What does a Wi-Fi QR code actually contain? One short line of text. For a network called Guest WiFi with the password pass;word, it is:
WIFI:T:WPA;S:Guest WiFi;P:pass\;word;;Phone cameras recognize this format and offer to join the network. The code above decodes back to exactly that line, backslash included, and you can see your own version under “Text inside the code” below the preview.
What do T, S and P stand for?
T is the security type: WPA when you pick WPA/WPA2/WPA3, WEP, or nopass for None. S is the network name (SSID) and P the password. The phone reads them in that order and fills in what a guest would otherwise type by hand.
My password has a semicolon or quotes. Will it break?
No. Five characters have a job in this format: the backslash, semicolon, comma, colon and double quote. The generator puts a backslash in front of each one, as in pass\;word above, and the phone removes it again when it reads the code. Everything else goes in exactly as typed, which also means a stray space at the end of the network name or password stays in. Copy both from the router’s settings page or its sticker rather than from memory.
What about a hidden network?
Tick “Hidden network”. The code then ends with H:true, which tells the phone to look for the network even though it does not announce its name. The name has to match to the letter, since the phone cannot pick it from a list.
Where should the code go?
Near where people ask for the password: by the front door, on a café table, in the welcome folder of a holiday rental, at a meeting room entrance. A separate guest network is worth setting up for any of these. Visitors then never share a network with your own computers and printers, and changing the guest password later only means reprinting one card. Before you laminate anything, print a proof and scan it with two different phones.