I unistalled and re-installed Firefox today. My PC is new,so i don't know if this was happening before, but i just noticed it today. Firefox opens multiple processes in my task manager. It starts at 8, and increases over time. I don't know if this is normal. I will post some pictures. Literally every single answer to this question tells me to go to config, "performance" tab, unmark the default one and choosing "1" in the other one. But i do not have this option. I don't know what to do. (Im Brazillian, so my Firefox is in portuguese. The second picture is the "performace" tab. Most of you will probably don't understand, but i just wanted to show that it does not give me the option to change the value.)