How to make an SMS QR code

The SMSTO: format

An SMS code holds one short line of text:

SMSTO:+12025550147:JOIN

That is SMSTO:, the phone number, a colon, then the message. The message runs to the end of the code, so it can contain colons of its own. The iPhone Camera and Android scanners built on ZXing, the open-source barcode library behind many of them, read this form and open a new message with the number and the text filled in.

Nothing is sent by scanning. The person sees the message, can change it, and decides whether to press send. That matters for consent, and it means an SMS code can’t text anyone on its own.

You may also meet sms: links, the form web pages use for “text us” buttons. Phones have disagreed about how a message is written into those, which is one reason QR generators write SMSTO:.

Write the number in full international format, with a plus sign and the country code. It then works from any phone, including a visitor’s phone on a different network or a SIM from elsewhere. Spaces and brackets are for people; the code needs only the digits and the plus.

Pre-filled text and its length

A single text message holds 160 characters from the standard SMS character set (GSM-7: plain letters, digits and common punctuation). If any character falls outside it, such as an emoji, a curly apostrophe or many accented letters, the whole message switches to a wider encoding and the limit drops to 70. Longer messages are split into parts of 153 or 67 characters, joined again on the receiving phone, and each part can count as a message on the sender’s bill.

So keep the pre-filled text short, and type a straight apostrophe (') rather than a curly one (’) if your keyboard offers the choice. Two patterns work:

• A keyword: JOIN, MENU, VOTE A. Your SMS service recognises it and replies automatically. The code saves people from mistyping it.
• A starter line they finish themselves: “Hi, I'd like a call back about a quote. My name is ”. They add their name and press send, and you know what the text is about.

The message also makes the code denser. Unlike a web link, SMS text goes into the code as typed, without percent-encoding, so it grows slowly:

Where SMS codes work well

• Opt-ins and keyword entries. “Text JOIN for weekly offers”, a competition entry, a vote at an event. The code fills in both the number and the keyword, which is where people make mistakes.
• A quiet “text us” line. Many people would rather text than phone: a tradesperson’s van, a salon’s appointment card, a support line on a product. A starter line gets you a useful first message.
• Places with poor data. A text needs only a basic mobile signal, not mobile data, so an SMS code works in a rural car park or a basement where a web link would hang.
• People without smartphone apps you rely on. Every mobile phone can text; not every customer uses WhatsApp. If most of yours do, a WhatsApp code opens a chat instead.

Phone and carrier differences

• Scanner apps vary. The camera on recent iPhones and Android phones opens the message; a few scanner apps show the text and need another tap, or only display it.
• Dual-SIM phones may ask which line to send from.
• Tablets and Wi‑Fi-only devices can’t send ordinary texts at all.
• Short codes, the four- to six-digit numbers that text services use, usually work only on networks in the country they belong to. A visitor roaming on a foreign network may not be able to text one, so give a full number as well if visitors matter.
• Cost. The sender pays their usual rate for each message part, often covered by their plan. Premium-rate numbers cost more, and the rules in most places require the price to be clear on the sign; check them before using one.
• Your end. The number has to accept texts. Mobiles and SMS service numbers do; many landlines don’t unless the provider has switched it on. Text it yourself before printing.

Consent and opt-out wording for marketing texts

When the texts you send back are marketing, the rules in most places are strict. In general you need the person’s clear consent, you must say who you are, and every message must give a free, easy way to stop. Requirements differ between countries and change, so check the rules for where you and your customers are, and your SMS provider’s terms, which often add their own. This is a guide, not legal advice.

Next to the code, say plainly:

• who is texting and what they will send: “Weekly offers from Corner Café”;
• how often: “about four texts a month”;
• that the sender’s usual message rates apply;
• how to stop: “Reply STOP at any time”, and where to get help;
• where your privacy notice is, as a short web address.

For example:

Join our text club: weekly offers from Corner Café, about four texts a month. Scan to text JOIN to +1 202 555 0147. Your usual message rates apply. Reply STOP at any time to unsubscribe. Privacy: cornercafe.com/privacy

Honour STOP at once, keep a record of who opted in and when (SMS services do this for you), and don’t add someone to a marketing list just because they texted you a question.

Print it and test it

SMS codes are small, so size them for the distance: about a tenth of it, so 3 cm on a card read from 30 cm and 10 cm on a poster read from a metre. Then test:

1. Scan the printed proof with an iPhone and an Android phone. Each should open a new message to your number with the text in place.
2. Send it. Check it arrives, and that any automatic reply comes back with your name and the STOP wording.
3. Reply STOP from the test phone and check it works.
4. If visitors matter, try a phone on a different network.

Make it in QR Island

In the studio, choose SMS, type the number (spaces, brackets and dashes are fine: the studio keeps only the digits and the plus sign) and an optional message. Pick a world, such as English Cottage, and press Get QR code for the flat code to print, with PNG and SVG downloads and the free print sheet. Free codes are made in your browser, the number is never sent to our server, and the code never expires. The island sign pack (+US$4.99, added to an Island pack) has a “Scan me” template whose headline and subline you write yourself, with room for the opt-in wording.