Why Damaged QR Codes Can Still Work
A QR code can lose part of its pattern and remain readable because redundancy is built into the data.
A QR code looks fragile. Yet cover part of it, scratch the label, or print it imperfectly and a phone may still read it.
The short answer
QR codes can contain error-correction data. The code stores extra mathematical information that can help reconstruct a limited amount of missing or corrupted data.
What the scanner is doing
The finder patterns help the scanner determine orientation and geometry. Once the grid is understood, the encoded data and its error-correction information can be interpreted together.
The exact tolerance depends on the error-correction level chosen when the QR code was generated.
Why it matters
The same idea appears across digital systems: reliable information often requires storing more than the bare minimum.
Data becomes more reliable when the system is designed to expect errors.
Sources
Replace this sample section with the authoritative sources used for the final Wondecode article.