Compare user memory, then verify the message
| IC | User memory | Selection decision |
|---|---|---|
| NTAG213 | 144 bytes | Consider when the complete message fits within the available user area. |
| NTAG215 | 504 bytes | Consider when the complete message exceeds NTAG213 capacity. |
| NTAG216 | 888 bytes | Consider when the complete message needs more space than NTAG215 provides. |
Memory is measured in bytes, not visible characters. NDEF headers and the tag data structure consume space. Measure the actual encoded message with the intended encoder; do not choose from a URL character count alone.
Memory and IC feature reference: NXP NTAG213/215/216 datasheet, revision 3.2, 2 June 2015. This reference describes the IC, not the finished tag antenna or product rating.
Plan how the content will change
For content that changes frequently, encode a stable URL you control and update its destination content. Decide whether the tag will remain writable or be locked after verification. Treat permanent locking as a separate production approval step.
Separate access protection from authenticity
A password option is not the same as a complete product authentication system. A useful authenticity workflow also needs a defined threat model, appropriate chip capability, server verification where applicable, and careful provisioning.
Check the complete construction
Memory capacity does not establish the tag’s read performance. Antenna dimensions, application surface and phone antenna position still matter. For metal packaging, ask about an appropriate construction and test it on the actual material.
Choose the finished format
NTAG213 NFC labels suit a label specification; NTAG215 ISO cards provide a card format; NTAG216 RXK04 key fobs provide a carryable enclosure. Confirm the antenna, construction and reader interaction for the selected model.