What a phone does when it scans a Wi-Fi code
A Wi-Fi code is a line of text in a format phones know, such as WIFI:T:WPA;S:Guest Wi-Fi;P:welcome2026;;. It lists the security type (T), the network name (S) and the password (P). A phone that understands it offers to join the network.
- iPhone: the Camera app recognises the code and shows a prompt to join the network. This has worked since iOS 11.
- Android: recent versions can read the code from the camera, Google Lens or a quick settings scanner and offer to connect. Older versions need a scanner app. The wording and buttons differ between makes and versions.
- Laptops and other devices: most do not read Wi-Fi codes, so they still need the password typed in. If guests bring laptops, put the password in words next to the code.
Phones ask before they join, so scanning the code does not connect a phone by itself.
The password is in the code, in plain text
A Wi-Fi code does not protect the password. Guests who scan it never have to see the password, but the code holds it all the same, and any scanner app can show it to anyone who can see or photograph the code. That includes people who are not guests.
- Use your router's guest network for a code that is on display. It keeps visitors away from your own computers, printers and files, and you can change its password without touching your own devices.
- Place the code where only guests can reach it. A code in a front window can be photographed from the street.
- Change the password if the code has gone further than you meant. The old code stops working at once, and you make a new one.
- Never put the password of your main network on a poster. Pick a long random one for the guest network, for example from the password generator.
Choosing the security type
- WPA / WPA2 / WPA3: the right choice for nearly every home and business router. The code stores the type as WPA, and phones join WPA2 and WPA3 personal networks with it. If your router allows only WPA3, test the code with the phones your guests use, because older devices may not support WPA3.
- WEP: an old type that is easy to break. Choose it only if a very old router forces it. Many current phones warn about WEP or will not join it.
- No password: for an open network. The code then holds only the name. Anyone nearby can join an open network, and what is sent over it without encryption can be seen by others nearby.
- Hidden network: a hidden network does not announce its name, so the phone has to be told to look for it. Hiding a network adds very little security, and some phones connect to a hidden network more slowly.
Getting the details exactly right
A code with a wrong capital letter still scans, but the phone then fails to connect. Copy the name and the password from the router or from a phone that already connects, character for character.
The characters \, ;, ,, : and " have a special meaning inside a Wi-Fi code, so the tool puts a backslash in front of them. Phones that follow the format read them back correctly. If a guest cannot connect and your password uses one of these symbols, try the code on that guest's phone, or choose a password without them.
A network name with accents or another script is stored as UTF-8. The 32 byte limit counts bytes, not letters, so a name in accented or Chinese, Japanese or Korean characters runs out sooner than an English one.
Codes for Wi-Fi are small. At medium error correction a network like Guest Wi-Fi with a short password is 29 by 29 squares, so even a code printed 3 cm wide has squares of about 0.8 mm, which is easy to scan. See the QR code generator page for colours, error correction and print size.