NFCtags

NFC tags are small passive devices that combine an integrated circuit with an antenna. They store a small amount of data and are powered entirely by an NFC reader’s radio field, requiring no battery. When the tag is brought into proximity (a few centimeters) of an NFC-enabled device, the device can read or write data depending on the tag’s configuration.

Data is typically stored in an NDEF message, which can contain a URL, a short text, a vCard, or other MIME types. NDEF provides a standardized data format for exchange. Tags vary in memory, from tens of bytes to several kilobytes. Common consumer tags range from 48 to 512 bytes of usable memory, though higher-capacity tags exist.

Tag types: NFC Forum defines several tag types. Type 1 and Type 2 are based on ISO/IEC 14443-A; Type 3 is based on Sony’s Felica; Type 4 is ISO/IEC 14443-4 and can support secure elements and NDEF; Type 5 (ISO/IEC 15693) covers longer-range tags. Many devices support reading Type 2 and Type 4 tags. Some tags are write-once; others are rewritable; memory can be locked to prevent further writes.

Security and privacy: data on NFC tags is accessible to any compatible reader within range, so sensitive information is often avoided or protected with access control, encryption, or storing sensitive data on secure elements (in Type 4 tags) rather than in plain NDEF records.

Applications: contactless business cards, product labels, tickets, smart posters, and simple access-control identifiers. Limitations include short read range, limited memory, and dependence on reader compatibility, though interoperability is ensured by NFC Forum standards.