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Firefox 30 won't start, hangs after closing (Bug1004476)

  • 55 replies
  • 120 have this problem
  • Last reply by John99

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Hello, everyone!

I've filed a bug report here: The problem is that after installing Firefox 29 with no profile at all and installing any addon that requires a browser restart (NoScript for e.g.) Firefox restarts OK, but after closing it and trying to open again I get a message: "Firefox is already running". I can see in the Task Manager that there is already Firefox running in the background. I've found several people complaining about this issue. Here: And here:

Thank you in advance

Modified May 13, 2014 11:01:46 PM BST by John99

2nd Update. (Comment by a moderator)
Engineers are working on issues that have been identified.
The known issues are problems with Firefox hanging on closedown resulting in Firefox not restarting unless the hung process is killed.

Workaround ensure Firefox is NOT set to clear History on Close down
Use NewButton New Fx Menu → Preferences → |Privacy| Firefox will: [Remember History v ]
See also my post downthread /questions/997918?page=2#answer-572501 ~J99

 Modified June 5, 2014 12:26:07 AM BST by John99

3rd Update

A fix is now on the Beta Channel Fx30b8 hopefully in a couple of weeks that will be on everyone's Release of Firefox30.

Modified by John99

Chosen solution

Strange, but I cannot reproduce this isssue anymore. Maybe there was something wrong with my profile when I accidentally reproduced it under Firefox 30. I dunno. Really strange.

Well, if it doesn't affect anybody else I think it's time to close this thread.

Read this answer in context 👍 0

All Replies (20)

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Sorry not reproducing this. My STR not working to reproduce.

I am wasting time on a problem few people seem to experience or to have an interest in.

I have other things to do besides Firefox, and when on Sumo I don't want to spend all my time on an issue where even the reporters of the problem do not have time to work out STR.

I did see some hangs but maybe it was a bad nightly, a bad profile or overloading my system. After all I should be able to reproduce on the Release - that is where everyone is seeing and reporting the problem, and presumably on Firefox Release for Window as well as Ubuntu's Canonical not just the Mozillazine 64bit Linux FX29 Release.

We really need help from the guys that see this problem to get proper STR.

IMHO STR that are described from

  • Using a new clean profile.
  • All Plugins disabled.
  • Starting in Firefox's safe mode.
  • (edit - additional note Use only about:blank have no other tabs open. )
  • Trying to exit into safe mode, by using the safe mode restart option,
    New Fx Menu -> Help-29 ->restart with addons disabled...
    Does that hang ?
  • Exiting using the new closedown button
    - that should hang as the test for this.
    New Fx Menu -> Help-29 -> close 29~J99

Of course if you cannot do the above and make firefox hang then you have a workaround that solves your problem.

  • Compare that to your ordinary install and ordinary profile, what are the differences ?
  • Write STR, others will try to reproduce.

Also if you turn on the telemetry reporting the data of slow startups and hangs is anonymised and collected, engineers would have seen a spike for Fx29 and jumped on that.

The Explorer.

Thanks for reporting this hang. I will continue to watch the bug report and some of these threads to see if anyone else is able to reproduce this reliably.

Modified by John99

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Ok, as you wish. But it is still an issue. I really have no time investigating upon this. I rolled back to 24.5.0 ESR. I need a working browser at work. I'm leaving all my efforts to the community (sooner or later you will face this issue yourself again). Just one more thing - people on Mozillazine forum asked me to post a link here with the same complaints:

Good luck, Mozilla!

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Yes I have already noticed that. I also noticed conversely not many comments about NoScript and all has an increase mostly negative over that period. (spike)

Anyone at Mozillazine able to reproduce ?
If so maybe they would like to post in your bug with STR & confirmation.

Currently we are wondering if the changes with netpredictions.sqlite may relate to this problem. (See /questions/998449 & Bug 966469 )

So you could try if setting network.seer.enabled to false helps?

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I also came across on this issue, after stable, fully working 28.0, autoupdate really made things horrible. Using task manager to close/be able to start Mozilla Firefox is insane thing to do! Seriously as far I noticed over web, ppl are replacing Firefox with alternatives cause that issue is really annoying - I am still hoping for any fix that you may release.

Setting: network.seer.enabled to false didnt changed anything at all. Tested it with and without addictional modules (Im using Classic Theme Restorer, avast! Online Security (disabled), Nagios Checker (disabled), NoScript (disabled).

If you need me to provide any addictional informations, feel free to ask.

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Yep, I've been already asked about that by philipp on the previous page here. This option doesn't change anything.

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Yes, sorry I had forgotten about that reply. I see you have tried it. We don't really know yet whether many of these cases have the same cause or not.

I don't think we have any Steps To Reprodue for this yet. I will look around to update myself on what has been going on and post back again later.

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John99 I dont think i have any steps to reproduce it either. It just happend after autoupdate. I additionaly installed Classic Theme Restorer to bring back lost addons bar functionality, but even when I disable it nothing changes.

Hope you will find a way to fix this issue. I will try to visit this post from time to time, if anything you want us to test, just write at channel.

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There is one change being included in a Firefox point update within a few days to potentially help some with this solution, but that is only the same as the seer pref change so it will not help those that have already tried that.

Did you read the info above about STR trying that may either give you a workaround or STR.

This link explains the importance of STR

I also note someone at least partially reproduced this issue testing with a gmail account open and logged in. So it may help to try getting STR by testing

  • one tab, and only one tab open and logged in to gmail. ( Or one tab of whatever you have open and logged in when seeing this as a problem. )
  • Compare that with using Firefox with only blank about:blank page open.
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I've disabled 'network.seer.enabled' and even deleted netpredictions.sqlite file in my profile folder. Doesn't change anything unfortunately. The only fix for now is to disable 'Clear history when Firefox closes' option in the Settings if it is enabled. Then everything is OK.

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Sounds like progress.

 The only fix for now is to disable 'Clear history when Firefox closes' option in the Settings if it is enabled. Then everything is OK. 

Good so you effectively may have STR that are testable. Could you write that up please starting from an empty profile, and only about:blank etc If you need to include something that you login to perhaps trial with a few sites, gmail for one, because there is a possibility the issue is seen there. Try to pick sites people may already have an account with. What about this forum, Bugzilla, and what about Mozillazine as testsites ?

If others can reproduce this bug can be confirmed. If it effectively locks people out of Firefox it is going to be dealt with as a priority, although now it is going to miss the Chemspill point Release.

I have tried to reproduce this and I am sure others have but we obviously miss something. What about the others that you mention complain of this issue; that you are in contact with. Are any of them able to help reproduce this. If for instance it is seen on a Mozillazine forum I would expect them to be able to put formal STR in their forum & directly in your bug if they are able to reproduce this.

Tagged this thread as Firefx29 and escalate so that HelpDesk staff and any developers still around potentially get a chance to see it.

Modified by John99

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Which items have a checkmark in the "Clear history when Firefox closes" settings?

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The default ones - only History section is being cleared, no Data.

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Tried it again and reproduced successfully. What I did:

1) deleted my profile completely 2) started FF 3) Preferences -> Privacy -> Use custom settings -> 'untick' Remember search and form history and 'tick' Clear history when FF closes. 4) close FF and start again - seems to be OK 5) go to about:config and set 'browser.cache.disk.enable' to false 6) close FF and try start it again...

Well, that's how I reproduce it in WinXP and Linux.

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Someone please change the topic to "Firefox hangs after closing"... It has nothing to do with addons as it turned out to be. Any admins here?


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OK I will change title from

  • Firefox hangs after installing addons (Bug 1004476 )


  • Firefox 29 won't start, hangs after closing (Bug1004476)
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Hi, Thank you for supporting this and thank you for all the collaboration. This is indeed the correct bug and there have been some comments today that see that one has resolved this by changing the privacy settings.

Also, as it looks like this is dependent of another issues, [see dependency of bug] they may be looking to fix this in the beta version. Please use the work around in the meantime as the issue is continued to be investigated.

Modified by guigs

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Looks like Firefox's shutdown problems are not limited to Fx29. Apparently Fx misbehaves in a few ways from before Fx28 and continues to have problems into Fx32.

The op has known for a while that the settings affect this and has mentioned that upthread and #c8 in the bug.

Not necessarily good current summary or a full str and I note Bug1004476 may be considered dupe of Bug 9709323, but that in turn is a dupe of a later Bug 1005487 and is in turn being linked with

  • Bug 985655 - [AsyncShutdown] Ensure that Sqlite.jsm doesn't shutdown before its clients

That however is tracking Fx 30,31 & 32

Which bug with a Beta fix are you referring to?

Also, as it looks like this is dependent of another issues, [see dependency of bug] they may be looking to fix this in the beta version. 

You will realise better than me there are quite a few bugs on related issues of hangs at present. Some of which date from before Fx28.

Not directly related but note the last bug mentioned above above: Bug 985655 blocks a reopened bug

  • Bug 917883 - Use AsyncShutdown instead of spinning the event loop in healthreport.jsm

That bug is something I came across for another reason. So along with the seer / netpredictions.sqlite issue* and this thread's bug it seems there are a lot of issues with Firefox close down at present.

*  1005958– Disable seer until new backend is rewritten  - patch ready, lower risk workaround for shutdown hangs in bug 966469
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There are now STR for this or a similar problem that have been verified, and I think the current related bug is where work is in progress is probably

And this bug that has a patch being worked on and tracked for Beta Fx30

Modified by John99

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Using FF 29.0.1 on OS X Mavericks. This problem began with the update to FF 29. Firefox would intermittently hang on closing and I would have to Force Close it either by right clicking and forcing or via Activity Monitor. I tried every other corrective suggestion in this thread - nothing solved the problem. I finally unchecked the "Clear History When Firefox Closes" and FF has not had a hang problem since.

I use some add-ons which clear the History, delete all the cookies including LSO super cookies upon closing, so there is a current workaround which still keeps everything cleaned when I close the browser.

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Note one potential fix is now in the very recent Firefox Beta 30b8 Initial reports suggest this fixes the issue. (Bug1005487#c38) If you have been suffering from this problem and want a fix now instead of in a few weeks time you may wish to download and install the Beta version of Firefox.

The beta version is effectively a release candidate but is only intended for advanced users or testers. I would be interested to hear feedback from those of you that do test this out.

Beta version download

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