A Wi-Fi QR plate: let the guest connect without typing anything

By Tiehl Roberto Matías · 7 min read · Updated 27 October 2026

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A Wi-Fi QR code does not carry a link: it carries an instruction with the network name and the password, which the phone understands and applies on its own. Done right, the guest points the camera and is in. Done wrong, it fails every time on the same character.

What is inside a Wi-Fi QR

It is not a web address. It is a string in a format of its own that Android and iOS have recognised for years:

WIFI:T:WPA;S:NetworkName;P:thepassword;;

Each letter has its job:

Field	What it is	Values
T	Security type	WPA, WEP or nopass
S	Network name (SSID)	Exactly as it is, capitals included
P	Password	Omitted if the network is open

The two semicolons at the end are not spare: they close the last field and close the string. Without them, some readers do not interpret it.

The characters that break the code

This is the cause of 90 % of Wi-Fi QR codes that do not work. Because the format uses the semicolon and the colon to separate fields, if your password contains either of them it has to be escaped with a backslash. Five characters are affected:

Character	Written as
semicolon ;	\;
colon :	\:
comma ,	\,
double quote "	\"
backslash \	\\

A password like Guest:House;2026 has to travel inside the code as Guest\:House\;2026. Put in as it stands, the reader thinks the password field ended at the colon and hands the phone a truncated key.

Which phones support it

• iPhone: since iOS 11, with the ordinary camera. A notice appears at the top, you tap it and you are connected.
• Android: since Android 10 with the camera. On earlier versions you need Google Lens or the system code reader.
• Computers: no. A laptop cannot scan its own screen, so it is worth having the password written on the plate in readable text as well.

Size of the plate

A Wi-Fi plate gets scanned from close up, half a metre at most, so it does not need to be large. What it does need is for the code not to run short of modules, and here the string is longer than it looks: network name, password and the format's own labels add up fast.

Network + password	Total characters	Version (level M)	Minimum side of the code
Short (network 8, key 8)	34	3 — 29 × 29	29.6 mm
Medium (network 15, key 12)	45	4 — 33 × 33	32.8 mm
Long (network 20, key 20)	58	4 — 33 × 33	32.8 mm
Very long (network 24, key 24)	66	5 — 37 × 37	36.0 mm

In practice a plate 90 to 120 mm tall leaves plenty of room for the code, a title and the password in text, with the modules very comfortable.

The two screw holes

If the plate is going to be screwed up, the holes go outside the code's quiet zone, at the top and bottom ends or in the four corners. A 4 mm diameter for a 3 mm screw, and at least 4 mm of material between the hole and the edge.

If you would rather stick it, double-sided foam tape works well on tiles and on painted walls, and comes off without taking the paint. Leave the back face flat, with no infill showing.

Where to hang it

If you want it poster-sized, for the lobby of a larger property, look first at the oversized codes guide: hanging it higher nearly always beats making it bigger.

There are two separate questions: where to put it and what to fix it with. The second has more to it than it looks, because the hole in the plate falls inside the area the code needs plain, and that is in the guide to hanging the plate.

For the location, it seems like the least of it and it decides whether the thing gets used:

• At eye level, not at socket level. Scanning while crouching is awkward.
• Near the entrance or the table, which is where the guest takes their phone out on arrival.
• Not opposite a window. Backlight is the camera's worst enemy. On a side wall it scans far better.
• Not under a direct spotlight, especially if the filament has any shine.

And make it a flat wall. Sticking it to the fridge, a jar or the router itself looks convenient, but a curved surface distorts the grid and has a measurable limit: the code cannot exceed half the diameter of whatever holds it, as the curved surfaces guide explains.

Before printing the final one

A Wi-Fi QR has a trap the others do not: you cannot test it while already connected to that network. The phone scans, sees it is already on it, and does nothing, so it looks as if the code has failed when in fact it is fine.

To test it properly: forget the network in the phone's settings, or turn Wi-Fi off and on again, and then scan. Better still, test it with somebody else's phone that has never connected.

A note on security

The password travels inside the code in plain text: anybody who photographs the plate has it. For the guest Wi-Fi of a holiday flat or a bar that is exactly what you want. For your main home network, it is not.

The sensible thing is to set up a guest network on the router — nearly all of them have one — and put only that on the plate. The guest gets internet and does not get access to the printer, the network drive or the cameras.