Task Manager - see whether tabs or extensions are slowing down Firefox

Firefox's Task Manager feature lets you see which tabs or extensionswhether tabs, extensions or other processes are using a lot of memory or energy impactCPU resources. This feature can be useful when diagnosing high CPU or memory usage in Firefox.

To open the Task Manager, click the menu button fx89MenuButton, click More Tools and click Task Manager. The Task Manager about:processes page will open in a new tab.

Fx107ProcessManagerTab

Tip: You can also enter about:processes in the address bar or use the keyboard shortcut Shift + esc to open this page.

To open the Task Manager, click the menu button fx89MenuButton, click More Tools and click Task Manager. The Task Manager about:performance page will open in a new tab. taskmanager_fx68

Tip: You can also enter about:performance in the address bar to open the Task Manager.

Use the Task Manager

The Task Manager can display useful information about the tabs and extensions actively running on Firefox. This information is displayed in multiple columns:

  • Name displays the name of the tabs and extensions currently running within Firefox. Extension IDs will also be included in this column.
  • Type indicates whether the item listed is a tab or an add-on.
  • Energy Impact shows the processing power being used by the CPU. Tasks with a higher energy impact will drain your battery quicker and may slow down the performance of your system.
  • Memory shows the amount of RAM that the given task uses currently on your system.

View subtasks

Some tabs have additional subtasks that can be viewed from the Firefox Task Manager. These may include subframes, trackers or service workers associated with the tab.

To view subtasks select the right-arrow on the left side of the task's name. You can hide the subtasks again by selecting the down-arrow on the left side of the main task's name.

Perform actions

Hovering over an item in the Task Manager will show more details about the performance of this tab or extension. The action button will also appear on the right side of the task.

The action button can perform the following:

  • On Tab Tasks: Close the associated tab.
  • On Add-on Task: Open the add-on page in a new tab.
Note: Actions cannot be performed on subtasks.

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