Common QR Code Error Correction Levels Explained: When to Use Which
Discover the mathematical principles of Reed-Solomon error correction in ISO/IEC 18004 symbols. Learn how Levels L, M, Q, and H recover torn, stained, or logo-covered data.
1. The Four Error Correction Levels
- Level L (Low): ~7% codeword recovery. Maximum data capacity; ideal for dense payloads and screen displays.
- Level M (Medium): ~15% codeword recovery. The standard default for retail packaging and marketing.
- Level Q (Quartile): ~25% codeword recovery. Built for industrial manufacturing and corrugated shipping cartons.
- Level H (High): ~30% codeword recovery. Mandatory for embedding custom logos or outdoor exposure.
2. Why Logos Require Level H
Placing an emblem in the center intentionally destroys data modules. The decoder treats the graphic as damaged codewords, utilizing the ~30% recovery margin to reconstruct the missing information.
3. The Density Trade-off
Higher error correction increases the matrix version. If physical print dimensions remain constant, individual modules become smaller and more difficult for budget cameras to resolve.