Stop Firefox from Consuming CPU Cycles

Firefox has a reputation as a resource hog, and it's tough to bring it down to the level of a leaner browser. That said, if your CPU use shoots to 100% during basic browsing, there's something wrong. Make sure to check your installed extensions and plugins, and to change any system settings if necessary.

Steps

Troubleshooting Extensions

  1. Start-Firefox-in-Safe-Mode. Enter about:support in your address bar to visit the Troubleshooting Information page. Click Restart with all add-ons disabled. When the pop-up window appears, select Safe Mode. All add-ons will be disabled during this session. Browse as you would normally, and check your CPU cycles. If Firefox uses many fewer cycles in safe mode, continue to the next step.[1] Otherwise, try another method.
    • You can also reach this page by clicking the menu icon, then the question mark icon, then Troubleshooting Information.
  2. Disable an extension. Quit and reopen Firefox to return to normal mode. Enter about:addons in the address bar to visit the Add-Ons Manager. Click the Extensions tab and choose Disable to temporarily turn off one extension. If prompted to restart Firefox, do so. Browse for a while with the extension disabled, checking your CPU usage.
    • This page lists extensions with known problems, plus solutions. The list is not complete or up to date, but it's a good starting point.
    • The most common culprits are antivirus, ad-blocking, and Adobe Reader add-ons. Test these first.[2]
  3. Repeat with other extensions. If CPU usage hasn't dropped, disable another add-on and keep browsing. Repeat until your CPU usage drops. The last add-on disabled may be the problem. Keep it disabled until you need to use it.[Image:Stop Firefox from Consuming CPU Cycles Step 3 Version 7.jpg|center]]
    • A large group of add-ons can hog your CPU even if no single add-on is defective. If this is the case, disable anything you don't use often.
  4. Return to the default theme. If your problem still isn't solved, a custom theme could be causing problems. Visit the Appearance tab in the Add-Ons Manager, and switch to the default theme.

Troubleshooting Plugins

  1. Update your plugins. Visit https://www.mozilla.org/en-US/plugincheck/ to check the status of your plugins. If you see any Update Now buttons, click them and wait for them to update. Restart Firefox once finished. Plugins can increase CPU usage when you view videos, PDFs, or other media.
  2. Adjust plugin behavior. Once all of your plugins are up to date, testing them is pretty easy:
    • Visit the Plugins tab of the Add-Ons manager.
    • Click each drop-down menu that says "Always Activate" and set it to "Ask to Activate" instead.
    • Browse as usual. You will see a small popup every time a plugin asks to be activated. If you say "Yes" and your CPU usage rises, that plugin is the problem.
    • When the problem is identified, look for alternative plugins for the same format. If there are none, leave that plugin in "Ask to Activate" mode.
  3. Install new extensions to disable problem content. One solution is to block media you don't want to see in the first place. Try these extensions:
    • If Flash causes the problem, install Flashblock.
    • If JavaScript causes issues, install NoScript. This will take some hands-on effort at first to disable problematic scripts one by one.
    • For a generally lower CPU load, install Adblock Plus or another ad blocker.
  4. Reset Firefox. If all else fails, return your Firefox to default state. This will permanently delete your add-ons, but most preferences and bookmarks should remain unchanged. To do this, return to about:support and click Refresh Firefox.
    • You may want to try the other issues below before you resort to this. If Safe Mode fixed your issue, however, add-ons are almost certainly the problem.

Other Solutions

  1. Change your Firefox version. Check your Firefox version to automatically update to the latest version. If you've already updated, download the Firefox Beta instead. The Beta includes in-progress bug fixes that have not yet made it to regular Firefox.
    • Reverting to older versions of Firefox is not recommended. They may have security risks.
  2. Remove malware from your computer. If you see popups and other ads on every web page, your computer is infected with malware. Even if there are no obvious signs, running an antivirus scan is recommended. Malicious software may have accessed your CPU.
  3. Disable Windows compatibility mode. If you are on Windows, right-click the Firefox icon on your desktop. Select Properties, then the Compatibility tab. If the checkbox underneath Compatibility Mode is checked, uncheck it and restart Firefox.[3]
  4. Toggle hardware acceleration. Hardware acceleration assigns your graphical processing unit some of the hard work, theoretically freeing up your CPU. This generally works as intended on Firefox, but it can backfire on certain websites or on computers with an older OS or graphics card.[4] Try a day with hardware acceleration and a day without, to compare the effect:
    • Enter about:preferences#advanced in the Firefox address bar, or click the menu icon (three lines), then Preferences, then the Advanced tab.
    • Check or uncheck "Use hardware acceleration when available."
    • Restart Firefox.[5]
  5. Toggle hardware acceleration for Flash videos. Your Flash player may use hardware acceleration even if Firefox has disabled it. Right-click on a Flash video and select Settings. Click the far left tab (Display) and check or uncheck "Enable hardware acceleration."[6] Adjust this to match your Firefox setting.
    • Some video hosts now use an HTML5 player instead of Flash. This should adjust correctly to your Firefox settings.
  6. Disable WebGL. WebGL is a similar hardware acceleration technology, mostly used for graphic-intensive uses like 3D browser games. It has been known to consume CPU cycles in the past, but these problems are rare in modern Firefox. You could try disabling it just in case:[7]
    • Enter about:config in the address bar. As the warning says, you should not change any settings here without knowing what you're doing.
    • Search for webgl.disabled. (Don't confuse this with other similar settings.)
    • Double-click that row to change the value to True.
    • Restart Firefox.



Tips

  • Hardware acceleration usually reduces CPU cycles, but it may or may not reduce overall energy consumption.
  • Hardware acceleration may be more effective if you update your video card drivers.

Related Articles

Sources and Citations

  1. ↑ https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
  2. ↑ https://support.mozilla.org/en-US/kb/disable-built-pdf-viewer-and-use-another-viewer
  3. ↑ http://kb.mozillazine.org/Firefox_CPU_usage
  4. ↑ https://helgeklein.com/blog/2014/12/impact-gpu-acceleration-browser-cpu-usage/
  5. ↑ https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix
  6. ↑ http://www.macromedia.com/support/documentation/en/flashplayer/help/help01.html
  7. ↑ https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration#w_disabling-webgl
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