ISO 14443 is an international standard governed by the ISO defining the physical characteristics and working interaction between contactless (proximity) tags and devices operating at 13.56 MHz (NFC – RFID) at up to 10 cm in distance. ISO 14443 is the underpinning standard for many types of NFC tags and devices, although not often directly used by developers as the specific details are abstracted by other higher-level technology layers. Within 14443, a tag is referred to as a PICC (proximity integrated circuit card) and a device as a PCD (proximity coupling device).
There are two types of tags within ISO 14443, Type A and Type B. Both of these tag types communicate via NFC at 13.56 MHz, but differ in the modulation, coding, initialization procedures and other technical details. Initially these types were thought of as competitors within the NFC industry with large organizations pushing and backing one vs. the other. However as of the late 2010s Type A is by far the most commonly used.