How do QR codes work?
A QR code is text written in black and white squares, with markers so the phone can find it and spare data so it still reads when damaged.
What exactly is a QR code?
It’s a two-dimensional barcode, invented in 1994 by the Japanese company Denso Wave to track car parts. “QR” stands for Quick Response.
Unlike a classic barcode read along one line, it’s read across and down, which lets it store far more characters in a small area.
What are the big squares in the corners for?
They’re position markers: the phone finds them first to know where the code is, which way it’s turned and whether it’s seen at an angle. That’s why you can scan a code upside down or slightly skewed.
The light margin around the code also helps separate it from its surroundings; don’t cover it. Recommended sizes are in the minimum QR code size.
Why does a QR code still scan when damaged?
Because it includes error correction: part of the squares is redundant and lets the reader rebuild what’s missing. The standard has four levels, from L (lowest) to H (highest, which tolerates roughly 30% damage).
That’s what makes a logo in the middle possible. Scanotte uses level Q by default and switches to H as soon as you add a logo; see the QR code with a logo.
What can a QR code contain?
Just text, which the phone interprets by its format: a web address, a vCard contact, Wi-Fi settings, an e-mail address. The phone recognises the format and offers the matching action.
A QR code holds no app and no file: a “QR code for a PDF” actually holds the link to a PDF online, as explained in the QR code for a PDF.
What’s the difference between static and dynamic codes?
A static code holds the final information; a dynamic code holds a short address that redirects to an editable destination. Technically both are ordinary QR codes: only the content differs.
The full comparison is in static vs dynamic.
Why do some QR codes look denser than others?
Because they hold more data, or use a higher error-correction level. A long web address or a full contact card needs more squares than a short link.
Denser codes need to be printed bigger to stay readable, which is one reason short, editable links are popular on small labels.
Frequently asked questions
Can a QR code contain a virus?
The code itself only holds text. The risk comes from the link it opens: check the address before opening.
Does a QR code need the internet?
Not to read it. To open the link inside, yes. Wi-Fi and vCard codes work offline.
Can two identical codes lead to different pages?
No, the same pattern holds the same data. But a dynamic code can redirect elsewhere if its owner changes the destination.
Are QR codes free to use?
Yes, Denso Wave doesn’t enforce its rights on the standard: anyone can create and read QR codes.