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Firefox task manager does not match Windows Task Manager

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  • 1 has this problem
  • Last reply by cor-el

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With 8 tabs open, Windows task manager shows 58% CPU and 1279 MB memory use in 12 processes. The built in Firefox task manager shows less than 300 MB and mostly "low" energy impact. Why is there such a discrepancy between the two task reports?

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FireFox displayed too many times in the Task Manager For the last month or so, FireFox has repeatedly crashed when more than two tabs are open and at least one of the tabs is a video from YouTube. I have found several work-arounds and suggestions to tweak FireFox to behave better and they have worked with solving the crash problem.

However, with only one application of FireFox open and only one tab in the application, Task Manager is reporting that FireFox is actively more busy than what it actually is as portrayed in my screenshot:

FireFox displayed too many times in the Task Manager-firefox.jpg

How can five applications of FireFox be open when I'm only using one application of it with only one tab open? I have "Reset FireFox, I have deleted FireFox completely (even Registry entries) and reinstalled it, I have made the privacy adjustment for allowing applications to NOT have exclusive access to FireFox and still FireFox is open too many times in Task Manager for my taste.

The only thing I haven't tried is making FireFox breakfast in the morning to see if it reacts any differently; but, I'm not holding my breath on that one.

My Windows version is listed in my computer specs and underneath my avatar, so if anyone knows of something else I can try, please chime in. My FireFox version is 70.0.1 (64-bit).

Thank you!

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The Task Manager only shows what tab content processes are using.
There are other processes that aren't included on this page, so the processes with high memory use in the Windows Task Manager are likely such other processes.

For more detail about the memory use you can check the about:memory page.

It is quite normal to see more Firefox processes running.

  • one process for the main Firefox thread (user interface)
  • one or more content processes, see:
    Options/Preferences -> General -> Performance
    remove checkmark: [ ] "Use recommended performance settings"
  • one process for the compositor thread
  • one process for the WebRender when this feature is enabled

There can also be processes used by plugins like Widevine (DRM) and Flash.

You can find the current multi-process state on the Troubleshooting Information page (about:support).

  • "Help -> Troubleshooting Information" -> "Application Basics":
    Multiprocess Windows
    Remote Processes

See also the Remote Processes section further down for more detail.