Mobile Fundamentals · Wi-Fi & Bluetooth · Lesson 4 of 4

NFC & Tap to Pay

The 4-centimeter radio behind contactless payments.

Really short range

NFC, short for Near Field Communication, is a radio designed to work only at very short distances. In practice that's about 4 centimeters (1.5 inches), so you more or less have to touch your phone to the reader. Bluetooth and Wi-Fi, by comparison, work across a room.

The reader creates a small magnetic field. A card or sticker inside that field can draw power from it, which is how a transit card or hotel key card works with no battery. Your phone can pretend to be a card, or it can read NFC tags itself.

Everyday uses include:

• Tap to pay at a checkout
• Tapping through a transit gate
• Reading NFC stickers and smart posters

The tiny range is a big part of the security. Someone would need to get a reader right up against your phone. Phones also ask you to confirm most payments with Face ID, a fingerprint or your passcode. Some transit features, such as Apple's Express Mode, skip that step on purpose so you can get through the gate quickly.

Your card stays secret

When you add a card to Apple Pay or Google Pay, your bank and card network create a stand-in card number just for that phone. It's called a token. Apple calls it a Device Account Number, and Google calls it a virtual account number. Your real card number isn't what your phone sends at the checkout.

When you tap to pay, the phone sends the token plus a one-time code made for that single purchase, often called a cryptogram. The card network links the token back to your real account, checks the code, and approves the payment. The store never receives your actual card number. Your receipt usually shows the token's last four digits, which can differ from the ones printed on your card.

This system is called tokenization, and it pays off when a store gets hacked. A stolen token can't be used without a fresh code from your phone, and your real card number was never on the store's systems to steal. If you lose your phone, you can remove its cards remotely and keep using your physical card.