How NFC technology actually works
NFC is a radio technology that only works over a very short distance. The surprising part is that passive tags have no battery: the magnetic field produced by the reading phone also supplies the power that wakes the chip inside the card.
The field carries the power, the data rides on it
The phone generates a field at 13.56 MHz. The antenna inside the tag harvests energy from that field by induction, the chip wakes up and sends back whatever it stores. That's why an NFC sticker still works after years in a drawer — there's no battery inside to run flat.
NDEF: the shared data language
For phones to understand each other, the data needs a common format, and that format is NDEF. An NDEF record can carry text, a URL or a MIME type. For a business card, the typical payload is a contact record with the `text/vcard` type; when the phone sees it, it offers to save the contact directly.
HCE: the phone impersonating a card
Host Card Emulation lets a phone behave as if it were an NFC tag. The app answers the reader in the background and the same data moves across with no physical card involved. That's exactly what Business Card Tap does: it presents the phone as a Type 4 tag and delivers the vCard. (This is an Android capability; Apple doesn't open this kind of card emulation to third-party apps.)
Frequently asked questions
How is NFC different from Bluetooth?
NFC needs no pairing and is limited to centimetres; Bluetooth has long range but requires a connection step. NFC is sometimes used just to kick off a Bluetooth pairing.
How much data fits on an NFC tag?
Common tags hold anywhere from 144 bytes to a few kilobytes. That's usually enough for a contact record; for anything long, writing a link is the safer choice.
Does it work while the phone is locked?
On the reading side, most phones need the screen on. For card emulation the behaviour varies by device, but generally the screen must be on and the phone unlocked.
Does an NFC tag need a battery or power source?
No — passive NFC tags, the kind used in cards, are powered entirely by the reader's electromagnetic field during the tap. That's why a card can sit in a drawer for years and still work the moment it's read.
What frequency does NFC operate on?
NFC runs at 13.56 MHz, the same band used by many contactless payment cards and access badges. That shared standard is part of why phones can read such a wide range of tags.
Can NFC tags be read through wallets, cases, or clothing?
Usually yes, within a few millimetres — NFC's radio waves pass through thin non-metal materials like leather, fabric or plastic without much loss. Thick materials or anything with metal in it can block the signal.
What's the difference between common NFC tag types like NTAG213, 215 and 216?
They're mostly the same technology at different memory sizes — 213 holds around 144 bytes, 215 about 504, and 216 around 888. More memory means you can store a longer link or a full contact record instead of just a short URL.
Can an NFC tag be cloned or copied?
Basic tags with no security features can be copied fairly easily with the right reader/writer. Tags with a locked memory area or authentication keys are much harder to duplicate, which matters more for access control than for a simple business card.
Does NFC require an internet connection to work?
The tap itself doesn't — reading or writing the tag's memory happens locally between the phone and the chip. An internet connection is only needed afterward, if the tag points to a web link that needs to load.
How many times can an NFC tag be rewritten?
Typical tags are rated for around 100,000 write cycles, far more than a business card will ever need. What eventually limits reuse is usually physical wear on the card, not the chip's memory.
Can metal surfaces interfere with NFC reading?
Yes — metal reflects and absorbs the reader's magnetic field, which can shrink the effective read range or block it entirely. Metal business card holders or phone cases with a metal plate are common culprits.
What happens if two NFC tags are placed too close together?
The phone can get confused about which tag to read, sometimes failing to read either one — this is sometimes called tag collision. Keeping tags at least a couple of centimetres apart avoids the problem.
Is NFC data encrypted by default?
No — a standard NFC tag's data is readable by any phone that taps it, the same way a QR code is readable by anyone who scans it. Encryption and access control exist for NFC, but they need to be set up specifically; they're not the default for a basic tag.
Turn your phone into your business card. Business Card Tap sends your details to another phone with a tap over NFC, and falls back to an on-screen QR code when NFC isn't available. Fully offline, no account.
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