, sessionstore-backups, and a whole bunch of other stuff.

By the way my original profile info is in a folder on the desktop also. And I notice that under 'crashes' there are 3 things: 1. events folder: empty 2. store.json.mozlz4 3. store.json.mozlz4.tmp

does that help? thanks!!

And I went up to click yes on all the boxes for you, but why does nothing happen when you click 'yes'; nothing appears to happen? Did you get all the yesses?

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Hi FirefoxHelpPlease, when you use the "full" installer, you can choose to create a new program folder for FirefoxESR alongside the regular Mozilla Firefox program folder so you can experiment without disturbing Firefox 70 (other than probably it will change your default browser at the Windows level).

Full installers can be downloaded from this page (scroll down to your preferred language):

Look for a choice to customize the folder somewhere along the way in the installer.

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In that link you sent me, what is Windows MSI? Do I do the 'windows' or the 'windows MSI' one?

And what is a 'full installer'?

And are you saying I should choose the customization option? But why, what would I customize? What would I choose to customize?


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