Eli5: How does the tap feature work for credit/debit cards?


When you tap a credit card How does it read all your card information?

In: 2


There’s a little tiny computer circuit built into the credit card with a radio antenna. On most cards you can see it – it’s a little silvery rectangle near one end. The card reader sits there projecting radio waves around itself, and when you put your card near the reader the card “catches” some of those waves and uses them to power up, then sends some different radio waves back in return. The returned radio waves contain the information needed to identify your card so you can make a payment.

This technology is called “Passive Near-Field Communication” if you’d like to read more.

It’s like wireless charging. Then the little chip in your card gets near the terminal an electric field makes it come to life and transceives information with the card company.

For security the card has built in keys that will never be used twice but also, never be guessed at random.