View and Start Firefox in Full Screen Mode
The easiest way to view Firefox in full screen is to simply to press F11, but for more options such as to start up Firefox in full screen and full screen without any toolbars, get the AutoHide extension.
AutoHide is a very easy to use and learn extension that will allow you to view Firefox in true full screen mode with or without any toolbars. You can also set AutoHide to start Firefox in full screen mode and easily toggle between full screen and normal viewing by pressing F11, by using a toolbar button, or by making a selection from the context menu.
To set your preferences for AutoHide, go to-
Tools > Add-ons > Extensions > AutoHide > Options
Activate Full Screen in Firefox
There are a few ways to quickly enable full screen in Firefox by using AutoHide.
Hit the F11 key
Right click and select Full Screen
Use a toolbar button.
After you've installed AutoHide and restarted Firefox, right click on any toolbar (except for the bookmarks toolbar) and select Customize. Drag the Full Screen button to the toolbar of your choice. You can toggle between full screen and the default view with any of the options above.
If you wish to start Firefox in full screen, simply close Firefox while you have full screen enabled.
When you restart Firefox, it will open in full screen mode. You can discover more options and settings by clicking on Info on the AutoHide install page.
Also, check out the Firefox keyboard and mouse shortcuts so that you can learn how to navigate and use Firefox without toolbars while you're in full screen mode.
It's All Better in Full Screen
Viewing images in normal view
Playing games in normal view
Viewing videos in normal view