Firefox CPU usage: Difference between revisions

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Sometimes Firefox uses excessive amounts of CPU as reported by Windows Task Manager or by the ''top'' command on Linux.
This article describes how to prevent or work around high CPU usage in Firefox.


== Excessive CPU on certain web sites ==
==Only on specific pages==
If Firefox uses lots of CPU on certain web pages, please report the problem using Help -> Report Broken Web Site. Usually there's executable code on the site that is consuming the CPU. On the other hand, if a bug in Firefox is causing the excessive CPU usage, this will help track down the problem.
=== Plugins ===
If you're only having problems with sites that use [[Flash]], use the [http://flashblock.mozdev.org/ Flashblock] extension to selectively enable or disable it.[http://momentarypause.blogspot.com/2006/02/firefox-cpu-issues.html][http://forums.mozillazine.org/viewtopic.php?t=184258]


The [http://flashblock.mozdev.org/ Flashblock] extension can help the problem by blocking [[Flash]] code that consumes excessive amounts of CPU.[http://momentarypause.blogspot.com/2006/02/firefox-cpu-issues.html][http://forums.mozillazine.org/viewtopic.php?t=184258]
If the problem happens when viewing PDFs, it's likely a problem with [[Adobe Acrobat]]. One possible fix is to create a WWW_OpenURL directory in the AdobeUM directory.[http://public.ok2life.com/welcome/index/54.html]


Sometimes [[JavaScript]] on some web pages can cause excessive CPU. You can use the [http://noscript.net/ NoScript] extension to block execution of JavaScript on problematic pages.
=== JavaScript ===
Some sites can cause high CPU usage through extensive use of JavaScript. You can disable JavaScript selectively using the [http://noscript.net/ NoScript] extension.  


== Extensions ==
=== Firefox bugs ===
Some [[problematic extensions]] can cause excessive CPU usage. See the linked article for which extensions cause this problem and possible workarounds.
Report the site using Help -> Report Broken Web Site. Reporting the problem will help Mozilla track down any bugs in Firefox.


== Hardware Acceleration ==
==All the time==
There are some reports that disabling cursor and bitmap hardware acceleration on some video cards and drivers can reduce CPU usage when displaying images.[http://forums.mozillazine.org/viewtopic.php?p=2734282#2734282]


== Windows Compatibility Tab ==
=== Extensions ===
There are some reports that Firefox can cause excessive CPU usage if it's set to run in compatibility mode for an older version of Windows.[http://forums.scotsnewsletter.com/index.php?showtopic=13873] To fix the problem, right-click on the Firefox icon you click to start Firefox, click Properties, click the Compatibility tab, make sure the check box under Compatibility mode is unchecked, and restart Firefox.
[[Problematic extensions]] can cause excessive CPU usage.


== Adobe Acrobat ==
=== Windows Compatibility mode ===
Sometimes viewing pages with Adobe Acrobat can cause Firefox to use excessive amounts of CPU. This problem may be fixed by creating a WWW_OpenURL directory in the AdobeUM directory.[http://public.ok2life.com/welcome/index/54.html]
Firefox can cause excessive CPU usage if it's set to run in compatibility mode for an older version of Windows.[http://forums.scotsnewsletter.com/index.php?showtopic=13873] To fix the problem, right-click on the Firefox icon you click to start Firefox, click Properties, click the Compatibility tab, make sure the check box under Compatibility mode is unchecked, and restart Firefox.


== Other causes ==
=== Hardware acceleration ===
* Read the [[Firefox hangs]] article for other solutions to Firefox consuming lots of CPU.
Disabling cursor and bitmap hardware acceleration on some video cards and drivers can reduce CPU usage when displaying images.[http://forums.mozillazine.org/viewtopic.php?p=2734282#2734282]
* If none of the solutions on these pages fixes your problem, you may want to file a bug report. [https://bugzilla.mozilla.org/buglist.cgi?query_format=advanced&short_desc_type=allwordssubstr&short_desc=CPU&product=Core&product=Firefox&long_desc_type=substring&long_desc=&bug_file_loc_type=allwordssubstr&bug_file_loc=&status_whiteboard_type=allwordssubstr&status_whiteboard=&keywords_type=allwords&keywords=&resolution=---&emailassigned_to1=1&emailtype1=exact&email1=&emailassigned_to2=1&emailreporter2=1&emailqa_contact2=1&emailtype2=exact&email2=&bugidtype=include&bug_id=&votes=&chfieldfrom=&chfieldto=Now&chfieldvalue=&cmdtype=doit&order=Reuse+same+sort+as+last+time&field0-0-0=noop&type0-0-0=noop&value0-0-0= This] is a list of unsolved bugs in Firefox that cause excessive CPU usage. Look through the list, and if your situation doesn't match any of the situations listed, file a new bug report. If you cannot give a set of steps that reproduces the problem, you may want to try to [http://wiki.mozilla.org/MozillaQualityAssurance:Triage#How_to_Help_with_Regressions_--_Finding_Regression_Windows find a regression window] to determine which change to Firefox caused the problem. If you're running Windows, you may also want to use [http://www.microsoft.com/technet/sysinternals/utilities/ProcessExplorer.mspx Process Explorer] to determine which thread is using most of the CPU and include this information in the bug report.
 
== See also ==
* [[Firefox hangs]]


[[Category:Issues (Firefox)]]
[[Category:Issues (Firefox)]]
[[Category:Websites]]
[[Category:Websites]]
[[Category:Performance - Firefox]]
[[Category:Performance - Firefox]]

Revision as of 20:47, 5 February 2007

This article describes how to prevent or work around high CPU usage in Firefox.

Only on specific pages

Plugins

If you're only having problems with sites that use Flash, use the Flashblock extension to selectively enable or disable it.[1][2]

If the problem happens when viewing PDFs, it's likely a problem with Adobe Acrobat. One possible fix is to create a WWW_OpenURL directory in the AdobeUM directory.[3]

JavaScript

Some sites can cause high CPU usage through extensive use of JavaScript. You can disable JavaScript selectively using the NoScript extension.

Firefox bugs

Report the site using Help -> Report Broken Web Site. Reporting the problem will help Mozilla track down any bugs in Firefox.

All the time

Extensions

Problematic extensions can cause excessive CPU usage.

Windows Compatibility mode

Firefox can cause excessive CPU usage if it's set to run in compatibility mode for an older version of Windows.[4] To fix the problem, right-click on the Firefox icon you click to start Firefox, click Properties, click the Compatibility tab, make sure the check box under Compatibility mode is unchecked, and restart Firefox.

Hardware acceleration

Disabling cursor and bitmap hardware acceleration on some video cards and drivers can reduce CPU usage when displaying images.[5]

See also

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