Full screen mode is especially useful when watching online videos, reading PDFs or browsing through photos libraries. There are two ways to toggle the full screen mode of Mozilla Firefox browser. The first one involves pressing the F11, which automatically opens the current tab in full screen. The same results can be achieved by clicking on the Menu button > Full Screen:

Full Screen mode strips out the web browser of any unnecessary elements (toolbars, menus, add-ons...) and allows the user to focus on the content of the selected webpage.