There is no exact data that defines how much RAM Firefox should take. The consumption of RAM by a web browser depends on the number of tabs you open and the websites you visit. If the website that you visit uses heavy graphics, your browser will consume more RAM. Firefox can work on a computer with 4 GB RAM but you may experience performance issues with Firefox. If your system has 4 GB RAM, we suggest you install an SSD instead of upgrading your RAM. This will resolve the Firefox performance issues.