Wi-Fi QR code generator

What this tool does

It writes the name of the network, the kind of security and the password in the format that phones understand as a Wi-Fi login. Many phone cameras recognise such a code and offer to join the network. On a phone that does not, a scanner app that supports Wi-Fi codes does the same.

The password is used by your browser to draw the code and for nothing else. It is not sent to this site.

How to use it

1. Enter the network name exactly as your router shows it. Capital letters and spaces count.
2. Choose the security: “WPA or WPA2” for a network with an ordinary password, “WEP” only for an old router that still uses it, “None” for a network without a password.
3. Enter the password. Tick “Show password” to check what you typed.
4. Tick “Hidden network” only if the network does not appear in the list of networks on a phone.
5. Create the code and join the network with your own phone as a test before you print the code.
6. Under “Print a sign or cards”, choose a sign, a folding table card or eight small cards, decide whether the network name and the password are printed as text, and press “Print”.

How the code is made

The content of the code is one line of text that starts with WIFI: and lists the fields T for the security, S for the network name, P for the password and, for a hidden network, H. Every field ends with a semicolon and the line ends with a second semicolon.

A backslash, a semicolon, a comma, a colon or a double quote inside the name or the password would be mistaken for a part of the format. The tool puts a backslash in front of each of them, which tells the phone to take the character literally.

The tool checks what can be checked: a network name is at most 32 bytes long, and a WPA or WPA2 password has 8 to 63 characters or is a key of exactly 64 hexadecimal digits. It cannot check whether the password is the right one.

Worked example

A café has the network Cafe Guest with the password latte;2026. The content of the code is:

WIFI:T:WPA;S:Cafe Guest;P:latte\;2026;;

The semicolon in the password got a backslash. The line is 39 bytes long, so at level M the code is version 3 with 29 by 29 modules.

Printing a sign

The print layouts use the print dialog of your browser, where you can also save a PDF instead of printing. They fit both A4 and US Letter paper with margins of 10 mm, and the page is printed white with the code in its own colours, also when your screen is in dark mode.

The page also tells you how wide one module will be on paper. For the café example (version 3, 37 modules including the margin) that is about 3.2 mm on the sign and 1.0 mm on a card. Print at 100% scale; “fit to page” changes the sizes.

Printing the network name and the password as text helps guests whose phone does not scan Wi-Fi codes. Leave the password off a sign that strangers can see, for example in a shop window. The code itself still contains the password.

Security notes

• The password is stored in the code as readable text. Everybody who can photograph the code can read the password, also later and from a picture.
• Show the code where your guests are, not where it can be seen through a window or in photos that you publish.
• Use the guest network of your router for the code if it has one, so that guests do not reach your own devices.
• When you change the password, the old code stops working. Create and print a new one.
• WEP is an old kind of security with known weaknesses. If your router still uses it, switching the router to WPA2 or WPA3 protects you better than any code.

Colours, logo and the automatic check

Under “Colours and logo (optional)” you can choose the colour of the code and of the background, and put a logo from your device in the middle. The logo is opened by your browser and is not uploaded. The SVG file contains it as an embedded image, and the modules stay vector shapes.

A code needs contrast. The tool compares the luminance of the two colours: 0% for two equal colours, 100% for black on white. Below 40% it does not create the code, and below 70% it warns. These limits are our convention, borrowed from the grades of symbol contrast in ISO/IEC 15415, the print-quality standard for two-dimensional codes; colours on a screen only approximate printed ink. A code that is lighter than its background is read by some scanners and not by others, so the tool warns about that as well.

With a logo the tool always uses error correction H and leaves a square in the middle free of modules, about 22% of the width of the code, which is 3% to 6% of its area. Level H can restore about 30% of the codewords.

Before the download buttons work, the tool reads the finished PNG image back with a separate decoder (jsQR) and compares the text with what you entered. A coloured code or a code with a logo that does not read back is not offered for download. For a plain black-and-white code a failed check is only reported, because the encoder itself is tested with two decoders. The check shows that this decoder reads the image in your browser; it does not replace a test with real phones.

Common mistakes

• A different spelling of the network name, for example cafe guest instead of Cafe Guest. The phone then searches for a network that does not exist.
• A space at the end of the name or the password, often caused by copy and paste. The tool warns about it.
• The wrong kind of security. A code that says “None” cannot join a protected network.
• Ticking “Hidden network” for a visible network. Leave it off unless you know that the name is not broadcast.

Sources

• Cognex: ISO/IEC 15415 grading, symbol contrast
• ZXing project: format of Wi-Fi codes
• Wikipedia: Wi-Fi Protected Access
• Wikipedia: Service set (network names)