Pixel

A pixel (picture element) is the smallest square dot that makes up a digital image. Every image on a screen is a grid of pixels, each carrying a single color value. For QR codes, the number of pixels used to render one module (the smallest black or white square) directly affects how reliably the code can be scanned.

When generating a QR code image, the pixel count per module is often called the "module size." If the module size is too small, smartphone cameras may fail to focus properly. A minimum of 4 pixels per module is generally recommended for reliable scanning. For print, the required pixel count depends on the printing resolution (dpi) - at 300 dpi, even a 0.5 mm module renders with sufficient clarity.

Raster formats like PNG and JPEG can produce jagged edges (aliasing) when scaled up. To avoid this, either generate the image at a sufficiently high resolution from the start, or use a vector format like SVG. SVG is ideal for web display, while high-resolution PNG works best for print.