Phone QR codes — how they work

A phone QR code stores a tel: URI. Scanning it opens the dialler with the number entered, ready to call — it never dials on its own. Always store the number in full international format (+country code) so it works for people roaming or calling from abroad.

The payload

tel:+14155552671

That is the whole thing — RFC 3966. UseQR normalises what you type, stripping spaces, brackets and dashes, because scanners disagree about which separators they tolerate.

Always use international format

A number stored as 020 7946 0958 works only for someone already in the UK national dialling context. Stored as +442079460958, it works from anywhere and while roaming. The + is meaningful: it tells the dialler to substitute the correct international access prefix for wherever the phone currently is.

This is not a theoretical concern. A hotel, a taxi rank, a tourist site — anywhere the scanner might be a visitor with a foreign SIM — a national-format number simply fails.

What happens on non-phones

Tablets without cellular: iPads offer FaceTime Audio or hand the call to a paired iPhone. Android tablets usually show the number with no action.
Desktop scanners: macOS offers to call via a paired iPhone; Windows generally copies the number.
Some browsers show a confirmation dialog before opening the dialler.

None of these fail badly, but if the surface will mostly be scanned on a laptop, print the number in text next to the code as well.

Extensions

Extensions are unreliable. The syntax tel:+14155552671;ext=42 is standardised but support varies, and pause characters (, or p) inserted into DTMF sequences behave differently across Android manufacturers. If you need an extension, print it as text and let the caller enter it.

FAQ

Does a phone QR code dial automatically?

No. It opens the dialler with the number filled in; the user presses call. No QR code can place a call by itself.

What format should the number be in?

Full international format with a leading plus, for example +14155552671. National-format numbers fail for anyone scanning from another country or while roaming.

Do extensions work?

Inconsistently. The tel: URI supports an ext parameter but handset support varies widely. Print the extension as visible text instead.

What happens if someone scans it on a tablet?

Cellular-less tablets typically offer an internet-calling option or just display the number. It degrades gracefully, but print the number in text if desktop scanning is likely.