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Multiple instances of Firefox

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  • Last reply by cor-el

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I have used Firefox for years with a short diversion to Chrome for a few months. Despite regular restarts the browser is slow. Today I have 4 tabs open but task manager shows 10 (and sometimes 20) instances of Firefox running. Can anyone help me figure out what is going on? Thanks in advance

I have used Firefox for years with a short diversion to Chrome for a few months. Despite regular restarts the browser is slow. Today I have 4 tabs open but task manager shows 10 (and sometimes 20) instances of Firefox running. Can anyone help me figure out what is going on? Thanks in advance

All Replies (3)

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More than one process is normal for the current Firefox. http://www.ghacks.net/2016/07/22/multi-process-firefox/

Multi-process Firefox is codenamed "e10s". https://wiki.mozilla.org/Firefox/multiprocess


Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

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Fred, I started in safe mode. Currently have 6 tabs open and Task manager shows 8. What should my next step be? Thank you

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You can check the Firefox Task Manager (about:performance) and about:memory pages.


It is quite normal to see more Firefox processes running.

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

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.