URI

A URI (Uniform Resource Identifier) uniquely identifies internet resources or abstract concepts. URLs (locators) and URNs (names) are both URI subtypes. https://example.com/page is both a URL and a URI.

Most QR code data uses URI format. Web links (https://...), email (mailto:...), phone calls (tel:...), Wi-Fi (WIFI:...), TOTP authentication (otpauth://...), and maps (geo:...) all use URI schemes that determine post-scan device behavior.

URI design matters in QR code generation. Phone numbers need international format for global compatibility. vCard data requires proper percent-encoding for non-ASCII characters.

GS1 Digital Link expresses product identification numbers (GTINs) as URIs (https://id.gs1.org/01/...), transforming numeric product codes into scannable web links. URIs are the common language structuring QR code contents and instructing devices on appropriate actions.