There are times when the Firefox responds reluctantly. And it is not only when I have opened many tabs. But there are cases when I have opened as many as 20 tabs and Firefox is working fine and there are cases when I have opened just 5-6 tabs and Firefox behaves lazy.

So, I guess it do not depend on the number of tabs and there must be a specific tab which causes the problem. Isn't there a way to find that tab out and close only that instead of closing Firefox completely1? Is there an addon for that, or a script?

  • 9
    This isn't a duplicate as this asks about CPU and memory (the linked to question just asks about CPU). For CPU go to the page about:performance , for memory go to the page about:memory. Jul 11, 2016 at 10:48

3 Answers 3


The BarTab extension for Firefox (not available for the latest Firefox versions) might be useful for improving the situation:

BarTab can intercept when tabs are loaded in the background or restored after a browser restart and will only load the content when the tab is actually visited. It also allows you to free memory by unloading already loaded tabs, either manually or automatically.

Otherwise, you might switch temporarily to Google Chrome, where Shift + Esc displays the per-tab usage:



Opening the browser to about:memory can show per-tab memory usage.

Further reading


For Firefox, I've made an addon which displays tab memory usage in the corresponding tab's title.

It provides user with tab related stats and memory usage...




  • How many tabs are currently open
  • How many tabs have been opened during this Firefox session
  • How many tabs have been opened since the addon was installed
  • Displays tab memory usage in title
  • Preference to toggle tab memory usage on/off
  • Preference to set interval between memory usage collection
  • 13
    Do you know ANY way to find out even a hint as to which TAB (or even relevant URL) is eating CPU?
    – tbone
    Mar 15, 2015 at 17:54
  • Afraid I don't at the moment, but once I find out I plan on including that data in the addon too.
    – bobbyrne01
    Mar 18, 2015 at 17:56
  • I'll ask since you may have the knowledge....these various addons that "unload" tabs - in my experience, they seem to visually unload them, but Firefox doesn't give up any of that memory; or, when you restart Firefox, it seems to eat all of the memory required for the opened tabs, even before you click on each one and it loads (implying they are being physically loaded in the background, but not displayed). Would you happen to know if this IS in fact the situation?
    – tbone
    Mar 18, 2015 at 20:28
  • 1
    @bobbyrne01 I am using your addon right now! Good stuff.
    – AntonioCS
    Sep 27, 2015 at 21:47
  • 3
    @tbone about:performance shows per-tab CPU usage. Matthew's comment on the main question covers this, but it doesn't show up as a reply here and is waaay underrated.
    – mgjk
    Nov 26, 2016 at 13:52

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