NFC Pet Tags: Store Owner Contact, Vet Info, and the Microchip Number

Write an NFC tag with your contact details, clip it to your pet's collar, and anyone who finds your dog or cat can tap a phone to it and reach you in seconds — no app, no account, no call to a registry. One thing to be clear about first: a collar tag works alongside the implanted microchip, not instead of it.

Quick answer: a supplement, not a replacement

The microchip your vet implanted and an NFC collar tag are two technologies for different halves of the problem. The implant runs at 134.2 kHz under ISO 11784/11785 and stores only a 15-digit ID a shelter scans with a dedicated reader and looks up in a registry. A normal phone can't read that implant; the frequency is far below NFC's 13.56 MHz.

An NFC collar tag is the opposite. It's an NFC Forum Type 2 tag any modern phone reads by tapping, so the neighbor who finds your cat gets your number immediately. But a collar can slip off, which is why the implant stays the permanent backup. Use both — the tag for a finder with a phone, the chip and a current registry entry for the shelter.

What to put on the tag

You have three useful payloads, written as NDEF records:

• A URL record pointing to a found-pet page you host. You can edit that page anytime — new phone number, "I'm lost, please call" status — without rewriting the tag. A 144-byte NTAG213 holds this easily.
• A vCard record. The vCard format (RFC 6350) saves your name, phone, and your vet's number straight into the finder's contacts, and it works with no internet. A 504-byte NTAG215 fits a full card comfortably — the same approach as an NFC business card.
• A text record with the microchip number and registry name. Handy for a vet's reference, but it's plain text for a human to read — a phone still can't query the implant from it.

Set it up, step by step

1. Pick a chip. NTAG213 if you only need a URL; NTAG215 if you want a vCard or a longer note.
2. Write the payload. Open your NFC writer, choose URL, Contact, or Text, enter the value, and hold the tag to the phone. Our write guide covers the gotchas.
3. Test the tap. iPhone XS and later read tags in the background, so a tap on the top edge is enough; on Android a URL record opens on its own when the screen is unlocked.
4. Mount it for outdoor life. A collar lives in rain and sun, so skip the paper sticker — a waterproof PVC, epoxy-dome, or IP-rated hard tag lasts far longer. Our tag-sticker guide breaks down materials.
5. Lock it once you're happy, so a curious tap can't overwrite it.

Common problems and fixes

If a tap does nothing, you're usually off-target — move the tag to where the phone's antenna sits (top edge on iPhone, upper back on most Android). A tag that won't accept new data is probably locked, which is read-only by design. Mounted next to a metal ID disc, the metal detunes the antenna; an on-metal, ferrite-backed tag fixes that. And again: don't expect any phone to scan the implant — that's a job for a vet's 134.2 kHz reader.

Doing this on NFCore specifically

In NFCore, the Write Data screen handles all three jobs: pick URL for a hosted page, Contact for a vCard, or Text for the microchip number, type the value, and hold the tag to write. Templates saves a layout you can reuse if you're tagging more than one animal, and the tag inspector shows how many bytes you've used and whether the tag is still writable. NFCore doesn't track you or require an account. It's free on the App Store and Google Play.

FAQ

Does an NFC tag replace my pet's microchip?

No. The implant is the permanent ID a shelter scans and looks up in a registry; the NFC collar tag is a faster path for a finder who has a phone. Keep both, and keep your registry details current.

Can my phone scan my pet's implanted microchip?

No. Implants use 134.2 kHz RFID, which is far below NFC's 13.56 MHz, so it takes a dedicated ISO 11784/11785 scanner like your vet or shelter uses.

What if the finder's phone has NFC off?

Most modern phones keep NFC on by default, and iPhones read tags in the background. As a fallback, print a short "tap or call" line and your number on the collar too.

Which chip should I buy?

NTAG213 is enough for a URL. Choose NTAG215 if you want a vCard with owner and vet contact saved in one tap.