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"Firefox is already running but is not responding" error message - How to fix it

All of your personal settings, bookmarks, and other information are kept in your Firefox profile. Firefox needs an unlocked profile to start up, and if the profile is locked, it displays the message, Firefox is already running, but is not respondingA copy of Firefox is already open. This article explains what to do if you see this message and how to prevent it from showing at startup.

Note: If this is a recurring problem, see Firefox hangs when you quit it for possible causes and solutions.

FirefoxAlreadyOpen-Mac

Fx34already-running-Win7 Firefox Already Running - Win1 Firefox Already Running - Win1

End Firefox processes

If Firefox did not shut down normally when you last used it, Firefox might still be running in the background, even though it is not visible.

If you try to open it while it's running, an error message will appear with the option to click Close Firefox. If that doesn't solve the problem, restart your computer or try the following options. Restart your computer to see if the problem goes away or try the following options.

Restart your computer to see if the problem goes away or try the following options.

Ubuntu Linux

  1. Click on System and choose Administration.
  2. In Administration, click on System Monitor. Here you will find firefox-bin one or more times.
  3. Highlight the listing and click End Process for each one.

Use the Windows Task Manager to close the existing Firefox process

  1. Right-click on an empty spot in the Windows task bar and select Task Manager (or press Ctrl+Shift+Esc).
  2. When the Windows Task Manager opens, select the Processes tab.

    Task Manager
  3. Select the entry for firefox.exe (press F on the keyboard to find it) and click End Process.
  4. Click Yes in the "Task Manager Warning" dialog that appears.
  5. Repeat the above steps to end any additional firefox.exe process, if more than one entry is found, then exit the Windows Task Manager.
  6. Start Firefox normally.

Initialize the connection to a file share

If you store the profile on a file share, try accessing the file share beforehand using Windows Explorer.

Check access rights

Firefox must also have the right to create files in the profile folder. The error can occur if you try to use a profile from a file system mounted with read-only permission (e.g. a remote Windows share which doesn't have "Allow network users to change my files" checked).

To check if the profile folder has the proper permissions:

  1. Go to your Firefox profile folder - see Finding your profile without opening Firefox.
  2. Go up one folder.
  3. Right-click on your profile folder and select Properties.
  4. Click on the General tab.
  5. Make sure Read-only is not checked marked.

    readonlyprofile.png
  1. Go to your Firefox profile folder - see Finding your profile without opening Firefox.
  2. Go up one folder.
  3. Hold down the Ctrl key while you click on your profile folder, and select Get Info.
  4. Make sure Ownership & Permissions is set to Read & Write.
  1. Go to your Firefox profile folder - see Finding your profile without opening Firefox.
  2. Go up one folder.
  3. Right-click on your profile folder and select Properties.
  4. Click on the Permissions tab.
  5. Make sure Folder access is set to Create and delete files.

Restore data from a locked profile

If you are unable to unlock the profile using the above methods, use the Profile Manager to create a new profile and migrate your data from the locked profile to the new profile. For information on how to do this, see Recovering important data from an old profile.




Based on information from Profile in use (mozillaZine KB)

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Comments

See /forums/knowledge-base-articles/704725 for related discussions about this thread.

There's been some positive activity in bug 278860 (seee the latest comments by Michael Kaply) that leads me to think that the error message might be changed soon .... in which case we'll need to update this article.

trlkly

And it now has been changed, meaning that entire section needs to be put in another article about the new error message.

trlkly

We may want to keep the information here for users of Firefox ESR, though, since it won't change for them until Firefox 17.

Actually this was changed in Firefox 14. The error message for a missing profile is "Your Firefox profile cannot be loaded. It may be missing or inaccessible."

We should remove this section from the article and create a new article for the new message if we see people asking this question.

Michael Verdi said

Actually this was changed in Firefox 14. The error message for a missing profile is "Your Firefox profile cannot be loaded. It may be missing or inaccessible." We should remove this section from the article and create a new article for the new message if we see people asking this question.

For the record, a new article was approved last August, that covers the new error message:

How to run Firefox when your profile is missing or inaccessible

P.S. The "Check the profile name and location" section was already removed for Firefox 14 and above back on Dec 4, 2012, in revision 34315.

From the Firefox 34.0 Beta release notes:

New | Recover from a locked Firefox process in the "Firefox is already running" dialog on Windows

Here's the related bug:

  • Bug 286355 - Need win32 implementation of nsIProfileUnlocker

I see that Joni approved a revision on Oct 31 2014 to update this article for Windows. Joni also created a "Needs change" entry (Needs technical check and proofreading before RFL) to review this article before it's localized.

Joni, Should we mention what to do if you see a "Profile is missing" error? Related bug:

  • Bug 1068657 - Sometimes "Profile Missing" dialog appears after closing the Firefox process in the "Firefox already running" dialog

I have a revision pending in the How to run Firefox when your profile is missing or inaccessible article. ... and Joni approved it :-)

Related discussion:

P.S. Some details copied from bug 1068657

7. When the "Firefox already running" dialog appears, quickly click on the <Close Firefox> button.
Expected results: 
"Firefox already running" dialog is dismissed, the firefox task is closed after a few seconds, and Firefox is automatically restarted.
Actual results:
Sometimes the "Profile Missing" dialog appears. After dismissing the dialog, Firefox does NOT restart automatically. After the initial process is finally killed (automatically after several seconds), then you can manually start Firefox again. See http://www.screencast.com/t/d8cXT4J3AMKZ 
Notes:
- the issue is a follow up from bug 286355 which introduced the new "Firefox already running" dialog with the option to Close Firefox if the task is still running.

Something else I found:

The new dialog box and "Close Firefox" button isn't available on Windows XP. See https://bugzilla.mozilla.org/show_bug.cgi?id=286355#c53 The article needs to be revised to change the {for fx34}{for win} tags to {for win7, win8}.

I made a new revision based on the fact that the new Firefox 34 "Firefox is already running" dialog for Windows doesn't apply to Windows XP. I also added a new fx34 screenshot for win7, win8 to replace the other one that was a bit fuzzy. I let the old screenshot show for Windows XP.

(After thinking about it, we don't need to mention the possible "Profile Missing" error in this article. We already say what to do if clicking the "Close Firefox" button doesn't solve the problem and besides, the error might only happen very rarely. I couldn't get it to happen no matter how quickly I pressed the "Close Firefox" button on Firefox 34 Beta 7.)

This came up in another discussion: https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding/discuss/6033 Firefox hangs on exit: "already running" message may vary

I just updated http://kb.mozillazine.org/Profile_in_use to include the following possible error messages, based on http://mxr.mozilla.org/mozilla-release/source/toolkit/locales/en-US/chrome/mozapps/profile/profileSe...

  • (On Mac OS) A copy of Firefox is already open. Only one copy of Firefox can be open at a time.
  • (On Mac OS) A copy of Firefox is already open. The running copy of Firefox will quit in order to open this one.
  • 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. <snip>
  • Firefox is already running, but is not responding. The old Firefox process must be closed to open a new window.

Shouldn't this article be revised to mention the Mac OS error?

Also, the current article title doesn't apply to Mac OS: "Firefox is already running but is not responding" error message - How to fix it

Should the article title also be revised to include the Mac OS error? I was thinking maybe: Firefox is "already running" or "already open" error message - How to fix

AliceWyman said


Shouldn't this article be revised to mention the Mac OS error?

Also, the current article title doesn't apply to Mac OS: "Firefox is already running but is not responding" error message - How to fix it

Should the article title also be revised to include the Mac OS error? I was thinking maybe: Firefox is "already running" or "already open" error message - How to fix

Correct. Agree.

Thanks. I'll wait a few days to see what others think and then change the title of this article to Firefox is "already running" or "already open" error message - How to fix

I googled the Mac error and found this old screenshot and uploaded it. I'll add it to the article for mac.

FirefoxAlreadyOpen-Mac

[[Image:FirefoxAlreadyOpen-Mac]]

That message seems relatively current: A copy of Firefox is already open. Only one copy of Firefox can be open at a time. /questions/1020199

P.S. I also made an edit to the search summary, to change it to:

How to start Firefox if you see an error message, "Firefox is already running, but is not responding" or, on Mac OS X,  "A copy of Firefox is already open".

Hello :-)

I tried in several ways, but I can't get the Italian image for Mac. Can you help me?

Thanks in advance
Michele

Hello Michele :-)

you can't see the image in the article at all ?

The usual way to get the Close Firefox "already running" error is by closing Firefox and then immediately reopening it. That works for me in Firefox 36 on Windows 7. I couldn't get the "Close Firefox" message to appear on Mac Os X 10.6.8 though, so I ended up doing a google image search.

By the way, is it worth updating the Firefox 36 Windows 7 "Close Firefox" image? See this image I just captured, by closing and then quickly reopening Firefox 36.0.4: [[Image:Fx36alreadyrunning-Win7]]

Fx36alreadyrunning-Win7

Compare that to the Firefox 34 Win7 image being used in this article (the Close Firefox and Cancel buttons are reversed): [[Image:Fx34already-running-Win7]]

Fx34already-running-Win7

Hello Ideato :-)
I can see the image, but I can't get the "Close Firefox" message to appear and then capture the Italian screenshot.

Thanks Alice :-)
I already tried to do a google image search, but there are no Italian images of the message for Mac :-(

Also in my xp i have an exclamation mark and NOT a question mark !

Fx36alreadyrunning-Winxp

Image:Fx36alreadyrunning-Winxp

Maybe we should just leave the existing screenshots?

I don't even know how big of an issue this error is any longer. The new shutdownhang crashes in version 36 that the Firefox 36 release notes mention (related bug) probably prevent many of these "already running" errors that are caused by hangs at shutdown.

AliceWyman said

Maybe we should just leave the existing screenshots?

Agree.

it appears, that the section that reads:

Remove the profile lock file If restarting the computer or ending the Firefox processes didn't help, it may be that Firefox previously exited without deleting the lock file.

... is no longer reflecting the status quo. for quite a while now the parent.lock file always remains in the profile for instrumentation purposes like crash detection or reset prompts that get triggered when you open firefox with a profile that wasn't in use for the last 60 days (for example see MattN's comments in https://bugzilla.mozilla.org/show_bug.cgi?id=726759).

while a third party process having that file in use will maybe still trigger the warning and it may be beneficial to try and remove it for troubleshooting purposes, we shouldn't give the impression that the presence of parent.lock is unwanted or a sign of a problem...

You're right, this article needs updating. I'll add it to the "Needs change" list.

I see from these bugs that this change took place in Firefox 13: Bug 766316 - parent.lock is not deleted

Bug 294260 - Safe Mode: Auto detect previous start-up failure and offer to start in safe mode

A new revision adds a section for the MOZ_NEW_INSTANCE environment variable.

Does anyone have any reference links for this solution? How common is this? I only found one instance of MOZ_NEW_INSTANCE in the support forum from 2 years ago, and in that case, the variable wasn't set.

I've PMed the editor to post in this thread as well.

martin__1343578

Hi Chris,

This is probably a rare case, but that was mine, and I could not find this solution on the web. I thought that giving this alternative here would be the most visible for the other users using Google like me, and would have a maximum impact.

--Martin

What are the instructions on modifying the start script?