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Why a QR code still scans with a logo slapped on it
💡 A QR code's built-in Reed–Solomon redundancy lets a scanner rebuild the data even when up to ~30% of the code is damaged or covered — which is how a logo can sit in the middle.
The black-and-white squares aren't a random bitmap — they're a carefully layered data structure. QR codes ("Quick Response") were invented in 1994 by Masahiro Hara at Denso Wave, a Toyota-group supplier, to track car parts faster than the barcodes then in use. A 1D barcode holds ~20 characters; a QR code can pack thousands because it stores data in two dimensions.
The three big nested squares in the corners are finder patterns. A scanner locates them first to work out the code's position, rotation, and scale — which is why you can scan it sideways or at an angle and it still works.
The real trick is Reed–Solomon error correction — the same math that protected data on CDs. Extra redundant bytes are woven throughout the code, so a scanner can rebuild the original data even if part is dirty, torn, or covered. QR codes offer four levels, from L (~7%) up to H (~30%) of the code recoverable. That's exactly why brands can drop a logo in the middle: at a high correction level, the damaged region is simply reconstructed from the redundancy spread across the rest.