What Is a QR Code?
A QR (Quick Response) code is a two-dimensional matrix barcode invented by Denso Wave in 1994. Unlike traditional barcodes that store data in one dimension, QR codes store data both horizontally and vertically, allowing them to hold significantly more information in a compact square shape. They can encode up to 3,000 bytes of binary data or 7,089 numeric characters. QR codes are used globally for payments, product tracking, advertising, and contactless information sharing.
Error Correction Levels Explained
QR codes use Reed-Solomon error correction to remain readable even when parts of the code are damaged, dirty, or obscured. There are four levels: L (Low, recovers 7% of data), M (Medium, 15%), Q (Quartile, 25%), and H (High, 30%). Higher correction levels add redundancy, which increases the physical size of the QR code for the same data payload. Use level H when embedding a logo in the center of a QR code or when the code will be printed on surfaces subject to wear.
Best Practices for Printing and Displaying QR Codes
Always test a printed QR code before mass production. Ensure a minimum quiet zone (white border) of four module widths around the code so scanners can locate the finder patterns. Maintain a contrast ratio of at least 4:1 between the foreground and background colors. For outdoor use, laminate printed codes to protect them from moisture and UV damage. Minimum recommended print size is 2 cm × 2 cm for standard viewing distances; increase size proportionally for codes placed more than 1 metre away from the user.
