There are four basic tag types that have been defined. These are given designations 1 to 4 and each has a different format and capacity. These NFC tag type formats are based on ISO 14443 Types A and B which is the international standard for contact-less smartcards) and Sony FeliCa which conforms to ISO 18092, the passive communication mode, standard).

The advantage of keeping the NFC tags as simple as possible is that they may be deemed to be disposable in many instances, often embedded in posters that may only have a short life, etc.

The different NFC tag type definitions are as follows:
Tag 1 Type:   The Tag 1 Type is based on the ISO14443A standard. These NFC tags are read and re-write capable and users can configure the tag to become read-only. Memory availability is 96 bytes which is more than sufficient to store a website URL or other small amount of data. However the memory size is expandable up to 2 kbyte. The communication speed of this NFC tag is 106 kbit/s. As a result of its simplicity this tag type is cost effective and ideal for many NFC applications.
Tag 2 Type:   The NFC Tag 2 Type is also based on ISO14443A. These NFC tags are read and re-write capable and users can configure the tag to become read-only. The basic memory size of this tag type is only 48 bytes although this can be expanded to 2 kbyte. Again the communication speed is 106 kbit/s.
Tag 3 Type:   The NFC Tag 3 Type is based on the Sony FeliCa system. It currently has a 2 kbyte memory capacity and the data communications speed is 212 kbit/s. Accordingly this NFC tag type is more applicable for more complex applications, although there is a higher cost per tag.

Tag 4 Type:   The NFC Tag 4 Type is defined to be compatible with ISO14443A and B standards. These NFC tags are pre-configured at manufacture and they can be either read / re-writable, or read-only. The memory capacity can be up to 32 kbytes and the communication speed is between 106 kbit/s and 424 kbit/s.

From the definitions of the different NFC tag types, it can be seen that type 1 and 2 tags are very different to type 3 and 4 tags, having different memory capacity and makeup. Accordingly it is expected that there is likely to be very little overlap in their applications.

Type 1 and type 2 tags are dual state and may be either read/write or read-only. Type 3 and Type 4 tags are read-only, data being entered at manufacture or using a special tag writer.