How a Wi-Fi QR code works
A Wi-Fi code is just text in a standard shape that phone cameras understand. It looks like WIFI:T:WPA;S:HomeNet;P:mypassword;; where T is the security type, S is the network name and P is the password. When someone scans it, their phone offers to join that network. No app is needed on current iPhone and Android devices.
Because the password is inside the code, anyone who scans it can join. Treat a printed Wi-Fi code like you would the password written on a card.
On iPhone, point the camera at the code and tap the banner that appears. On most Android phones the camera or the Google Lens button does the same, and some models also have a scan option inside the Wi-Fi settings. After joining, the phone remembers the network like any other.
Choosing the right security type
Most routers made in the last decade use WPA2 or WPA3, and for both you choose WPA here. WEP is an outdated scheme that you should only select if your device still uses it, and you should consider replacing it. Choose none only for an open network that has no password.
Check your router label or its admin page if you are unsure. A wrong security type is the number one reason a scan opens the prompt but then fails to connect.
If a guest says the code scanned but the phone shows a wrong password message, retype the password into this tool slowly. Lowercase L and capital I look alike on many screens, as do zero and the letter O.
Special characters and hidden networks
Characters such as semicolons, colons, commas and backslashes have a meaning inside the code format. The tool escapes them for you so that a tricky password still works. Type the name and password exactly, including capital letters, because they are case sensitive.
If your network name is hidden, tick the hidden option. Otherwise, phones may not find it when they try to join. Hidden networks are not much of a security feature, and they can make connecting slower, so most home users leave this off.
Where to put the code
Printed on a card by the front door, inside a holiday rental's welcome folder, or on a cafe table, a Wi-Fi code saves a lot of typing. Use dark ink on white paper, keep the quiet zone around it, and raise error correction to Q for cards that will be handled often.
If you change your password, the old code stops working, and you need to make and print a new one. Guests who already joined are not affected until their device reconnects. For a guest network, consider a separate password you can change without touching your own devices.