How QR code error correction works
Ever noticed a QR code still scans with a logo in the middle or a scratch across it? That's error correction — built-in redundancy that lets a scanner rebuild missing data.
The four levels
- Level L (Low) — recovers about 7% of the code.
- Level M (Medium) — about 15%.
- Level Q (Quartile) — about 25%.
- Level H (High) — about 30%.
The trade-off
Higher error correction survives more damage but adds more modules, making the code denser for the same amount of data. For clean digital use, a lower level keeps the code simple; for printed codes that may get scuffed — or codes with a logo overlaid — a higher level is safer.
FAQ
- How much of a QR code can be damaged and still work?
- Up to roughly 30% if it was generated at the highest error-correction level (H). At lower levels the tolerance is smaller. Either way, a clean, undamaged code always scans most reliably.
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