GUIDE
How to Program an NFC Keychain With Your Phone
Write a link, contact card, or Wi-Fi login to your NFCKEY in under a minute, straight from your phone.
How it works
An NFC keychain works like a contactless card, except you decide what's stored on it. Tap it against a phone and whatever's written there opens automatically: a website, a contact card, a Wi-Fi login.
What gets written is called an NDEF record, the same standard format used by contactless cards everywhere, so it's readable by any NFC phone, not only the one that wrote it.
steps to write one
Install a writing app
Free, one-time install. Which app depends on your chip.
Choose what happens on tap
A link, a contact card, a Wi-Fi login, or plain text.
Hold your phone to the keychain
A few seconds against the back of the phone writes it.
Rewrite anytime
Nothing is used up. Repeat to change it later.
What businesses encode, and why
The record type follows from the job. These come up most often across NFCKEY orders.
Find the guide for your chip
Step-by-step programming instructions live in two guides, one for each chip technology NFCKEY is built on. Match your chip family below to find the one that applies to your order.
NXP chip families
iPhone · Android
Programmed with the NXP TagWriter app.
ST25 chip family
iPhone · Android
Programmed with the ST25 NFC Tap app.
Needs formatting before it can be encoded by phone: ICODE and ST25TV16KC. Once formatted, each writes with its usual app, NXP TagWriter for ICODE, ST25 NFC Tap for ST25TV16KC.
Cannot be encoded with a phone app: MIFARE Classic, MIFARE DESFire, MIFARE DUOX, MIFARE Plus, and JCOP. These are secure chip lines built around key authentication for access-control and payment deployments, and need a dedicated encoder or system-level provisioning rather than a consumer app.
Don't know your chip?
Check your order confirmation email, which lists the chip family selected at checkout. Still unsure? Email inbox@nfckey.com with your order number.
Frequently asked questions.
No. The phone needs a writing app installed to build the record. Which app depends on the chip family, covered in the guide picker above.
For most chip families, no. Any NFC-enabled phone can write to an NFCKEY using a free app, NXP® TagWriter or ST25 NFC Tap depending on the chip. A few secure chip lines (MIFARE® Classic, MIFARE® DESFire®, MIFARE® DUOX, MIFARE® Plus, and JCOP®) are the exception, these are built for access-control and payment use, and need a dedicated encoder or system-level provisioning instead.
No. NFC only works at a range of a few centimeters. A reader has to be held directly against the keychain to get any response at all.
No. The record can be rewritten at any time with the same app, unless the chip has been deliberately locked to prevent further writes.
Chips ship blank by default, ready for you to encode. Pre-encoding to your specification before shipment is available on request, including UID-to-print mapping for traceability.
Start from the readers or systems you're integrating with. If you just need a simple phone-programmable tag, NTAG®, MIFARE® Ultralight, ST25TA64K, or ST25TN01K all write directly from a free app. If your deployment needs cryptographic security, for access control or payments, MIFARE® Classic, MIFARE® DESFire®, MIFARE® DUOX, MIFARE® Plus, or JCOP® may fit better, but these need a dedicated encoder rather than a consumer app, so plan your programming workflow around that.
Between 48 bytes and 16 K depending on the chip. A web address fits comfortably on the smallest option in the range; a full contact card needs more headroom.
Confirm NFC is enabled in phone settings, remove any thick case, and hold the keychain steady against the upper back of the phone for a few seconds rather than tapping quickly.
