A WhatsApp QR code for your business

By Tiehl Roberto Matías · 6 min read · Updated 27 October 2026

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The WhatsApp QR is the one printed most and the one that goes wrong most, for a silly reason: the number has to be written in a very particular way, with no plus sign, no spaces and with the country code. And there is a second detail almost nobody measures: the pre-written message is paid for in module size.

The number, where everybody goes wrong

The WhatsApp link has this shape:

https://wa.me/5493735401234

That number at the end is the only thing you have to get right, and it has three rules with no exceptions:

• With the country code, always. Even if all your customers are from the same town. Without it, WhatsApp does not know whose chat to open.
• No + sign, no spaces, no dashes and no brackets. Digits only, all run together.
• No trunk zero. The zero dialled inside the country does not belong in the international format.

Some countries add a digit between the country code and the area code for mobiles — Argentina puts a 9 there, the same 9 used when calling from abroad. A Chaco number dialled locally as 0 3735 15 401234 is written 5493735401234 in the link. Check what your own country does before printing fifty of anything.

The pre-written message and what it costs

WhatsApp lets you leave a message already written in the customer's box, so all they have to do is hit send. It is convenient, but it is not free: every character of that message goes inside the code, and the code grows.

And it grows more than it looks, because spaces, accents and punctuation are each encoded with several characters. A space takes three. An ó takes six.

This is what this site's encoder measures, for a 90 mm piece at correction H:

What the link carries	Characters	Version	Module
The number only	27	4	2.20 mm
One-word message	37	5	2.00 mm
One-sentence message	71	8	1.58 mm
Two-sentence message	123	11	1.30 mm

Look at the jump: going from the number alone to an ordinary sentence shrinks the module by 28 %. With a 0.6 mm nozzle, which needs 1.2 mm modules, it still fits. With a 0.8 mm one, which needs 1.6 mm, the sentence no longer fits on a 90 mm piece.

What to put in the message

Given the above, the recommendation is clear: a short message or none at all.

What does justify the cost is a message that helps you tell where the customer came from. If you have codes in several places, a different message in each tells you instantly where they are writing from, without asking:

• «Table 4»
• «Enquiry from the shop»
• «Saw the sign»

Three words cost one version of code; a polite sentence costs four and adds nothing the customer was not going to type anyway. If in doubt, leave just the number: the customer writes whatever they like and the code comes out with large modules.

The text that is worth having is on the piece, in relief, outside the code: a «Message us» or «Orders by WhatsApp» next to the square. That costs not one module and is what makes somebody bother to take their phone out.

Which piece for where it is going

On a counter or a table: a 70 mm desk stand. The customer has it a hand's width away, it stands on its own and takes no room.

In the window, to be read from the street: a wall plate of 120 mm or more. Here distance is in charge: a code reads comfortably at about ten times its width, so a metre and a half wants 150 mm. If it goes on the inside of the glass, make sure the sun is not on it at the brightest hour, because the reflection hides it.

To hand out: a 40 mm keychain. Careful here: it is the smallest piece, so it is where the pre-written message does most damage. On a keychain, the number only.

To give in person: a 3D printed business card. It is the most demanding piece of all, because the size is set by a pocket and the number with its country code already eats part of the link.

The exact dimensions of each piece are in the keychain guide and the desk stand guide.

What this code does not do

Worth knowing so you do not promise too much:

• It is not the WhatsApp Web code. That is the one scanned from the app to sign in, it changes every few seconds and there is no sense at all in printing it.
• It does not add the contact to the address book. It opens a chat; if the customer wants to save you, they do it themselves.
• It does not work if the number has no WhatsApp. It sounds obvious, but it happens with landlines: if your business has a landline and a mobile, the one in the code has to be the one with the account.
• If you change number, the piece stops working. So if you are going to print many, it is worth pointing the code at a redirect of your own rather than straight at wa.me: the day you change number, you change the destination and the pieces keep working. It is explained in the link guide.