Keycards are the major elements of the game, being the only items that can open doors by inserting the card at the slot. Keycards can be found in various places or get refined through SCP-914 to create other keycards. There are six keycard levels, 1 through 5 plus Omni. Level 0 is not in the game but it exists.
Level 2
Level 2 keycards can be used to open the doors to SCP-914's containment chamber. It's found in the basic office or at the small testing room. It can also be obtained by placing a level 1 keycard into SCP-914 on "Fine" or a MasterCard/Playing Card on "Very Fine".
It's a safe access keycard.
Level 3
The level 3 keycard can be used to open the main door and the door to the staircase in SCP-106's chamber, SCP-895's chamber, SCP-079's chamber, SCP-012's chamber, the first door leading to SCP-714's and SCP-1025's chambers, The level 3 keycard can be obtained by placing a level 2 keycard in SCP-914 on "Fine". It is found in SCP-895's chamber.
This accesses all Euclid level SCPs.
Level 4
The level 4 keycard is found in SCP-049's containment chamber, right next to SCP-049's document. It is required to access the head office. As of v0.8, this keycard can no longer be obtained with SCP-914; making obtaining a Level 5 Keycard more difficult.
This accesses all Keter and Euclid level SCPs.
Level 5
The level 5 keycard is required to open the door to the elevator leading to the warhead room, the door leading to the small control room in the warhead room, and the door in the checkpoint room between the Heavy Containment Zone and Entrance Zone. It can be found in the head office, next to the control panels which captures 106 or obtained by placing a level 4 keycard in SCP-914 on "Fine".
Can access all doors.
Omni Card (Access To All Doors That Handle Keycards)
The Omni keycard currently has no unique use, but can access anything requiring a keycard and is one of the optional objectives at the endgame. The Omni keycard can only be obtained via placing a level 5 keycard through SCP-914 on "Fine" or by placing any level keycard through SCP-914 on "Very Fine", however the chance of producing a MasterCard or Playing Card instead is significant. An achievement is awarded after obtaining the Omni card.