On some systems, Undertale doesn’t seem to start in full-screen mode. Instead, it takes up a small square window on your screen. This isn’t exactly an ideal way to play the game.
There are two ways to make it full screen. The first method is by pressing ALT + Enter on your keyboard. This command works for most games and programs, and will force the software to run in full screen mode.
If that doesn’t work, Undertale actually has it’s own controls built in which will allow the game to run in fullscreen. By default, this is done by pressing the F4 key on your keyboard.
You can find these settings in the controls. Where other ones are listed such as:
- Z/Enter = Confirm
- X/SHIFT = Cancel
- C/CTRL = Menu
- F4 = Fullscreen
- Hold ESC = Quit