A spot covers part of a QR code, and yet the reader still finds its content. The program does not necessarily guess the missing squares from their appearance. The symbol contains additional information to correct certain errors. Its robustness also comes from information added before printing.
Denso Wave describes the use of a Reed-Solomon code and four levels of correction. Increasing this protection requires more space for the same useful information. The choice depends in particular on the medium of use: a label exposed to soiling imposes other compromises than a code presented under specific conditions.
The advertised percentages are code words, eight-bit data units, and not a warranty on any portion of the hidden surface. Deterioration can exceed reconstruction capabilities. Redundancy thus makes it possible to find a message despite certain losses, within the limits provided by its encoding.
What we know
The rates are for code words, not on any erasable surface.
To go to the source
References consulted on September 21, 2026. Linked pages may be in another language.
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