Hey there, You posted in the iOS forum, so I moved the thread to desktop. Can you try launching Firefox in [[Use Troubleshoot Mode in Firefox|Troubleshoot Mode]] and observe your memory and CPU usage? Extensions and themes can cause Firefox to use more system resources than it normally would and Troubleshoot Mode helps run Firefox without extensions so you can see if it's the culprit. More about high CPU usage in Firefox -> [[Fix Firefox using too much memory or CPU resources]]