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

Open the Task Manager

1. Click the menu button The image "fx57menu" does not exist..
2. Click More.
3. Click Task Manager. Task Manager will open in a new tab.

Using 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 the performance of your system.
• Memory shows the amount of RAM that the given task is currently using on your system.

Viewing 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.

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

Performing actions

Hovering over an item in the Task Manager will show more details about that that tab or extension's performance. 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.