The NFC Data Exchange Format (NDEF) specification is a common data format for NFC Forum Devices and NFC Forum Tags.
The NFC Data Exchange Format specification defines the NDEF data structure format as well as rules to construct a valid NDEF message as an ordered and unbroken collection of NDEF records. Furthermore, it defines the mechanism for specifying the types of application data encapsulated in NDEF records. The NDEF specification defines only the data structure format to exchange application or service specific data in an interoperable way, and it does not define any record types in detail—record types are defined in separate specifications. This NDEF specification assumes a reliable underlying protocol and therefore this specification does not specify the data exchange between two NFC Forum Devices or the data exchange between an NFC Forum Device and an NFC Forum Tag. Readers are encouraged to review the NFCIP-1 transport protocol [ISO/IEC 18092].
An example of the use of NDEF is when two NFC Forum Devices are in proximity, an NDEF message is exchanged over the NFC Forum LLCP protocol. When an NFC Forum Device is in proximity of an NFC Forum Tag, an NDEF message is retrieved from the NFC Forum Tag by means of the NFC Forum Tag protocols. The data format of the NDEF message is the same in these two cases so that an NFC Forum Device may process the NDEF information independent of the type of device or tag with which it is communicating.
NFC Data Exchange Format (NDEF) Page 1 Overview
Because of the large number of existing message encapsulation formats, record marking protocols, and multiplexing protocols, it is best to be explicit about the design goals of NDEF
and, in particular, about what is outside the scope of NDEF.