NDEF
The standard data format for NFC tags, defining how information like a URL is encoded so any compatible phone reads it consistently.
NDEF (NFC Data Exchange Format) is the standard format used to store data inside an NFC tag. It defines a consistent record structure so every NFC-capable phone interprets the content the same way.
The most common record type is a URI (web address): when a phone reads a tag with this NDEF record, it immediately offers to open the URL - no dedicated app needed.