NDEF (NFC Data Exchange Format)

What Is NDEF?

NDEF (NFC Data Exchange Format) is the standardized data format defined by the NFC Forum for organizing, storing, and exchanging information on NFC tags and between NFC devices. NDEF provides a universal container format understood by all NFC-enabled smartphones regardless of manufacturer or operating system.

NDEF Architecture

NFC Tag Memory
  +-- Capability Container (CC)
  +-- TLV Wrapper
       +-- NDEF Message
            +-- NDEF Record 1 (e.g., URI)
            +-- NDEF Record 2 (e.g., Text)
            +-- NDEF Record N (e.g., AAR)

An NDEF message contains one or more NDEF records. Each record carries data with type identification. The message is wrapped in TLV encoding and preceded by a capability container.

Common NDEF Record Types

Why NDEF Matters

Before NDEF, contactless applications required custom software with proprietary formats. NDEF solved this by establishing a format that works everywhere (any NFC phone, no app required), is self-describing (records carry type metadata), composable (multiple records per message), and compact (URI prefix compression minimizes memory usage).

NDEF Formatting

Tags must be "NDEF formatted" before storing messages. Formatting writes the capability container and initializes the TLV structure. Most NTAG and MIFARE Ultralight chips ship pre-formatted. DESFire and ICODE chips require an initial formatting step.

Memory Usage

A simple URL like https://example.com requires ~15-20 bytes (including TLV overhead and URI prefix encoding). Complex payloads like vCards may require 200-500 bytes. Ensure your payload fits within the chosen chip's user memory.