DPI

DPI (Dots Per Inch) measures resolution by counting dots placed within one inch (2.54 cm). Higher DPI means denser dots and finer images. Office printers output 300-600 DPI; commercial printing exceeds 1200 DPI.

For QR code printing, DPI directly determines scan reliability. Each module (black or white square) must be printed large enough for cameras to identify accurately. Insufficient DPI causes module boundaries to blur and adjacent modules to merge, triggering scan errors.

The practical guideline is minimum 300 DPI for QR code printing. Business cards and flyers read at close range work well at 300 DPI. Posters and signs read from distance compensate by increasing QR code physical size. The key metric is dots per module - at least 3x3 dots per module ensures stable scanning across most readers.

When generating raster QR codes (PNG, JPEG), output DPI settings matter. A 72 DPI screen-resolution image printed directly produces blurry modules. Always export at 300+ DPI for print, or use vector formats (SVG, PDF) to eliminate DPI constraints entirely.