How NFC IC card scanning works
Japanese IC cards use FeliCa, a contactless standard that phones can read directly over NFC.
The chip powers itself
The card has no battery. The phone creates a small radio field, the card antenna draws power from it and answers back. That is why the card has to sit close to the phone antenna and stay still for a moment.
Where the antenna sits
- iPhone: the top edge on the back of the phone.
- Android: usually the middle of the back, sometimes higher up.
- Move the card slowly if the first spot does not respond.
What is read
The app requests two blocks of data: the current balance and the history log of roughly the last twenty events. Each history entry contains a date, an amount, a type such as a train trip, a purchase or a top up, and for trips the codes of the entry and exit stations.
Everything happens on the device. Nothing is uploaded, and the read works with no internet connection at all.
Common questions
Is scanning safe for the card?
Yes. Reading is passive, it only asks the chip for data it already holds and never writes to the card or changes the balance.
Why does my iPhone show a scan sheet?
iOS runs NFC reads through a system sheet. It appears automatically when the scanner starts and closes when the card has been read.
Why do some stations show as codes?
The chip stores numeric line and station codes rather than names. The app translates them using a bundled lookup table, and rare or new codes may not have a name yet.
Next
Step by step balance check or see which cards are supported.