How close does the phone need to be?
Close enough to touch. Hold the phone against the tile, or within a centimetre or two.
You will see different numbers, because they measure different things:
| Source | Figure | What it describes |
|---|---|---|
| NFC Forum | Up to about 2 cm | Typical range. Its certification tests a compliant range of 5 mm. |
| Android | 4 cm or less | Typical distance needed to start a connection. |
| NXP chip datasheet | Up to 10 cm | The chip's maximum, depending on field strength and antenna. It is not a phone figure, so don't plan around it. |
Why there is no battery
The phone's radio field supplies both the energy and the data link. The chip only needs its antenna coil. That is why a tile can be thin enough to stick to a table, and why there is nothing to charge.
It also means a tag cannot do anything on its own. If a phone has no NFC, or NFC is off, nothing happens and no message appears.
What fits on a chip
Less than you would think, and it is enough. The common chips for this job are NXP's NTAG family:
| Chip | User memory |
|---|---|
| NTAG213 | 144 bytes |
| NTAG215 | 504 bytes |
| NTAG216 | 888 bytes |
The smallest holds a web link of roughly 130 characters, which is plenty for a short address. A venue does not need a bigger chip to hold a longer menu, because the menu is not on the chip. Only the link is.
A phone needs no app to open that link, as long as the chip stores it in the standard format, called an NDEF URI record. iPhones read web addresses starting http or https, and do not support custom link types.
Can the link be changed?
An NTAG chip can be rewritten until it is locked. Locking is permanent: it cannot be undone. Password protection is the other option.
That gives a venue a real choice:
- Leave it unlocked, and someone with a phone and a free app may be able to rewrite it.
- Lock it to your final link, and it is safe, but it can never point anywhere else.
- Lock it to a stable link, and change where that link leads whenever you need to. Someone has to keep that link running.
The third is the most flexible. Ask who controls that link before you buy. Our buying checklist covers this.
How long does a chip last?
NXP specifies at least 10 years of data retention and at least 100,000 write cycles, both at 22 °C. That is the chip's memory only. The glue, antenna and casing of a finished product are separate, so a chip figure is not a promise about a tile on a busy table.
What does a tap share?
Reading a tag moves data one way, from the tag to the phone. The tag has no network connection and doesn't collect a guest's name or number, so the tap alone tells the venue nothing about the person.
The page that opens is an ordinary website. Like any website, it can use cookies and analytics, and can learn things like the device and browser type. If a guest signs in to Google to leave a review, that goes through Google.
What stops it working
Mostly metal, phone settings and thick cases. See NFC tag not working? for the checks, in order.