Ways To Reduce Firefox's High CPU Usage

Ways To Reduce Firefox's High CPU Usage
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If you browse the web with Firefox, you may have noticed that on occasion it stalls or is unresponsive. Sometimes, just opening a new tab or loading a page with videos will cause the web browser to slow down or even cause other programs on the computer to not respond. One possible reason for this is that Firefox is drawing resources from the CPU to perform certain functions. In some instances, Firefox may be using so much of the CPU that it freezes the computer. There are several aspects of Firefox which require a tremendous amount of CPU resources, but there are ways to reduce this.

What is the CPU and How To Check Firefox’s Impact on It

CPU stands for Central Processing Unit. It is the part of the computer that carries out the instructions contained in a program. When you click on an icon on the desktop, the instructions to open it and display it on the screen are processed by the CPU. When you’re browsing the internet with Firefox, each time a page loads, the CPU is working.

To see the impact of programs on the CPU, use the task manager. To access the task manager, right-click on the toolbar at the bottom of the screen and select task manager. In the Windows Task Manager window, there are several tabs. The Applications tab shows which programs are running, while the Processes tab shows instances of a program being executed. It is this tab which gives you an idea of how much CPU a particular program is using. It displays the percentage of the CPU that is being used and the memory it requires. To see how much Firefox is using, search for the firefox.exe file. To quickly locate it, press the ‘F’ key. Normally, when Firefox is idle, the CPU usage is zero. When opening Firefox, loading pages, and downloading files, the CPU usage rises.

There is another tab in Windows Task Manager which displays the CPU usage. The Performance tab monitors the overall CPU usage and the physical memory usage.

Plugins Increase CPU Usage

When loading certain web pages, Firefox may draw an abnormally large amount of CPU resources. This is usually due to the type of content on the web page and how the web page was constructed. Firefox uses plugins to view certain content. For example, Youtube.com and similar sites feature flash content. To view this content in the Firefox web browser, a flash plugin is required. When the page loads, Firefox uses more CPU to display the flash content. One way to avoid this impact on the CPU is to disable flash content on certain websites. To do this use the add-on Flashblock.

Another plugin which increases CPU usage is Adobe Reader. It is used to display PDF files in the Firefox web browser. When a PDF file is opened, the impact on the CPU is considerable. One way to reduce this is to open PDF files outside the web browser. Follow these steps to do this:

  • Open Adobe Reader and click the Edit menu.
  • Go to Preferences and in the left pane select Internet.
  • Uncheck ‘Display PDF in Browser’.

Websites with a lot of JavaScript cause Firefox to use more CPU resources. There is an add-on which lets you enable and disable JavaScript on web pages. NoScript is the name of the add-on.

Firefox Is High All The Time

If Firefox is using enormous amounts of CPU resources all the time, not just when visiting specific sites or loading specific types of content, then something else might be wrong with the web browser. One area to consider is extensions. Extensions are not all the same and Firefox may have trouble incorporating extensions developed by different developers, due to different standards and lack of support for Firefox updates.

Some features of your computer’s video card or drivers may also contribute to high CPU usage. Specifically, aspects of hardware acceleration, including cursor and bitmap, may cause problems when Firefox displays images. Disabling hardware acceleration may reduce CPU usage.

Check to see if Firefox is running in Windows Compatibility Mode. This is known to cause Firefox to use a lot of CPU. Find the firefox.exe file in C:\Program Files\Mozilla Firefox and right-click it. Select Properties. In the properties window, click the Compatibility tab. The box under Compatibility Mode should not be checked. If it is, uncheck it.

One more area to check is Windows Prefetch. This is used in the boot up process and it may cause Firefox to use more CPU than necessary. To remove prefetch elements, go to C:\Windows\Prefetch\ and delete filenames that begin with FIREFOX.


Firefox Consumes A Lot of Resources - https://support.mozilla.com/en-US/kb/Firefox

Image Credit - Screenshot taken by author.