Quick answer
QR codes use Reed–Solomon error correction to recover data when some modules cannot be read. The four levels—L, M, Q, and H—add progressively more recovery data. Higher correction improves tolerance to damage but also produces a denser or larger symbol for the same payload.
How to do it
- Use a normal level for clean digital or printed codes without a logo.
- Use higher correction when adding a small center logo or expecting limited wear.
- Never rely on correction to compensate for poor contrast or covered finder patterns.
Approximate recovery capacity
The commonly cited recovery figures are about 7% for L, 15% for M, 25% for Q, and 30% for H. These are useful guidelines, not guarantees that any matching area can be removed. Damage location matters, and the finder, timing, or format regions remain essential.
Why higher is not always better
More correction bytes leave less room for content at a given version. The generator may increase the grid size, which makes each module smaller when printed at a fixed width. For a clean short URL, a moderate level can scan more easily than an unnecessarily dense H-level symbol.
Common mistakes to avoid
- Covering 30% of a code because level H is selected.
- Ignoring how density changes the physical module size.
- Using correction as a substitute for testing.
Try the related tool
Use QRFoundry directly in your browser. Tool inputs and uploaded files are processed on your device.
Open QR Code Generator