In full screen mode, all Firefox toolbars are hidden, with the exception of the Address Bar. This allows the webpage you are viewing to fit the size of your screen.

Below are two screenshots of the same webpage. The first is taken in normal view, while the second is taken in full screen mode. The orange highlights indicate the toolbars that are hidden when in full screen mode.

 

Normal View – Click to Enlarge

 

Full Screen – Click to Enlarge

 

To switch to full screen mode, go to the top of your Firefox browser and click View > Full Screen. Or you can type F11 on your keyboard:

 

 

To leave full screen mode, type F11 on your keyboard once again.