Metal
A metal surface behind a standard inlay detunes the antenna and the tag stops reading. Tins, cans, foil pouches and metal cards need an on-metal tag with a ferrite isolation layer. This is the single most common failure we are asked to fix.
The technology, explained
What actually happens in that one second
A chip with no battery. A phone that powers it from a centimetre away. A web page that opens before you have put your hand back in your pocket. Here is the whole thing in plain English — and the handful of limitations nobody mentions until something does not read.
- No app, ever
- No battery in the tag
- 1–2 cm read range
13.56 MHzThe frequency every NFC phone speaks
The short answer
NFC — Near Field Communication — lets two devices exchange a small amount of data when they are within a couple of centimetres of each other. An NFC tag is a tiny chip attached to a coil of wire. It has no power source. When you bring a phone close, the phone emits a magnetic field; the coil harvests just enough energy from that field to wake the chip, which replies with the data it holds — usually a web address. The phone shows you a notification, you tap it, and the page opens in your browser. The whole exchange takes well under a second.
Step by step
One tap, five things happening
1
The phone is already listening
Any NFC-capable phone with the screen on is quietly emitting a short-range magnetic field, polling for a tag. You do not switch anything on — on iPhone and most Android handsets it is simply always ready.
2
The tag wakes up
Bring the tag inside that field and its antenna coil picks up energy by inductive coupling — the same physics as a wireless phone charger, at a far smaller scale. That harvested energy powers the chip for a fraction of a second.
3
The chip answers
The chip modulates the field to send back what it stores: an NDEF record containing a URL, plus a unique identifier burned in at the factory that cannot be changed.
4
The phone shows a notification
The operating system reads the record and displays a banner showing the destination. Nothing opens automatically — the person always chooses whether to continue, which is deliberate.
5
Your page loads
The link opens over HTTPS in the phone's normal browser. From there it behaves like any other web page: it can verify a product, show a profile, open a review form or take an RSVP.
Compatibility
Which phones can tap
The honest version: the large majority of phones in active use can read an NFC tag with no setup at all. A small minority need a free app or will use the QR fallback.
| Device | Reads NFC tags? | What the user does |
|---|---|---|
| iPhone XS, XR and newer (iOS 14+) | Yes — in the background | Unlock, hold the top of the phone to the tag, tap the banner. |
| iPhone 7, 8, X | Yes — with help | Use the NFC Tag Reader in Control Centre or a free reader app. |
| iPhone 6s and older | No tag reading | Use the printed QR code or the short URL. |
| Android with NFC (most mid-range and above, 2015 onward) | Yes — in the background | Hold the tag to the rear of the phone, tap the notification. |
| Entry-level Android without NFC hardware | No | Use the printed QR code or the short URL. |
| Tablets and laptops | Rarely | QR code or typed URL. |
Why we print a QR code on everything
NFC is faster and far harder to counterfeit; QR works on literally any phone with a camera. Treating them as rivals is a mistake. Every Capstone Tek product carries both, so the fast path is available to most people and nobody is ever locked out.
Limits & physics
The things that actually break a tap
Nearly every disappointing NFC deployment fails for one of these four reasons. All four are predictable, and all four are solved at the specification stage rather than after the print run.
Distance and placement
Real-world range is one to two centimetres. Put the tag where a hand naturally goes, and mark it — people do not guess. A small tap symbol doubles first-attempt success.
Phone cases and antenna position
Most slim cases are fine. Thick wallet cases with card slots or magnetic plates block the field. The antenna sits near the top rear on iPhone and higher-centre on most Android phones.
Tag size and chip choice
A bigger antenna reads from further away. A 25 mm disc on a wine neck behaves very differently from a credit-card-sized inlay. We match the chip — NTAG213, 215 or 216 — to the memory and range you need.
Security
What an NFC tag can and cannot be trusted with
Being straight about this matters more than selling it. NFC is secure for the jobs we use it for, and we do not use it for the jobs it is not suited to.
What makes it safe
- Range is the first defenceA tag cannot be read across a room or through a bag. Every read is a deliberate act within two centimetres.
- A unique identifier you cannot forgeThe UID is written during chip manufacture and is permanently read-only. Authentication checks it, not the printed artwork.
- Locked memoryWe write the link and then set the tag read-only, so nobody can overwrite your URL with their own.
- HTTPS at the other endThe destination is a TLS-secured page. The security of the experience lives there, where it can be maintained.
What we never do
- Store personal data on the tagThe chip holds a link and an identifier. Nothing about a person is ever written to it.
- Store payment credentialsContactless payment is a different, bank-controlled system. Our tags have nothing to do with it.
- Trigger anything automaticallyA tap only ever shows a notification. The person always decides whether to open it.
- Claim a tag cannot be copiedThe link on a tag can be copied onto another tag. That is exactly why authentication relies on the unlockable UID and your batch records instead.
Glossary
The words suppliers use
| Term | What it means in practice |
|---|---|
| NFC | Near Field Communication. Short-range wireless at 13.56 MHz, built into virtually every modern smartphone. |
| Tag / inlay | The chip plus its antenna. An inlay is the bare chip-and-antenna layer that gets laminated inside a card or label. |
| NTAG213 / 215 / 216 | The common NXP chip family. They differ mainly in memory: roughly 144, 504 and 888 usable bytes. A URL needs very little, so 213 suits most jobs. |
| UID | Unique identifier. A serial number written at the factory and permanently read-only — the anchor for authentication. |
| NDEF | The standard data format a phone understands. An NDEF record holding a URL is what makes a tag open a web page. |
| Encoding | Writing the NDEF record onto each tag. For us it also means recording which tag went on which product or card. |
| Locking | Permanently setting the tag read-only after encoding so the stored link cannot be altered. |
| On-metal tag | A tag with a ferrite layer that isolates the antenna from a metal surface so it still reads. |
| Tamper-evident tag | A tag whose antenna is destroyed if the label is peeled, so a removed tag stops working. |
| Passive tag | A tag with no battery, powered entirely by the reading device. All our tags are passive. |
Where it came from
Twenty years of groundwork, then suddenly everywhere
NFC feels new because the moment it became useful for marketing was recent. The technology itself is middle-aged.
1
RFID matures
Contactless identification is standard in logistics, access control and transit long before any phone has it.
2
NFC is standardised
A short-range, two-way branch of RFID at 13.56 MHz, defined specifically for consumer devices.
3
Android adopts it
NFC becomes common on Android handsets, mostly in service of contactless payment.
4
Apple opens it up
Background tag reading arrives on iPhone, and the addressable audience roughly doubles overnight.
5
It becomes ordinary
Tapping to pay teaches everybody the gesture. Tapping a product, a card or an invitation now needs no instruction.
Why that last step mattered most
The barrier was never the chip, which has cost pennies for years. It was the gesture. Contactless payment trained hundreds of millions of people to hold a phone against a thing and expect something to happen — and the moment that became instinctive, every other use of NFC stopped needing an explanation.
Chip selection
Which chip goes in your product
Memory matters less than people expect, because a tag should hold a link rather than content. Antenna size and construction matter far more.
| Chip | Usable memory | Typical use | When we pick it |
|---|---|---|---|
| NTAG213 | ~144 bytes | Labels, cards, review stands, invitations | The default. A URL needs a fraction of this, and it is the most economical at volume. |
| NTAG215 | ~504 bytes | Multi-record tags, certain gaming and toy ecosystems | When several NDEF records must live on the tag itself rather than behind the link. |
| NTAG216 | ~888 bytes | Specialist applications | Rarely. Only when a genuinely large payload must be readable offline. |
| On-metal variants | Same as base chip | Tins, cans, foil, metal cards, equipment | Whenever the mounting surface is metal or metallised. Non-negotiable — a standard tag will not read. |
| Tamper-evident | Same as base chip | Seals, caps, high-value authentication | When the tag must stop working if it is peeled off and moved to another item. |
| Washable / textile | Same as base chip | Garments, soft goods, care labels | When the tag has to survive laundering and mechanical stress. |
Designing the tap point
People do not search a package for an invisible chip
The most expensive mistake in NFC is a perfectly working tag nobody knows is there. Six rules we apply to every project.
Mark the spotA small tap symbol and two or three words. "Tap to verify", "Tap to review", "Tap for details". It roughly doubles first-attempt success.
Put it where a hand already goesThe neck of a bottle, the front of a counter card, the centre of a business card. Not the underside of a base.
Print the fallback nearbyA QR code and a short typed URL in the same visual block, so nobody has to hunt for plan B.
Account for what is behind itMetal, foil and dense liquid change the behaviour. Test against the real packaging, not a flat sample.
Size the antenna for the jobA larger antenna reads from further away and finds the phone faster. Shrink it only when the format forces you to.
Make the reward obvious"Tap here" is a weak instruction. "Tap to see if this is genuine" tells people why they should bother.
Testing
How to check a deployment before it ships
We run all of this before delivery, but it is worth knowing what good testing looks like — not least so you can hold any supplier to it.
01
Both platforms
One recent iPhone and one mid-range Android, because the notification behaviour and browser handoff differ between them.
02
In a case
Test with a phone in a typical case, not a bare handset. A thick wallet case is the realistic worst scenario.
03
On the real surface
Mounted on the actual product or card, not loose on a desk. This is where metal and foil problems surface.
04
Signed out
Open the destination on a phone that is not signed in to anything. The signed-out journey is always longer than you remember.
05
The fallback too
Scan the QR code and type the short URL by hand. Both must land in exactly the same place.
Accessibility
A tap is easier than a scan, for most people
This is an underrated advantage. Scanning a QR code requires holding a camera steady, aiming at a small target and seeing well enough to frame it. Tapping requires putting one object against another.
For someone with a tremor, limited dexterity, low vision or simply a full pair of hands, that difference is substantial. It is also why we insist the destination page itself is built properly — large tap targets, real text rather than text in images, sensible contrast, and a layout that survives being zoomed.
- No aiming requiredContact, not camera framing — far more forgiving of unsteady hands and poor light.
- Readable destinationsProper semantic HTML, so screen readers and reader modes handle the page correctly.
- Always a second routeQR and a typed URL, because the right answer for one person is the wrong one for another.
The environmental picture, honestly
An NFC tag is a small piece of aluminium or copper and a speck of silicon on a plastic film. That is not nothing. The case for it rests entirely on replacement: one reusable card instead of repeated print runs, or one tag that removes a multilingual leaflet from every carton.
What we do about it
Paper-faced labels rather than PET where the application allows, bamboo and recycled-PET cards for those who want them, plastic-free packing, and a straight answer when your volumes are too low for the switch to make any genuine difference.
Technical FAQ
Short answers to technical questions
More of them, including commercial questions, on the main FAQ page.
Got an awkward surface?
Metal, foil, curved glass, fabric or something unusual — send us a sample and we will test it rather than guess.
Send us a sampleAbout four centimetres in theory and roughly one to two centimetres in practice. That short range is a security feature: a tag cannot be read across a room or from a passing bag, so a tap is always deliberate.
No. An NFC tag is passive. The reading phone generates a small magnetic field, the tag's antenna harvests enough energy from it to power the chip, and the chip replies. A tag has no battery, nothing to charge and no meaningful shelf-life limit.
iPhone XS and newer read tags in the background on iOS 14 and later; iPhone 7 to X read tags through the Shortcuts app or a reader app. Almost every Android phone above entry level from the last several years reads tags natively. In practice the large majority of smartphones in use today can tap.
The tag itself holds only a link and an identifier, never payment data or passwords. The security sits in three places: the short read range, the chip's permanently locked unique identifier, and the HTTPS page the link opens. For authentication we also lock the tag memory so the stored link cannot be rewritten.
NFC is a specific, short-range branch of RFID that operates at 13.56 MHz and allows two-way communication. The practical difference is that every modern smartphone is an NFC reader, while general RFID needs dedicated reader hardware.
Through most plastic, leather and silicone cases, yes. Thick wallet cases with card slots and metal plates can block it. Mounting a standard tag directly on metal detunes the antenna, which is why we use on-metal tags with a ferrite layer for tins, cans and metal cards.
Put it to work
Start here
Tell us what you want a tap to do
One short call is usually enough to scope it. We will come back with a plan, a sample and a fixed price — normally within one business day.