Sorry to hear about this issue. Does anything in this article help: Quick fixes if your Firefox slows down?

Some Windows 10 users are encountering severe performance problems with Firefox 57 related to accessibility services. Please see the reply from philipp in the following thread in case this bug is affecting your system: Firefox 57 hangs up.

No. I've updated Firefox. I have everything else updated. Measurements show that I get about 180Mbs download. I have a 4.0GHz i7 with 32GB of RAM.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding

https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix

https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

Please let us know if this solved your issue or if need further assistance.

Pkshadow said

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there? https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix https://support.mozilla.org/en-US/kb/firefox-uses-too-much-memory-ram https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding Please let us know if this solved your issue or if need further assistance.

Starting in Safe Mode makes a big difference! Now I have to track down the add-on that is causing the problems. (It might be BitDefender or something.)

March 2018 I also experienced issues with FireFox Quantum not working on 3 different computers. These were all vintage computers upgraded from windows XP or Windows 8 to windows 10 64-bit envirnoment. Firefox started and it work lockup almost immediately to where it took forever to recongnise that the mouse moved or I could ley into the seatch box. With Firefox 58 I could invoke the task manager by keying in the Alt-Ctrl-Del combination. I then say that Firefox always showed 5 or move sessions running. After researching this I decided that my hardware speed and memory were the problem and running Firefox 64-bit in a single thread was the solution. See http://www.ghacks.net/2016/07/22/multi-process-firefox/

With firefox open key about:config into the firefox search box. Press enter and click the "I accept the risk" button scroll down through the entries until you find the entry(s)

browser.tabs.remote.autostart = true

browser.tabs.remore.autostart.2 = true and change the entries to false by clicking the line(s) with your mouse. browser.tabs.remote.autostart = false browser.tabs.remore.autostart.2 = false

Close FireFox. Reboot and Good Luck. My systems run as fast as 32-bit I am current on Firefox releases.

See https://support.mozilla.org/en-US/questions/1192233 to run a single session Quantum version

I too had the slowness/lockup issues. Have Win 7 64-Bit machine. I tried all the 'fixes' I could find... NOTHING worked for me. Here's what I did to fix it all.

1) I downloaded/installed Google/Chrome. Hate all the spying they do, but I was easily able to import all my sites/passwords/etc from Firefox. 2) I got GC working well, no issues, Ensured 100% working great. 3) I then uninstalled Firefox TOTALLY!! Completely uninstalled Firefox. Then deleted Firefox folders. Then deleted Firefox registry entries. 3a) Instructions on how to completely remove Firefox can be found by doing a simple google search. 4) I then rebooted, downloaded and installed Firefox Quantum. Imported all passwords/bookmarks/etc from GC. 5) Have tested all out, and currently seems to be working.

Crossing fingers, but right now I'm thrilled to have Firefox back!! Hope this 'solution' may help others. If didn't work, I would have just kept GC as my main explorer.

Spoke too soon. Just four days later I'm back to the extreme slowness and locking up issues. I've not updated or installed anything since I got it all working correctly. I've ran spyware/adware programs, I can find nothing wrong. Applied previous 'fixes' that others have posted... complete waste of time.

Unfortunately it's now time for Firefox to leave my system. I'm uninstalling, going back to Google Chrome. I despise all the spying they do, but I need a browser that actually works.

I'll periodically check the boards, if a real solution is ever posted, I'll try again. Best wishes Firefox, was fun while it lasted.

Hi gda63378, if you try Firefox again, compare a private window with a regular window to bypass saved data such as cache, cookies, and local storage. Another diagnostic to rule out extensions and hardware acceleration incompatibility is Firefox's Safe Mode. See: Diagnose Firefox issues using Troubleshoot Mode.

jscher2000 said

Hi gda63378, if you try Firefox again, compare a private window with a regular window to bypass saved data such as cache, cookies, and local storage. Another diagnostic to rule out extensions and hardware acceleration incompatibility is Firefox's Safe Mode. See: Diagnose Firefox issues using Troubleshoot Mode.

I don't think I'll try again until if/when there is another massive update. I spent days trying to resolve this issue before. I had ZERO problems until the update. Then days of trying fixes and such before going to Google Chrome. That's when I completely uninstalled Quantum and re-installed. I thought I had it licked, worked fine for a few days, but then back to the slow as molasses, locking up, etc. I tried all the 'fixes' before, tried again, no change. Safe mode makes no difference. I'm not the only one having this issue, it's not my computer, it's the actual program itself. I loved Firefox, always recommended to my friends. Not I'm stuck with Chrome. Again, don't like the spying they do, but having a browser that works is paramount. You guys have ruined a good browser. Quit blaming the users, not ALL of us lodging complaints have faulty machines.

Hi gda63378, I don't think I've blamed you or your computer.

Firefox is tested with a relatively small group of beta testers, and some bugs and incompatibilities are missed until regular release. Then when users report the problem, it's a matter of chasing down what's going on so it can get fixed. That is often difficult and I understand if you've lost patience.

It's intriguing to think about how a fresh installation could work well for 3 days and then grind to a halt. What changed?! I'm sure you'd like to know, too. This honeymoon period doesn't fit the usual pattern of device driver, security software, or malware issues, and most likely you restarted Firefox and your OS at least a few times during that period. Maybe someone else with the same symptoms will figure it out and share the answer with all of us.

I'll periodically peruse the boards, see if anyone ever posts a solution that seems to work... long-term. Again though, I made zero changes to anything with my system. I've no clue why it worked fine, then stopped. I just know I don't have the time to continually try and figure it out.