Someone else will probably provide a better answer. I am not aware of such a debugging feature (monitoring CPU use) built into firefox. * have you seen [[firefox consumes a lot of CPU resources]] If this occur in firefox [[safe mode]] there is a problem that needs investigating. ----- Do not forget to watch the number of instances of ''plugincontainer.exe'' that are open, there is a known bug causing problems with that see [/questions/812618] Note also you are able to for instance turn off the hardware acceleration, or by setting a preference (''html5.parser.enable;true/false'') turn off the html5 browser ability of Firefox. Presumably you have seen the Web Developer options from the firefox button. (And maybe considered firebug add-on, depending on what you are trying to check)