Firefox, at times, may require lots of CPU power to run, which may lead to overheating issues with some consumer electronics.
According to
this Mozilla support page, entitled "Firefox consumes a lot of CPU resources," Firefox, at times, may require ample amounts of CPU resources to download, process, and display web content. The increase in CPU usage can have a direct increase on heat, especially in mobile notebook computers and smaller desktop machines.
Not only does the CPU usage increase affect the temperature of the system, it also affects the performance. The CPU is required for every process on the computer, including any and all background processes that are required to run the operating system. So, when the usually minimal CPU usage of the operating system is combined with the CPU usage of other running applications (i.e. Web Browser, IM Client, Voice/Video Chat software, etc.), the CPU is being used more. This directly affects the computer's performance, causing future processes to perform more slowly than before.
The support page cites several possible reasons for increased CPU usage from Firefox. If the increased CPU usage is occurring on only a few websites, the support page states that it could be caused by a plugin required by that page, like Flash, Java, or Adobe Reader. However, if it is occurring on several sites (or all sites visited), the support page states that it is probably caused by some setting on the computer. Extensions have been known to increase the CPU (and Memory) usage of the browser, and other settings like Hardware acceleration of the mouse pointer, Windows Compatibility settings, and more can cause the increase.
Mozilla recommends that Firefox users monitor their CPU and Memory usage while using Firefox by going to the appropriate locations in their operating system for monitoring performance data. In Windows, the user can go to the Performance tab of the Task Manger (Ctrl-Alt-Del or Right-click taskbar and select "Task Manager) to monitor CPU and memory usage.
