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Why does Firefox always slow, & freeze?

  • 15 uphendule
  • 33 zinale nkinga
  • Igcine ukuphendulwa ngu John99

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I've tried resetting and various other workarounds I've seen on the forums, and still, FF will soon jump to using up 4 Gigs of RAM, and when I want to open a new window, or tab, it will freeze, and I must wait till the spinning ball does it thing, watching the CPU usage shoot up to 300 or 400%, or in some cases, as high as 2,000%!! All the while showing "Firefox is not responding". Then, it will finally go back down (CPU usage, not RAM), and function for awhile, or it may crash. Once it gets up that high, I will reboot the program, but it doesn't take it very long to climb right back up there. What else could be the issue?

All Replies (15)

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Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that turns off some settings and disables most add-ons (extensions and themes).

(If you're using an added theme, switch to the Default theme.)

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu by clicking on the Restart with Add-ons Disabled... menu item:

If Firefox is not running, you can start Firefox in Safe Mode as follows:

  • On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
  • On Mac: Hold the option key while starting Firefox.
  • On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
    (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

Once you get the pop-up, just select "'Start in Safe Mode" Safe Mode Fx 15 - Win

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

Thank you.

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I don't know if these work on Mac, but;


Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

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Malware scanners for Windows won't work on a Mac.

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

If the new profile works then you can transfer some files from an existing profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem.

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Thanks, I'll try it... One question:, if I open in Safe Mode, will I still be able to restore my previous session?

Speaking of which, do you have any idea why, when opening a previous session, the pages/tabs aren't shown in the history, as they are in other browsers? I hate to clear past history, for that may also eliminate any record of the tabs I currently have open. And I can't even simply copy all the urls, and paste them to a list, since they are not shown in the history, how else can I do this?

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i ll trying to solve ur problem so wait 4 my reply

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StevenCee; Open your FULL History. At the top of the page you should see a button Import and Export. You can use this to make a copy of your history / bookmarks if you want.
Safe mode turns off all extensions and turns off some of your settings temporarily..

cor-el; Are there mal-ware scanners for Mac's? And Linx?

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I don't want bookmarks of everything in my history. I want some way to either bookmark all the tabs currently open, or find out if deleting my history, will mean when I re-open FF, will it be impossible to restore my previous session. and if so, how are we supposed to clear history ever, if it means losing everything we have open, when it restarts? Other browsers, when you open the tabs/windows that were open when you exited, will show them at the top of the history, so you could delete everything else up to the present moment.

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You can open the history in the sidebar (View > Sidebar) and sort by visited date if you want to remove recently visited web page.
You can use Shift plus cursor down to select multiple items.
You can also consider to use Private Browsing mode.

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Sorting by visited date won't help, because I'd have to somehow know the date I first opened every tab currently open. With other browsers, when you first open them, and then hit "open previous session", all those tabs/windows show up in the history, so then it's easy to simply delete everything below/previous to those, simple. With Firefox, not, I'm holding on to way too much history, for fear of losing forever all my currently opened tabs & windows.

My other question, which could solve this issue, but not yet addressed by anyone, is how FF finds the tabs I've got open, and re-opens them, when I close & then re-open FF. If I close and delete all my history, will FF lose it's means to re-open my previous session?

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Can anyone explain the method FF uses in restoring previous sessions? If I delete my history will that also eliminate any reference to my tabs & windows, making it impossible to re-open the session?

I see I have a "sessionstore.js" file, so is that where all currently opened pages are stored, and not in the History? Also, I have a second "sessionstore" file, same size, but it is a ".bak" file, and seems created by a music editing program, as it calls this file a "Harmony/Melody score". Why is this file always in my FF folder, the program needed to open the file, is not open and running, so I can't figure out how it's being created, and it is a copy of my sessionstore.js file, this is very perplexing... And I noticed I also have a "sessionstore.bak-20140127194636" file showing a creation date of 2/5/14.

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u update ur firefox browser version otherwise u reset ur browser

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Go to the Mozilla Add-ons Web Page (There’s a lot of good stuff here) and check these out;

Extension Defender :: Add-ons for Firefox

Send Tab URLs

There may be others so poke around.

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Gaurav: I've reset it, and I'm using the most recent version of FF...

FredMcD: I can see the Defender add-on helping with malware, etc., but the Tab URLs will only copy the tabs in each window, requiring me to manually got through every window. I wonder why FF doesn't simply list the newly re-opened tabs/windows in the History, as other browsers do, making copying them, as well as clearing all the history up to the present, a snap.

I still would like to know, if anyone knows, whether deleting past history will also delete the capability to re-open the tabs I currently have open.

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I don't think deleting history should not interfere with anything else. There should be a setting for that. Firefox Options > Privacy.

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Firefox may create <strike>sessionstore.bat</strike> sessionstore.bak files. I do not know anything about Mac.s and OS-X but I am guessing it is just miss identifying the file type because many other Apps will create .bak files.

Firefox does not need the History to reopen your open tabs. However if you clear all your history you do clear the history of those open tabs.

Note the backup option from the History / Bookmarks library only backsup the bookmarks (backup as .json or export as .html) it does NOT backup the History. If you wish to backup the History you need to backup the database file places.sqlite or the whole Firefox profile

To save open tabs that you do not otherwise have a record of bookmark them. Note if you right click on a tab you get an option Bookmark All Tabs That bookmarks all the open tabs and puts them all in the same folder.

Okulungisiwe ngu cor-el