QR Code Error Correction Levels Explained
Every QR code has a built-in error correction level — a setting that determines how much of the code can be damaged, smudged, or covered before it stops scanning. Most QR generators hide this setting. PV QR Codes lets you control it, and choosing the right level can dramatically improve scan reliability.
The four levels
- L (Low): up to 7% of the code can be damaged
- M (Medium): up to 15% of the code can be damaged
- Q (Quartile): up to 25% of the code can be damaged
- H (High): up to 30% of the code can be damaged
The tradeoff: error correction vs. code density
Higher error correction means more redundant data is encoded, which means more black squares in the code, which means the code becomes visually denser. A code at level H has roughly twice as many modules as the same code at level L.
Denser codes are harder to scan from a distance because each module is smaller. So the choice isn't "more error correction is always better" — it's a balance between damage tolerance and scan distance.
When to use each level
- L — clean digital displays only (screens, well-printed paper). Rarely the right choice for print.
- M — standard for most printed materials in clean environments (menus, brochures, business cards).
- Q — when adding a logo overlay or printing on materials that may get smudged (signs, packaging).
- H — outdoor signage, vehicle wraps, packaging, anything with a logo embedded in the center.
Why logos require Q or H
When you place a logo in the center of a QR code, you're physically covering part of the data. With L-level correction, even a small logo can break the code. With H-level correction, you can cover up to 30% of the code and still have it scan reliably.
PV QR Codes automatically bumps the error correction level to Q or H whenever you add a logo, so you don't have to think about it.
Always test after generating
Regardless of the level you choose, test the final code on at least two phones before printing. The error correction level controls the theoretical maximum, but real-world reliability depends on print quality, contrast, lighting, and scanner software.