Data Redundancy

Data redundancy adds recovery data so originals can be restored from partial loss. QR code error correction uses Reed-Solomon redundancy: Level L ~7%, M ~15%, Q ~25%, H ~30% redundant data.

Trade-off: more redundancy increases damage resistance but requires larger QR code versions for the same data. Design QR codes with center logos treat covered modules as "damaged" - Level H's 30% redundancy theoretically allows 30% logo coverage, though 20% is recommended in practice.