Determine which tab in Firefox is using CPU resources?

firefox cpu-usage browser-tabs resource-usage

115,908

Solution 1

Resource usage can be monitored via the about:performance page which goes as Task Manager since Firefox 64. It had a major overhaul and now gives much more detailed insight into the performance of tabs and add-ons.

Solution 2

about:memory shows Firefox's memory usage details. There's also a button on that page that allows you to minimize memory usage.

Solution 3

The first likely culprit is Flash. Kill Flash - now.

Then it may be rogue Javascript code. Firefox's Javascript Deobfuscator extention lets you watch the count of Javascript function calls :

It is not a measure of CPU usage, but a close enough proxy : find the function with a runwaway number of calls and you will likely have caught the culprit.

Solution 4

Firefox 16 should introduce proper built-in profiler at last.

Solution 5

By using Flashblock and Nevercrash, now replaced with FlashStopper and UnloadTab you go a long way into blocking Flash or tabs, preventing CPU waste instead of tracking it. This holds, but less, for memory too. Flash, e.g. Youtube is prevented to start until you click on them, so you may launch them in several tabs and they wait for you to open the tabs. Tabs are uloaded from memory and idle until you reopen them and they are refreshed from the cache (if still available).
Shutting down the Internet for a while also works during the time you don't need it ;-)
Firefox fragments virtual memory so much that it's using an excessive amount of real memory (there is too much unused virtual memory in real memory). One needs to periodically stop and restart Firefox with the same pages. That will defragment its memory and the whole system will run faster by reducing the swapping.
On my Ubuntu system, real memory usage slowly climbs up to 98%. Then it's time to stop Firefox and restart it: it will then use less than 1MB of real memory instead of 3MB. The same holds for Thunderbird..

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115,908

chris

Updated on September 17, 2022

Comments

chris almost 2 years

Is there anything in the current Firefox similar to the Task Manager in Google Chrome? (Shift + Esc)

There is something that occasionally takes up enough CPU to make Firefox unresponsive - but with multiple windows, each with a dozen or so tabs open, trial & error is going to take a while.
- Admin over 13 years
  
  No, there is no way to natively do this. I won't post an answer though because there might be some third-party solution.
- Admin over 13 years
  
  I found this via google, it's a plugin. addons.mozilla.org/en-US/firefox/addon/bartab ...Makes it so (supposedly) the tab doesn't use resources until you click on it and are actively viewing it. From the user comments it may not work exactly as advertised, and apparently in firefox4 this is native behavior without the plugin. Personally I'd try ff4 if you aren't already.
- Admin almost 13 years
  
  Firefox doesn’t use separate processes for each tab and plugin like Chrome does, so it has no reason to have a task-manager like Chrome’s.
- Admin over 12 years
  
  @chris: Ah right, they switched to a faster release model somewhere this year...
- Admin almost 9 years
  
  @Synetech, there may be no need for a process viewer, but for exactly the reason in the question there is very much a need for whatever you'd call a task manager that deals with memory and CPU usage at the tab level. As of mid 2015, there is still no tab resource viewer, but there is a project called Electrolysis which is splitting Firefox into (initially) two processes (for content and UI respectively) followed by further sub-divisions presumably to follow the Chrome model, at least loosely.
- Admin almost 9 years
  
  as of August 2015, these two extensions show Memory usage of the tab: tabSizeTooltip and Tab Memory Usage (while Memory's not CPU it's a strong indication as quoted by Kal and Peterflyn). Also Multi-process is coming soon to stable Firefox it's called "Electrolysis" alias "E10s" reddit thread.
- Admin over 8 years
  
  Possible duplicate of How to findout which firefox tab is using most CPU or memory?
- Admin about 8 years
  
  Five years on and nothing of the like has ever been provided by Firefox. Those users interested in having such a feature are encouraged to back this feature request.
- Admin about 8 years
  
  Add statically-updated, per-tab CPU and RAM monitor
chris over 13 years

Yes to both, as well as ad-block plus. But there's still something that's periodically using CPU.
farfromhome over 13 years

Then my next thought would be JavaScript-heavy sites that you allow through NoScript.
dangowans almost 12 years

Unfortunately the asker is using Firefox 3.x. :(
chris over 11 years

I'll settle for any version of firefox :)
peterflynn almost 11 years

Obviously it's not the same as CPU usage, but in my experience they're very often correlated. After killing the biggest memory-hogging tab, CPU usage & lagginess often drop noticeably.
Synetech over 10 years

Obviously it’s not the same as CPU usage, but in my experience they're very often correlated. @ytpete, then you frequent a narrow subset of webpages because there is absolutely no reason that they would necessarily be linked. It’s simple enough to have a 1KB webpage that has JavaScript with an infinite loop and thus 100% CPU load and another with 100MB of images that uses no CPU.
Synetech over 10 years

about:memory shows Firefox's memory usage details. There's also a button on that page that allows you to minimize memory usage. Does that page have CPU load information? If not, then what does this have to do with the question asked? This “answer” should be a comment, not an answer.
peterflynn over 10 years

@Synetech It's been many years since a simple JS infinite loop would do much: Firefox and most other browsers put up an "unresponsive script" message after a few seconds of that, and then the loop gets cut off.
Nick about 10 years

This worked great for me. While it's true that a small Javascript loop can hit the CPU without using memory, that's not what what most webpage scripts are doing -- they are making remote calls, updating and manipulating the DOM, getting invoked by plugins (like Flash), etc. All these things can result in increased memory usage (especially if the page is slowly leaking objects). I found the culprit tab, closed it, used the Minimize Memory button, and Firefox was running smooth. Thanks again!
Luís de Sousa almost 10 years

Well mate, it seems to me this question is about CPU usage, not memory...
joeytwiddle about 9 years

You might also have some success using the memory cleanup buttons in about:memory. I don't know if they will work as well as restarting Firefox. I would love to see some research on that.
joeytwiddle almost 9 years

Thanks for testing. :) <plug> I use my own Hibernate Idle Tabs userscript with Greasemonkey. It navigates to a light holding page after the tab has been unused for some hours. Hibernation can be forced with its bookmarklet.
chaostheory almost 9 years

I don't have Flash installed and I have NoScript installed. This still happens on OSX even though I have two CPUs with 8 cores and 32 GB of RAM
Luís de Sousa almost 9 years

Apparently, this profiler was never introduced. The link provided is dead at this moment.
Thalys almost 9 years

Link is there but slow
ﾤﾡ about 8 years

It has nothing to do with CPU consumption.
Burgi about 8 years

This really should have been a comment as it obviously requires clarification from the OP.
Ed Randall over 6 years

Unfortunately not yet compatible with Firefox 57.0+
ﾤﾡ almost 6 years

How does it address the question, i.e. finding the particular tab?
Matthias Urlichs almost 5 years

That's nice. However, I have a 100% CPU "Web Content" process which doesn't show up here.
Pau Coma Ramirez over 3 years

Perhaps about:processes may show a process (group of tabs) which doesn't show up in about:performance