Phone call QR code

When to use it

Emergency contact labels on lifts and machinery, “call to book” on a shop window, a taxi firm’s card, the support line in a manual, a property agent’s sign. A phone code removes the two most common failures with printed numbers: misreading a digit and mistyping it.

How it behaves on phones

iPhone: the Camera app shows a banner with the number. Tapping it opens the Phone app with the number ready, and a further tap makes the call.

Android: most Android scanners show the number with a “Call” button and open the dialler. Google Lens does the same. On a tablet without a SIM the number is offered for copying instead.

Gotchas

International format. Start with +, then the country code, then the number with the leading trunk zero dropped. A UK number written locally as 020 7946 0100 becomes tel:+442079460100. Every phone on earth knows how to dial that.

No spaces. Some scanners cope with spaces, some stop reading at the first one. Leave them out.

Extensions and pauses. A comma inserts a two second pause on most phones, so tel:+15550100,,204 dials, waits, then sends the extension. It is not universal, and iPhone treats ; differently from ,. Print the extension in text too.

Free numbers abroad. A toll free number often does not connect from another country. If your callers travel, give a geographic number.

Size. tel:+15550100 is 13 characters and fits version 1, the smallest QR code, 21 modules on a side. That means it prints very small and still scans.

Print advice

Level M, or H if the code is a small sticker on equipment that gets scuffed. Because the payload is tiny, a version 1 code at level H is still only 21 modules and a 2 cm sticker works well. Print the number in plain text beside it. In an emergency, someone with a cracked camera lens needs to be able to dial by hand.