A guest Wi-Fi sign whose code actually scans
Type the guest network's name and password. The page checks them for the characters and lengths that stop a phone joining, draws the QR code, and prints a sign at the right size for where it hangs. The code is drawn on this page, so the password isn't sent anywhere.
WIFI:T:WPA;S:Corner Cafe Guest;P:espresso-at-noon;;
T: security, S: name, P: password; a backslash protects \ ; , : "The sign
51 characters make a 33 × 33 grid (version 4). Scanned from 50 cm, the code needs to be at least 8.2 cm (3.23 in) wide with its blank margin. The printed sign uses exactly that; bigger always scans.
Point your phone's camera at the code, then tap the banner to join.
Before you put it out, scan the printed sign with an iPhone and an Android phone that have never joined this network.
What happens when a guest scans it
The iPhone camera and Android's camera or Google Lens read the WIFI: text and offer to join the network; the guest taps once and is online, with nothing typed. The phone saves the network like any other, so if you change the password, the old sign stops working and the saved network on every guest's phone does too.
- Use the guest network, not your main one. A printed password is a public password, and a guest network keeps visitors away from your till, printer and cameras.
- Plan for the password change. When you change it, reprint the sign the same day. A password that has no
\ ; , : "in it scans with every app and is easy to type for the guest whose camera won't cooperate. - The password is in the code in plain text. Anyone who photographs the sign can read it. That's fine for a guest network, and one more reason not to print your main network's password.
The full guide, with what each character does to the code and how big to print it, is in A Wi-Fi QR code for guests. For any other code, the print size calculator works out the width from the scan distance, and the QR code generator makes codes for links, email and text.