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What is a Key Card?

Ken Black
Ken Black

A key card is a card with a magnetic strip that is inserted into a locking device to unlock a certain door or group of doors. These cards often look much like credit cards, with the same size and shape, along with the magnetic strip along the back side. They are most often used in settings where different levels of security are needed or where locks may need to be changed frequently.

Most people are familiar with a key card from a stay at a hotel. Indeed, their popularity means that they have replaced nearly all standard locks and keys at hotels in the United States and many other parts of the world. Still, this is not the only application in which they are used.

Woman holding an optical disc
Woman holding an optical disc

The card is also used to provide different levels of security. For example, if one worker has access to one part of a building but not another, there are several ways that could be handled. In the past, workers with extensive access would likely need to carry several keys — one for each level. A key card could be encoded for access at different levels, eliminating the need for multiple keys.

Some who have received a key card at a hotel or other business may be suspicious that the card may hold personal information, such as names and credit card numbers. This is not true, according to John Sileo, an identity theft expert. He notes that the only information usually put on a card is the name, room number, and perhaps a partial address of the guest. All other information, such as the guests' financial information, is kept in a separate database.

In fact, is is thought that this type of security may actually be an enhancement for privacy. Traditional hotel keys usually came with a room number engraved on the key or at least attached to a tag. Anyone who gained possession of the key would have a room number as well. Key cards do not have a room number, but rather usually come in a sleeve with the room number on it, which can be separated from the card. In addition, they can quickly be deactivated when they are lost or if the guest checks out.

When a guest is given card keys at a hotel, they have been run through a programming machine that inputs information onto the magnetic strip. This software then sends information to the locking mechanism, which sets a specific time for the key to work. Usually, it will deactivate on the checkout day at or near the checkout time. Those wanting to extend their stay will likely need a new card with new information. Programming is a relatively quick and simple process, so the inconvenience is minimized.

Discussion Comments


@Denha, I don't think that you can wreck the strip that way, but I have heard you can do so by accidentally getting an actual magnet on the strip. It's one of those reactions you get from different magnets connecting.


When I was little and my family was staying in hotel, I unwittingly took the two hotel key cards we had been given and stuck the magnetic strips together. Supposedly this was supposed to make them unusable, but I don't remember if they did or not.

However, since then I've never done that again.

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