# 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.

Source: https://useqr.app/phone-qr-code · Last reviewed 2026-08-21 · UseQR is free forever, MIT licensed, no signup.

---

## 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.

## Try it

- https://useqr.app/phone
- https://useqr.app/sms
- https://useqr.app/whatsapp