NFC Tag
An NFC tag is a small chip and antenna that stores a short piece of data, usually a URL, and transmits it to a phone held within a few centimetres. NFC stands for Near Field Communication. The tag has no battery: the phone’s radio field powers the chip through inductive coupling, which is why a sticker the thickness of paper can work for years.
Why NFC Tags Matter
NFC tags remove the aiming step. A tap works in the dark, at an angle, through a phone case, and without opening the camera. That matters on a bar table, a museum placard, or a product itself.
Programmable NTAG213 stickers cost roughly $0.20 to $0.50 each in modest volumes, against effectively zero for a printed code. The tag wins where the interaction repeats or the surface is premium. Print wins where volume is high and margins are thin.
The tradeoff is discoverability. A QR code announces itself. An NFC tag is invisible, so it needs a printed prompt and the universal tap symbol, or nobody touches it.
How Do NFC Tags Work
NFC runs at 13.56 MHz over a practical range of about 4 cm, with the specification allowing up to 10 cm. Data moves at 106, 212, or 424 kbit/s.
The sequence on every tap:
- The phone emits a 13.56 MHz field whenever its NFC radio is active.
- The field induces current in the tag’s antenna coil, powering the chip. No battery is involved.
- The chip returns its stored data by modulating the load on that field.
- The phone parses the data as NDEF, the NFC Data Exchange Format standardised by the NFC Forum.
- The operating system acts on the record, typically opening a URL.
A URL is stored as an NDEF URI record with a one-byte prefix code standing in for the common scheme, which saves memory:
Prefix byte 0x04 = https://
Payload = linkutm.com/spring?utm_source=shelf-tag
Tag stores = 0x04 + "linkutm.com/spring?utm_source=shelf-tag"
The NFC Forum, founded in 2004 by Nokia, Philips, and Sony, defines these formats. Android has read NDEF tags in the background since Android 4.0. On iPhone, background reading arrived with the XR and XS on iOS 13; earlier NFC-capable iPhones need the Tag Reader in Control Center.
NFC Tag Types
The NFC Forum defines five tag types, separated by the underlying standard, memory, and speed.
| Type | Based on | Typical memory | Speed | Common use |
|---|---|---|---|---|
| Type 1 | ISO/IEC 14443A (Topaz) | 96 bytes to 2 KB | 106 kbit/s | Largely legacy |
| Type 2 | ISO/IEC 14443A (NTAG, MIFARE Ultralight) | 48 bytes to 2 KB | 106 kbit/s | Marketing tags, posters, stickers |
| Type 3 | JIS X 6319-4 (FeliCa) | Up to 1 MB | 212 or 424 kbit/s | Transit and payment, mostly Japan |
| Type 4 | ISO/IEC 14443 A/B (DESFire) | Up to 32 KB | 106 to 424 kbit/s | Access control, authentication |
| Type 5 | ISO/IEC 15693 (NFC-V) | Up to 8 KB | 106 kbit/s | Longer range, inventory and labels |
Type 2 covers almost all marketing use. The NTAG family sets the practical limits: NTAG213 holds 144 bytes of user memory, NTAG215 holds 504, and NTAG216 holds 888.
That 144-byte figure matters more than it looks. A campaign URL with five UTM parameters can run past 130 characters, which is the usual reason a cheap tag rejects a write.
NFC Tag vs QR Code
Both open a URL. They fail in different ways, so the choice is about context rather than which is better.
| NFC tag | QR code | |
|---|---|---|
| Action | Tap | Point the camera |
| Works in the dark | Yes | No |
| Distance | About 4 cm | Any, if printed large enough |
| Unit cost | $0.20 to $0.50 | Near zero to print |
| Device support | Most modern phones, not all budget Androids | Any camera phone |
| Editable after deployment | Yes, unless locked | Only if dynamic |
| Damage tolerance | None. A cracked chip is dead | Reed-Solomon correction survives 7% to 30% loss |
| Discoverability | Needs a printed prompt | Self-evident |
Reach favours the QR code, since every camera phone reads one and nothing has to be manufactured. NFC favours repeat interaction, premium surfaces, and situations where pulling up a camera is awkward.
Running both on one asset is common and costs little. Print the code, embed the tag behind it, and give each a different campaign value so the reports stay separable.
How to Program an NFC Tag
Writing a tag takes a phone and a free app such as NXP TagWriter or NFC Tools.
- Buy the right chip. NTAG213 suits most campaigns. Choose an on-metal tag with ferrite shielding if the surface is metallic.
- Prepare the URL first. Shorten it before writing, since memory is the binding constraint.
- Write an NDEF URI record. Select the URL or URI record type in the app, paste the address, and hold the phone against the tag.
- Test on both platforms. Android and iOS handle prompts differently.
- Lock the tag. Locking is permanent and makes the tag read-only. An unlocked tag in public can be rewritten by anyone with a phone.
Tracking is the step most people skip. An NFC tag records nothing, so taps are invisible unless the URL carries the measurement. Write a tracked short link and the tap is logged before the redirect, so link analytics report taps by location and device. A short link also fits inside 144 bytes with room to spare.
Common NFC Tag Problems
- Metal detunes the antenna. Mounting a standard tag on metal kills the read. On-metal tags include a ferrite layer to correct for it.
- The tag was never locked. Anyone can overwrite an unlocked public tag and redirect it.
- No prompt on the surface. Without a visible tap symbol the tag is invisible.
- Antenna position varies. The NFC coil sits at the top on most iPhones and near the centre on many Android handsets.
Frequently Asked Questions
What is an NFC tag?
An NFC tag is an unpowered chip and antenna that stores a small amount of data, usually a URL, and transmits it to a phone tapped against it. The phone’s own radio field powers the chip, so no battery is needed. Most marketing tags are NFC Forum Type 2 chips such as the NTAG213.
Do NFC tags need a battery or internet connection?
NFC tags need neither. The chip draws power from the reading phone’s 13.56 MHz field through inductive coupling, and the data it returns is stored on the chip itself. Internet access is only needed afterwards, when the phone opens the URL the tag handed it.
Is an NFC tag more secure than a QR code?
Neither is inherently secure, since both just hand over a URL. NFC’s short range makes remote interception impractical, but an unlocked tag can be rewritten by any passerby, and a sticker can be placed over either one. Locking the tag after writing closes the main gap.
Can you reprogram an NFC tag?
Yes, as long as it was not locked. Rewriting an NDEF record replaces the stored data, so the same tag can point somewhere new without reprinting anything. Locking is a one-way operation, so a tag made read-only stays that way permanently.
To write a tracked short link to your NFC tags and see taps by location and device, build the link at linkutm.