How does a QR code work technically?

The Structure

• Position detection pattern – the three large squares in the corners. A reader detects position and rotation based on these.
• Alignment pattern – smaller squares that compensate for distortions, such as on a curved bottle.
• Data area – where the actual characters are located.
• Error correction – additional information used to reconstruct damaged areas.

The Four Error Correction Levels

A logo can be placed in the center because error correction compensates for the obscured area. However, this is only possible up to the limit of the selected level – using a large logo at level L may produce a code that sometimes works and sometimes doesn't.

Why short addresses are better

The more characters stored, the finer the pattern becomes. A fine pattern requires more printing space and is harder to read. This is where dynamic QR codes have a technical advantage: they contain only a short redirection address, regardless of how long the actual target is.

Standard

QR codes are standardized in ISO/IEC 18004. They are freely usable without license – the inventor Denso Wave has waived its patent rights.