Please consider turning on send info to Mozilla before posting a question. This helps us help you. As I have no info from your system that would help see things that cause issues. Things that could be turned on that I would've seen with info.

See if Multi-Processor Support is turned on. Multi-processor support feature may be disabled depending on your setup (it was for me) - you can check this by launching Firefox, then enter in "about:support" in the address bar; near the bottom, you should see a heading that says: "Multiprocess Windows", then look at the value next to it. If it says "0/1", then that means it's disabled. and/or will say enabled or disabled also if has 0/2 and higher.

Look in Task Manager and see how many instances of Firefox icon is running.

You can open the about:config (copy/paste into address bar) page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

You can try to modify multi-process settings to see if this has effect.

set dom.ipc.processCount to 1 if it is currently set to a higher value (4) disable multi-process windows in Firefox

You can disable multi-process windows in Firefox by setting these prefs to falseon the about:config page.

browser.tabs.remote.autostart = false browser.tabs.remote.autostart.2 = false

You may be part of a Mozilla experiment, called 'Shield Studies'. Without even knowing it, you may have volunteered for this Mozilla experiment. Would you go to : Options => Privacy & Security => under 'Data Collection and Use' : Did you uncheck : 'Allow Firefox to install and run studies ' or is it checked  ?

To check if you are enrolled in these studies : Type in the address bar about:studies

Any extensions that you see listed there, you can either disable or remove, such as Safe Browsing version 4 (at the end of the experiment they will be disabled anyway). See for further information : https://support.mozilla.org/en-US/kb/shield

Note : Firefox 57 Quantum release date Nov 14th https://www.mozilla.org/en-US/firefox/quantum/ Note : Legacy Extensions will be disabled and or removed.

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

thank you for the reply pkshadow...but

yes, multi process window is set to 0/1 (disabled by ad-ons)

in about:config, i do not have multi process window listed

Ok...

Ok.

What about in the equivalent to Windows Task Manager. What is going on there with ram usage ? What program is using most and how much ? As well number of Firefox Icons or anything related to Firefox ?

Have you had this a long time ? Do you keep intakes clean for the fan and blow out the book. Are the fans working ? Can you control the speed setting RPM of the fans ? If so maybe boost them until this is solved.

What about video card air intakes and blades etc ? Can you adjust RPM ?

You could always uninstall and reinstall using a Full Version Installer https://www.mozilla.org/firefox/all/

Or Note : Firefox 57 Quantum release date Nov 14th https://www.mozilla.org/en-US/firefox/quantum/ Note : Legacy Extensions will be disabled and or removed.

memory usage (8gb installed) - kernel 656 mb - firefox 457 mb - supportmozilla.org 107 mb

cpu usage % - kernel 656 - firefox 457

one firefox icon

i've had this problem for about a year

6 moths ago i installed an ssd and cleaned out the inside while i was there

i have smcfancontrol 2.6 and always on high (5999 rpm) with firefox

i've reinstalled firefox a few times with same result

how do i change multi process from 0/1 to 1/1? i have no ad-ons but it states that multi process is disabled by ad-ons.

such a shame because i like firefox but safari is my default for now.

Not sure which Extension/add-on is disabling multiprocessor as said send info not turned on and nothing sent. I would have known.

Please look at your extension page and check for Legacy ones. I would say those would be the ones to turn off 1 at a time to see after restarting Firefox which one it is. Norton is one that can disable it.

Also the Gear icon right top beside the search bar in extensions has a pull down, Check for Updates.

Multiprocessor may or may not improve your ram issue. Note for next time, nothing less than 16gig if not 24gig.

i have zero ad-ons and my one extension disabled.

are you telling me that i need 16-24 gigs or ram for firefox? i have 8. https://www.mozilla.org/en-US/firefox/56.0.2/system-requirements/

safari is my default browser for now, maybe for good...

os 10.12.6 firefox 56.0.2 (64bit) 8 gb ram