Final answer:
The quickest way to mirror a laptop screen to an external display is to adjust the display settings using a keyboard shortcut, typically 'Windows Key + P', and select 'Duplicate'.
Step-by-step explanation:
The quickest way to have your laptop display mirrored instead of extended is by adjusting the display settings. Typically, this can be done by using a keyboard shortcut such as Windows Key + P on Windows computers, which will bring up a display mode menu where you can select 'Duplicate' to show the same content on both screens (your laptop and the external display). No need to reboot, use a screen mirroring app, or swap cables.