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 
, click and select from the menu. The about:processes page will open in a new tab.
Information is displayed in multiple columns:
- Name: A list of current processes that Firefox is running and ID numbers that identify each process. For technical information about process types, see Process Model — Firefox Source Docs documentation.
- Memory: A rough estimate of how much computer memory each process is using.
- CPU: A rough estimate of how much of your computer's processing power each process is using.
- Gear icon: This allows you to access more options for a process, such as closing a tab.
The Extensions process entry shows memory and CPU usage for all extensions, since extensions all share a single content process. To view information for individual add-ons, enter about:performance in the address bar.
Information is displayed in multiple columns:
- Name displays the name of tabs and extensions currently running within Firefox.
- Type indicates whether the item listed is a tab or an add-on. (Some tabs have additional subtasks, that may include subframes, trackers or service workers associated with the tab).
- 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.
To open the Task Manager, click the menu button , click and click . The Task Manager about:performance page will open in a new tab.
Table of Contents
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.
