Use "Firefox/File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") to close Firefox if you are currently doing that by clicking the close X on the title bar.

See also:

• "Hang at exit": http://kb.mozillazine.org/Firefox_hangs
• "Firefox hangs when you quit it": https://support.mozilla.org/kb/Firefox+hangs

You can check for problems with the places.sqlite database file in the Firefox Profile Folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

Try updating your AVG safe search software that may help. Or try disabling it entirely as Firefox itself provides some degree of protection from phishing and attack sites:

• see http://www.mozilla.org/en-US/firefox/phishing-protection/

Disabling AVG safe search does not mean you need to disable all other security features.

I had the same problem. It only began after updating to 16.0.1

However, I cleared the Firefox cache and the problem disappeared!

Well, in an update it worked for about 5 minutes but it is doing it again. I have reset my browser and then cleared the cache again but still it keeps doing it.

NOTE this chosen solution may not work for everyone, this may not be a fx 16 problem
_{comment by a forum moderator -J99}

It seems to be something unique to 16.0.1.

 I tried all the usual things, rebooting, uninstalling and downloading 16.0.1 and even resetting Firefox to its defaults, but all to no avail.  It just kept freezing and saying 'Not Responding' for about 30 seconds, happening so often as to make the browser effectively unusable.

Finally, I uninstalled 16.0.1 and replaced it with beta 17.0

That's done the trick, and now it's working absolutely fine.

Seems that there's a bug in 16.0.1 that Mozilla need to fix. Was the update from 16.0. to 16.0.1 rushed out a bit too soon?

That has worked now, I installed it and tested with everything I normally do and where it normally did it's not responding thing, it doesn't anymore. So the 17.0 version is the better option

Mozilla seem to be losing the plot. In the past, people expected Microsoft to release software which contained security problems and then re-release it, only for it not to work properly. Now it appears Mozilla is taking over that role! And the solution to this? Install a Beta version, a version still under development!

I suspect that the very great majority of software users look for stability, for a program which works well and meets their immediate needs and which will continue to do so for some time - certainly months rather than, as it appears, days, before a new, "improved" version is developed. Maybe Mozilla should think along these lines; meanhwile, I'm going back to the latest 15 release.

I thought clearing the cache had solved the problem - but it hadn't. If Mozilla wants its users to move to other browsers in droves, this is the way to do it.

Is there a way to download earlier versions of Firefox?

In the meantime I've downloaded the Firefox 17.0 beta. If that doesn't work I will switch to another browser.

Yes, go here:

_{edit inapropriate link removed, please use official links}

• see Install an older version of Firefox
  that does provide direct links to earlier versions including fx 15

I've re-installed release 15.0.1 and found things fine. (When I first ran Firefox after re-installing, I was warned that it was out-of-date.) The large video file I had tried to upload without success under 16, uploaded quickly and with no problems.

Since re-installing version15.0.1, Firefox has automatically downloaded an 8.5mb update which will be installed when I next restart Firefox. I hope this is only an update to 15.0.1 and not 16.

I actually think using a Beta version of Firefox can be a good option. The beta version is pretty stable, and has a great advantage that it has a safe and secure downgrade path to the Release if something is a problem. It is however something newbies should probably not try.

If more users would try the Beta version that gives Firefox more realworld testing, and increases the likelihood of problems being reported and fixed prior to Release.

I am not sure this sort of problem has been reported as a difference between Firefox 16 Release and Firefox 17 Beta. I imagine it will turn out to only affect some subset of Windows users. (It could of course merly be a sessionstore problem and cor-el suggeted a solution for that in the first post above so try that first ! )

If you would like to help get to the bottom of this problem two things could be tried.

1. Try Firefox 16 in a new clean additional profile (If you take care it will not affect any current profile )
   1. Back up your current profile, put the files and folders somewhere safe, outside firefox paths (windows Desktop will do as a location) This is always a good general, and it will help if mistakes are made, or you need the original profile restored quickly after making changes.
      For full instructions see Back up and restore information in Firefox profiles
   2. create a new additional profile. I suggest using only an empty folder as the location in which this is created, and that you do not delete or rename a profile once it is created, fx16R-2012 may be a short descriptive name that is suitable.
   • if this works report back,and lets see if we can discover what it was in your profile that caused the problem
2. Install and try both versions on the same machine and ensuring fx16 is a clean install This is considered advanced, but is something that has instructions that you should be able to understand.
   • Make sure you have backed up your original profile the one with important bookmarks and passwords.
     This time we are to delete the Fx16 program files Not the profile files, and then reinstall Fx16.
     Both Fx16 and Fx17 must have separate profiles available for use. If Fx17 is working and has a Default profile leave that profile only for Fx17 use.
   1. Make sure you have a copy of the Firefox installer for Fx16. Obtain if necessary from http://www.mozilla.org/en-US/firefox/all.html
   2. Uninstall firefox following the instructions in Uninstall Firefox from your computer. You will remove the program files in (32-bit Windows) C:\Program Files\Mozilla Firefox ; or (64-bit Windows) C:\Program Files (x86)\Mozilla Firefox . But not the profile/user data
   3. install Fx16 and use a custom location if necessary. Then create a new profile for Fx16 use (if not already done in step 1 above). You will need separate shortcuts for Fx16 & Fx17 (or use the run commands) and you must start them with profile manager or a shortcut specifying the profile.
   • with both versions on the same machine it ought to be able to sort out the cause of the problem (It would not surprise me to find it turns out to be a profile problem) IF you get this far consider leaving both versions installed, you will henceforth have Beta and Release channels installed and may easily choose the version of Firefox to run. Both channels will in due course update to the newer versions of firefox as they become available

Some other useful links

• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox
• http://kb.mozillazine.org/Testing_pre-release_versions#Installing_multiple_versions
• (no-remote) is only needed IF you run two versions at the same time
  http://kb.mozillazine.org/Command_line_arguments
  but the use of profile manager or a specific profile is essential

I must say I tend to forget how much effort needs to be made to run multiple copies of Firefox.

Recent versions of Firefox do by default automatically and silently update

Since re-installing version15.0.1, Firefox has automatically downloaded an 8.5mb update which will be installed when I next restart Firefox. I hope this is only an update to 15.0.1 and not 16. 

You should first of all consider the risks of using an old outdated version of Firefox that is not secure. Also remember that downgrading usually is not an effective solution, there are usually more effective methods of fixing problems.

If an update has downloaded, you may be able to prevent it by finding and deleting the files see

• http://kb.mozillazine.org/Software_Update#Software_Update_not_working_properly
  from which you will note closing firefox and finding and deleting active-update.xml and updates.xml should reset an update.
  • or the archived Delete update configuration files

To prevent an update if for instance you need an old Version of Firefox for test purposes; one method is to delete the URL in a pref app.update.url . That should prevent that version of Firefox finding upgrades. (Until you open it with the wrong profile !)

1. Navigate to about:config by typing that into the address bar, hitting return,and accepting any warning,
2. type app.update into the search/filter in order to find the entry app.update.url right click on it and remove the value that is in the URL string

• see http://kb.mozillazine.org/About:config

What you write I find worrying. So when Firefox first updated by default automatically and silently from 15 to 16 on my system, it was a version with a security problem which it updated to, which sounds rather more of a risk than me downgrading to 15, which has been available for some time without a hidden security risk. The next silent update installs a version of 16 without a security risk, but one which keeps hanging. And this is progress?

Glad it is not just me!!

Tried everything I can think of to get rid of this extremely frustrating problem. Used firefox for years but so fed up with this that I am seriously thinking about using another browser. Will try to find this 17 Beta then go elsewhere if this does not work.

Come on Mozilla/Firefox get this sorted pronto!!

I think the ideal is to keep everyone updated and to have an up-to-date Firefox that works.

If you have problems with the current Firefox and have crash reporting and telemetry turned on the engineers should be able to see any problems that arise.

Many problems are not related to the Firefox version, but to some other problem with a particular setup.

If you want Firefox Beta visit:

• http://www.mozilla.org/en-US/firefox/channel/

I tried all kinds of recommended fixes and actions to no avail. Finally after 3 months of nothing but grief I got rid of Firefox. Problem solved.

I started having the "not responding" issue with 17.0.1. I tried Beta 18. something and got the same issue. I completely deleted my previous profile folder and started a new install. Same thing. Clicked on Help > About and Firefox updated to 18.0 Went to foxnews.com..............(Not Responding) Now Firefox and IE9 work very much the same

Moving to Chrome.

Hi bdbengtsson,

If I understand correctly you are having problems with both Firefox and iE9, but not with a new install of chrome.

if you wished to continue with Firefox it would probably be best to ask your own question. It could be something as simple as cookies and cache needing clearing. Or a deeper problem affecting both browsers, maybe malware.

Good luck with using Chrome

John99, My problem is with Firefox on my work computer. My home computer seems to work fine with Firefox.

I don't use IE The only reason I mentioned IE9 is because just the other day I had to move my father-in-law from IE9 to Chrome because IE9 has a similar "not responding" issue.

I don't see how my work computer could have a "simple" problem with Firefox as I uninstalled, removed my profile folder and re-installed from scratch only to get the same problem.

I've been using Firefox for years and much prefer it over Chrome but I can't put anymore time into trying to debug Firefox.