Do you want to enable/ disable full-screen mode in Firefox, here is how to enable and disable Full screen mode in Firefox web browser
Full screen mode turns off the Status Bar, the Title Bar, Task Bar and turns your browser in to a full screen.
How to enable full-screen mode in FireFox
Method 1 :
Press the F11 button on your keyboard to turned on and off full screen
Go to View >> select Full Screen to turn on full screen. Press F11 button to turn off.