QR code error correction levels

Level	Recovery	Use case
L (Low)	~7% damage	Clean environments; maximum data density
M (Medium)	~15% damage	General use (default)
Q (Quartile)	~25% damage	Industrial, some logo overlay
H (High)	~30% damage	Heavy logo overlay; outdoor/industrial

Data capacity

A QR code's data capacity depends on content type, error correction level, and version (1–40). Version 40-L can store up to 7,089 numeric characters or 4,296 alphanumeric. URLs are typically 30–200 characters - Version 2–6 is sufficient for most links.

Logo overlay guide

Adding a logo to a QR code requires careful attention to maintain scannability:

Use error correction level H (30%) — the logo covers part of the code, and H-level recovery ensures the data remains readable.
Keep the logo to ≤20–25% of the total QR code area. Larger logos break too many modules.
Center the logo precisely — offset placement can interfere with the finder patterns in the corners.
Always test the final image on multiple devices (iOS Camera, Android Camera, a dedicated scanner app) before printing or publishing.

Color contrast requirements

QR codes require sufficient contrast between the dark modules (foreground) and light background. A minimum contrast ratio of 4:1 is recommended. Inverted codes (light on dark) work but some older scanners and ambient-light environments struggle with them. Avoid dark-on-dark, low-saturation color combinations, or gradients that reduce local contrast in the scanning area.

Print size minimums

A QR code should be at least 2 × 2 cm (0.8 × 0.8 inches) to scan reliably at arm’s length (≈30 cm). For scanning at greater distances (wall posters, billboard, storefront), scale proportionally: double the scan distance requires roughly double the code size. Always include a quiet zone (white margin) of at least 4 modules on all sides.