Key

Keys are used to open designated locked doors. If the player encounters a locked door and attempts to open it without the correct key, the door will not open and the player will get a message saying so. Once a key is obtained, any locked door of corresponding color on the map can be opened. Keys are lost upon map exit.

Doom also does not differentiate between keycards and the skull keys, though this was later changed first in the Boom source ports and is now the norm for most major ports.

Stats for IWADs
Blue keycard Red keycard Yellow keycard

Blue skull key Red skull key Yellow skull key