QR Code Error Correction Explained: L, M, Q and H

By November 14, 2026

Have you noticed that QR codes with a logo in the middle still scan? That works because of error correction, a feature built into every QR code. It lets the scanner rebuild missing data.

How error correction works

QR codes use a method called Reed-Solomon error correction. When the code is made, extra data is added next to your information. If part of the code is dirty, scratched or covered, the scanner uses the extra data to recover what is missing.

The four levels

  • Low (L): can recover about 7% of the code.
  • Medium (M): about 15%. A good everyday choice.
  • Quartile (Q): about 25%.
  • High (H): about 30%. Best when adding a logo or printing in rough conditions.

The trade-off

Higher correction means more extra data, so the code becomes denser with smaller modules. A dense code needs more print size and a better camera to scan. That is why you should not always pick High.

Which level should you choose?

  • Short link on clean paper or a screen: Medium.
  • Printed on packaging or outdoors: Quartile or High.
  • Code with a center logo: High.
  • Lots of data in one code: Low or Medium, so it stays readable.

What QRIQO does for you

In the QRIQO generator you can pick the level yourself under Customize design. When you add a logo, the tool switches to High automatically.

Do not rely on it too much

Error correction is a safety net, not permission to cover half the code. Keep any logo small, protect the three corner squares and always test-scan your final design.

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