Firefox uses around 1 to 2GB of RAM and around 25% of the CPU with just around 10 tabs open along with a YouTube video. A chromium based browser on the same system and the same tabs open uses around 400MB of RAM and around 10% of the CPU. Safari with the same tabs is even more efficient I have tested this with safe mode, on another system with the same hardware but couldn't find what's causing the problem. I have uninstalled all dynamic themes as well. Firefox does not use this kind of resources on windows or linux but uses something more close to chromium numbers (tested on a desktop PC, AMD Ryzen 3 3200G) While I do not expect Safari levels of optimization, this problem only arising on Apple Silicon Macs is a problem worth solving. This is the only thing that's keeping me from using firefox as a daily driver and supporting the open web.