QR (Quick Response) codes are two-dimensional barcodes that can store various types of information including text, URLs, contact information, WiFi credentials, and more. They were invented in 1994 by Denso Wave for tracking automotive parts but have since become widely used for marketing, payments, and information sharing.
Error correction levels determine how much of the QR code can be damaged while still remaining readable. Low (7%) is suitable for clean environments, Medium (15%) is the standard level, Quartile (25%) is good for industrial use, and High (30%) is best for environments where the code might get damaged or dirty.
QR codes can store up to 4,296 alphanumeric characters or 7,089 numeric characters. They're widely supported by smartphone cameras and dedicated QR code readers. Common uses include website links, contact cards (vCard), WiFi network sharing, payment information, and product tracking.