Today, most smartphones running Android (Google) and iOS (Apple) are NFC capable.
To turn NFC on on your device, go to your device settings, then the Connection Preferences and turn on the NFC toggle. As a result, you allow the exchange of data when your device is in contact with an NFC chip or another NFC capable device.
For some devices like iPhones (from the iPhone 7), NFC is on by default and can not be turned off.
Regarding iPhones, background reading is only active from the iPhone XS. For the previous models, you have to turn on the functionality from the Control center in order to be able to read an NFC chip.
