Tags that work with Hex NFC

A sticker from a pack of blanks, a hotel key card and a library label all feel the same in your hand. The chip inside them is not the same, and it decides how much the tag holds and whether it can take a password.

For tags of your own, buy blanks from the NTAG family. An NTAG213 holds 144 bytes, enough for a web address or a short contact. An NTAG215 holds 504 bytes and an NTAG216 holds 888, which is what a long note or a stack of records needs. Each of the three can take a password and can be locked. A tag you did not buy blank is usually filled with data only whoever issued it can make sense of. A hotel key, a transport card and a building pass are all that kind of tag.

To find out what a tag in your hand is, scan it. What the app read opens on the Tag screen. The card at the top of that screen is the tag info card, headed with the chip's own name. Scan a tag walks through the scan itself.

The name is a part number, so it is the thing to search for when you want to know what a tag can take. Chip by chip, what the app does with each one is set out in the Chip support matrix. That page is part of the developer documentation rather than this guide, so it talks about commands and test runs.

The names the app shows

The heading of the tag info card is the chip's own name. These are the names it can show.

The last row is what you see when the chip answers as one of a family but will not say which model it is. A Japanese transit card reads as FeliCa and opens its own result, covered in Read a transit card. A passport reads as ePassport, covered in Read a passport.

Some chips say nothing an NFC app can match against a part number. The card then carries a Reported row and a Version bytes row in place of a name, which are the tag's own words about itself. Such a tag can still be read and written as an ordinary tag. What it loses is everything that depends on knowing the chip's memory layout. That rules out a password, a permanent lock and Memory dump, the operation Save a copy of a tag's memory explains.

What the card says about the silicon

Two rows summarise the chip. Supports lists what the app can do with it, such as "Read", "Write", "Password" or "Lock". "Write" means the tag takes a new message, as in Write a link to a tag. "Password" means it can carry one of its own, covered in Protect a tag with a password. "Lock" means the tag can be made read-only. That cannot be undone on any tag, which is why Lock a tag permanently is a page of its own. Features lists the extras the silicon carries, such as "Tap counter" or "Tamper loop".

Under those sit rows that only appear when the chip answered for them. A row that is missing means the chip said nothing about it, never that the scan went wrong.

A Tamper row belongs to a chip with a tamper loop, which today means an NTAG213 TT. It reads "Seal intact" while the loop is whole, and "Opened" once the loop has been broken. A broken loop stays broken. A seal the app reports as open was already open when you found the tag. No scan of yours broke it.

A Times read row comes from a chip with a tap counter, and holds the number of reads the chip has counted. "Counter off" is different from a missing row: the counter is there and switched off, which is how most tags leave the factory.

A Counters row comes from a MIFARE Ultralight EV1, in either of its two sizes. That chip keeps three counters of its own, and the row holds all three on one line. A second Counters row reading "Tearing event detected" means the chip reports that those counters are not intact. A MIFARE Ultralight C shows neither row, because its counter answers a command the app does not send.

A Signature row reads "NXP originality signature" when the chip answered with a 32-byte signature. It reads "Not a standard NXP signature" when the answer was shorter than that. Neither line is a verdict on whether a tag is genuine. The app writes down what the chip replied, and checks it against nothing.

What an iPhone cannot read

One common card is out of reach on any iPhone. A MIFARE Classic stops the scan with a message saying so: the tag is not faulty, and no NFC app on iOS gets further. Why can my iPhone not read this tag at all? has the message and the reason.

A MIFARE DESFire card is a softer version of the same limit. The app names the card and can send raw commands to it, and it reads records only when the card carries an ordinary NDEF area. The rest of a DESFire sits behind keys held by whoever issued the card.

If a tag you believe is supported still will not scan, the cause is usually the hold rather than the chip. See If a tag does not scan or write.