I loved this extension on chrome and used to use it all the time. However, on Firefox, this thing absolutely shreds my CPU. When loading a new page or toggling the dark-mode on, it will spike to ~80% CPU usage for several seconds, and cause my entire browser to hang (note that this is on a 5th gen i7). I don't care for extensions that abuse my CPU power. This extension never used to be like this, but I've had to stop using it.