How do you write a contact card to a tag?
A contact record carries a vCard as a MIME typed payload, which a phone offers to save when the tag is tapped. It works with no network, it is considerably larger than a URL, and it fixes your details permanently unless you rewrite every tag.
How the record works
The payload is a vCard, the same format an address book exports, carried in a record typed as MIME media so the phone knows to treat it as contact data rather than as text.
A writing tool presents fields to fill in and builds the vCard for you. Tapping the tag then offers to add the contact, without any application involved beyond the address book.
Size is the constraint
A vCard is verbose. Field names, structure and line endings all cost bytes before your actual details, and a complete card with a name, two numbers, an email, a company and an address quickly outgrows the smallest tags.
Two consequences follow. Check free space before writing rather than after, and be selective about fields: a photograph in a vCard is out of the question, and a long postal address may be one field too many.
The pragmatic middle
Write only what someone needs to reach you: name, one number, one email. Everything else belongs on a page you link to, where it also stays correctable.
The advantage that justifies it
It works with no network. This is the entire case for a vCard over a link, and it is a strong one in the situations where business cards are actually exchanged: a basement conference venue, a car park, a trade hall with saturated coverage.
A link fails silently in those places. The tag reads, the browser opens, and nothing loads. A vCard hands the details over regardless.
The cost nobody plans for
Your details are now in the tag. Change your phone number, your email or your job title, and every card you handed out carries the old one, with no way to correct them.
Every card you still hold can be rewritten, which is why locking a contact tag is almost always a mistake. The ones already given away cannot.
This is the trade in one sentence: a vCard works everywhere and never changes, a link changes freely and needs a network. Which matters more depends on where your cards get handed over, and that is a question worth answering before ordering a hundred.
Frequently asked questions
Can I include a photo in the vCard?
Not realistically. Even a small image is far larger than the memory available on a normal tag, and this is one of the clearest cases where a link to a page is the only workable route.
Does a vCard tag work on both Android and iPhone?
Contact data is one of the better supported record types on both, and behaviour still differs in how the save prompt appears. Test on both before producing a batch.
Should I lock a contact tag?
Almost never. Contact details change more often than people expect, and locking removes the only remedy you have for the cards still in your possession.
Is a vCard better than a link for a business card?
It depends on where the card is handed over. Offline reliability favours the vCard, updatability favours the link, and there is no answer that is right in both situations.