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Rounded and Circular Module Styles

Standard QR code modules are square, but rounded, circular, and other stylised shapes are increasingly popular for design purposes. Understanding scanner compatibility ensures these artistic choices do not sacrifice functionality.

Common Module Styles

Dot style: Each module is a circle instead of a square. Gaps between modules create an open, modern appearance.

Rounded square: Corners of each module are radiused. Subtle rounding maintains readability while softening the appearance.

Organic shapes: Irregular module shapes that give the QR code an artistic, hand-drawn feel.

Mixed styles: Different shapes for data modules vs structural elements (finder patterns, alignment patterns).

Scanner Compatibility

Scanners detect modules by sampling the centre of each grid position. Module shape matters less than:

1. Centre accuracy: The centre of each module must correctly represent the bit value (dark or light)
2. Coverage: Each module must fill enough of its grid cell to be unambiguous
3. Contrast: Dark modules must be clearly darker than light modules

Dot style can reduce module coverage below 50% of the grid cell, potentially causing scan failures — especially at smaller print sizes or greater distances.

Safe Module Sizes

For reliable scanning with non-square modules:

• Module fill should cover at least 60% of the grid cell area
• Dot diameter should be at least 70% of the module width
• Rounded corner radius should not exceed 30% of the module width

Finder Pattern Treatment

The three finder patterns are detected by their 1:1:3:1:1 ratio. Rounding finder pattern modules is generally safe (the ratio is maintained), but excessive modification can reduce detection reliability.

Best practice: Keep finder patterns as standard squares and apply styling only to data modules.

Testing Rounded Designs

Rounded and styled QR codes require more rigorous testing than standard codes:

• Test at the minimum expected print size
• Test at maximum expected scan distance
• Use EC Level M or higher to compensate for reduced module fill
• Test with at least 5 different scanner apps

Key Takeaways

• Module centre accuracy matters more than module shape
• Dot-style modules should fill at least 60% of the grid cell
• Keep finder patterns in standard square format for reliable detection
• Higher EC levels compensate for reduced coverage from stylised modules
• Test more rigorously than with standard square modules