I switched to FireFox when Safari started to have massive problems. Firefox is not much better. Mozilla forum responses keep blaming AddOn incompatability. But mostly I'm running security & privacy enhancers (DoNotTrackMe, Ghostery, etc)

I have a DSL line.

I've got an MBP 2.66 Ghz Core i7, wish I could install more than 8 GB memory. I tried a PCI card, but it causes a kernel panic (Delkin Devices ExpressCard 34 PRO SSD PCI Express)

I want to keep >100 tabs open. Closer to 200. Used to be able to do that with Safari. What has changed ?

FF was working adequately until the last security update. Now its just constantly showing anywhere from 20% to 80+ %CPU usage. It can take many seconds to open a new blank tab, and then 10-20 seconds before it accepts input (trackpad click on the URL box, or keyboard entry).

Seems like every other FF update screws it up.

  • Yes it is FF update screw up, they had that problem before and fixed it but still have it with new one. (36.0.4) With only 6 tabs open, it uses 6% CPU, 600 Meg Ram. (36.0.1)
    – Ruskes
    Mar 21, 2015 at 19:36
  • Just updated to 36.0.4 and it lowers the CPU to 4% and RAM to 400 Mb with same 6 Tabs. Each new Tab adds about 50 MB to RAM.
    – Ruskes
    Mar 21, 2015 at 19:41
  • So with your 200 Tabs open I would worry about RAM usage, that would explain why is it slow. It must be way over 8 Gig and using disk as expansion, if it is SSD maybe ok, but not so with HDD. The high CPU should be only momentary while it is loading the website, if it is constant then a specific web site is responsible.
    – Ruskes
    Mar 21, 2015 at 19:52
  • @OldMac It has nothing to do with Firefox, which is a well designed app. Safari and Google Chrome would be brought to their virtual knees like Firefox when stressed with far, far too many open tabs and a lack of RAM. Mozilla itself recommends that if you keep more than 100 tabs open at the same time, you may need to use a different mechanism to keep track of pages. This document has some great tips about reducing the memory footprint of a running FireFox instance.
    – IconDaemon
    Mar 22, 2015 at 0:24
  • 1
    PS. You will see improvement with a newer operating system, too. Of that I have no doubt.
    – IconDaemon
    Mar 22, 2015 at 1:39

2 Answers 2


The problem seems to be that you want to keep 200 tabs open. Try reducing this number and the computer should perform better.


You could also have web browser addons installed that have memory leaks/eat up memory/cpu. Try disabling addons, and see if you still have the problem. If the problem is resolved by turning off browser addons, you can turn them back on, one by one, until you find out which one/s might be causing it, at which time you can remove/uninstall those specific addons from the browser.

Also, if possible, you should definitely upgrade the amount of RAM in your Mac/Computer. Either way, adding more RAM should help everything run faster/smoother.

Best of luck! Hope this helps :)


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .