What is a QR code?
https://example.com/menu WIFI:T:WPA;S:Office Wi-Fi;P:password123;; BEGIN:VCARD…
A grid of squares with built-in redundancy.
A QR code is a grid of small squares called modules. Three larger squares in the corners tell the scanner where the code is and how it is oriented. The data is spread through the rest of the grid, together with error correction, so a code can still be read when part of it is dirty, damaged or covered by a logo.
There are four error correction levels, L, M, Q and H, which can recover roughly 7, 15, 25 and 30 percent of the code. More correction makes the pattern denser. More data does as well, which is why short content makes for simpler, easier-to-scan codes.
More than web addresses.
Web addresses
The most common use: open a page.
Plain text
A message, a code or an instruction.
Wi-Fi
Network name, password and security type, so phones can join.
Contact cards
A vCard that saves a contact.
Phone, SMS and email
Start a call or a message with details filled in.
Locations and events
A map point or a calendar entry.
Decide before you print.
A static code holds its content directly and can never change. A dynamic code holds a short link, so its destination can be changed, and its scans counted, after printing.
Common questions
Do QR codes expire? +
A static code never expires, because it contains its content. A dynamic code works for as long as the link behind it is active.
Can a QR code be tracked? +
Only if it points at a trackable link. A static code just contains data, so there is nothing to count.
How big should a QR code be? +
As a rule of thumb, about one tenth of the scanning distance, and not smaller than around 2 × 2 cm. The QR code size calculator works it out.
Can I put a logo in the middle? +
Yes. Error correction lets a code survive a small logo in the centre. Test the printed result on a few phones.