Glossary Term
What Is QR Code Error Correction?
QR error correction adds recovery data so a symbol may remain readable when some modules are dirty or damaged.
QR Code error correction adds recovery codewords to the original data. When part of the symbol is dirty or damaged, a scanner can try to reconstruct the missing information. QR Code uses Reed–Solomon error correction and offers four levels: L, M, Q, and H.
Comparing the Levels
| Level | Approximate codeword recovery | Consideration |
|---|---|---|
| L | about 7% | More room for data |
| M | about 15% | A common choice for normal conditions |
| Q | about 25% | Greater resistance to damage |
| H | about 30% | Highest recovery, denser pattern |
These percentages are not permission to cover arbitrary parts of a QR Code. Success still depends on the location of damage, data volume, print size, contrast, quiet zone, camera, and surface condition. A higher level adds modules, making the code denser or requiring a larger print size.
Choosing a Level
Select a level that matches the environment. Clean digital or printed materials often do not need the highest setting. Packaging, dusty environments, or designs with a logo may need more tolerance, but a logo must still avoid the position patterns in three corners. Always test the final design on several devices.
When creating a QR Code for an s.id link, prioritize readability over decoration. Keep a high-resolution source and avoid compression that blurs individual modules.