How hotel key cards work: RFID, NFC and the door lock
Updated
Most modern hotel room keys are contactless RFID cards that work at 13.56 MHz, the same frequency and standard that NFC builds on. That is why most hotel cards can be detected by an NFC reader, including many Android phones. Not all of them, though: some hotels still use magnetic-stripe cards, and a few use low-frequency (125 kHz) cards that NFC can’t see.
How a key card opens a door
When reception issues a key, the hotel’s door-lock system writes data onto the card: which room or areas it opens, and for how long. On most systems the door lock checks that data itself and works offline, without contacting the PMS. Some newer, networked locks also check online.
This splits what the hotel knows between two systems. The PMS (OPERA, Mews and the like) knows the reservation: who is staying, in which room, on which rate. The lock system knows which card belongs to which room. Anything that wants to recognise a room key, say at the restaurant door, has to work with the lock system’s interface rather than the PMS.
A phone can often read a card’s identifier over NFC, but not the protected data the lock uses. Many lock systems also offer mobile keys, where the guest’s phone opens the door.
At breakfast
Because nearly every guest carries their key card down to breakfast, it is a convenient way to identify a room without asking for a number. Where Kløvr is connected to the lock system, the guest can tap their room key on a tablet at the restaurant door. A small Kløvr program on the hotel’s network asks the lock system which room the card belongs to. It only reads; it never creates or changes keys. If the lock system isn’t connected, the guest types their room number instead.
Related
Kløvr registers breakfast at the restaurant door and writes it back to OPERA Cloud or Mews.