Please consider turning on send info to Mozilla from with in Firefox before posting a question. This helps us help you. I have no info from your system that would help see things that cause issues. So I have no info.

Please scan with these tools as they are not anti-virus and that is what you scanned with only. Please use more than 1 scanner as each uses diff tech :

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware

Save your Report and google each before deleting anything as do not want to delete something you need, If need help :

• https://forums.malwarebytes.com/topic/9573-im-infected-what-do-i-do-now/

Post in only 1 forum, then wait.

FIREFOX TO SLOW 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

If still issues 7mins for below.

Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 59.0.1 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

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

Hello again, This problem does not seem to disappear. I have uninstalled and reinstalled to no avail. I have scanned with multiple antimalware programs, including avast, housecall, malwarebytes, microsoft safety scanner, nothing to be found. The problem seems to pop up after a while only. Rebooting my PC helps for half a day, then the issue starts again. This is getting extremely annoying... How can I find out what is causing this? Is there a way - log files maybe - to see what is going on while the pages are loading so slow?

HI you have not said if you have tried Safe Mode : SAFE MODE

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

In Firefox Safe mode these changes are effective:

• all extensions are disabled (about:addons)
• default theme is used (no persona)
• userChrome.css and userContent.css are ignored (chrome folder)
• default toolbar layout is used (file: localstore-safe.rdf)
• Javascript JIT compilers are disabled (prefs: javascript.options.*jit)
• hardware acceleration is disabled (Options > Advanced > General)
• plugins are not affected
• preferences are not affected

TEST''''is issue still there ?

You have not mentioned your connection or speed that you should have. Try testing your speed in a other browser besides Firefox http://www.speedtest.net/ If not getting the speed you are suppose to contact your ISP.

Can check what is going in and out : https://fileforum.betanews.com/detail/LiveTcpUdpWatch/1523303038/1

Also every camera, every what ever you have not turned off in Win10 Settings panel is contacting the internet. Please go through every setting and disable everything you do not need or want. You can always turn them on when need to. You can also uninstall everything that will allow you to with a right click that MS has stuffed into Settings and the Start Button (uninstall from both places) Uninstall Maps and turn it off. Use Microsoft Disk Cleanup then run it again and remove System Files as this takes ram and space, weekly. Defrag monthly.

• https://support.microsoft.com/en-ca/help/4002019/windows-10-improve-pc-performance
• https://www.tenforums.com/tutorials/26120-optimize-performance-windows-10-a.html

I would guess that with 12 gig of ram your on a older machine.

Please Go to the 3 Bar Menu then Options --> General --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 1 = No Multiprocessor = slow again. Try 2 Restart Firefox after making these changes please. Note : Hardware Acceleration is for Video Card, Monitor to see if remain off or to turn back on.

Please Search for Device Manager and see if Microsoft has switched your Video Card Drivers out for their own. This can cause slowness if the have. If they have then they have switched other things out also. You may need to go to the maker of your Video Card ( no info here as said ) and get your drivers back. https://www.howtogeek.com/302595/how-to-stop-windows-10-from-automatically-updating-hardware-drivers/

Hi,

To be clear: the problem only exists in FF and only when the machine has been running for a day or so. It disappeares after a reboot but comes back after a while. At this moment FF runs fine again, but the problem will probably pop up somewhere during the day.

• Yes I did try safe mode on numerous occasions.
• Connection speed: 94.79 Mbps
• The problem is not in other software that is connecting to the internet: chrome works fine,
• I ran ccleaner and disk cleanup without success.
• Machine is about 4 years old: i7-4790, 3.6Ghz octacore processor
• Performance only shows recommended settings, when unticking this I can only see a hardware acceleration option. I have tried this before, but will try again when the problem comes back.
• video card is a GeForce GTX 1050 Ti with proper NVidia drivers, Am updating to the latest drivers right now, will see if this changes anything.

I will check what happens with the network traffic when the problem exists again. I already checked with wireshark but could not see anything out of the ordinary. Will try with licetcpudpwatch (best program name ever btw).

The problem persists. Every day Firefox goes limp and only a reboot will fix it. The traffic shows nothing. No changes are being seen in livetcpudpwatch when the problem occurs, Traffic stalls then. I am getting very frustrated. Any more ideas on a possible cause and/or solution?

Eureka! I have uninstalled avast antivirus (disabling it did not do anything). This seems to have improved the issue a lot. So far I have been able to surf the web for 2 days straight with no apparent problems (although maybe now my PC is infected with every virus out there :D). Hopefully this will be the definite answer to the issue.