Aztec code

The bullseye in the middle

Where a QR code locates itself with three corner finder patterns, Aztec (ISO/IEC 24778) puts one concentric square bullseye dead centre and grows data outward in rings. Two consequences follow. First, no quiet zone is required (the only major 2D symbology where that is true), so the code can run right against borders, text and artwork on a cramped ticket layout. Second, the reader parameters live in a ring around the bullseye rather than in fixed corners, letting error correction be tuned in fine steps instead of QR's four levels.

Symbols range from 15 × 15 (compact) to 151 × 151 modules, holding up to 3,832 digits or 1,914 bytes.

Why your boarding pass is an Aztec

The IATA bar-coded boarding pass (BCBP) standard specifies Aztec (alongside QR and Data Matrix) for mobile passes, and airlines overwhelmingly render Aztec; most European rail operators (Deutsche Bahn, SNCF, Trenitalia among them) use it for e-tickets. It scans well from phone screens, which is the daily reality of ticketing.

For your own projects the calculus is the reverse of the operators': dedicated gate scanners read Aztec, but phone camera apps often do not. Public-facing codes should stay QR: see QR vs Aztec for the full comparison.

FAQ

Is the code on my boarding pass a QR code?

Usually not: mobile boarding passes and rail e-tickets are typically Aztec codes, recognisable by the single square bullseye at the centre rather than three corner squares.

Can a phone camera scan an Aztec code?

Inconsistently. Some camera apps and libraries support it, many do not. Aztec's home is closed ticketing systems where the operator controls the scanner.

Why does Aztec not need a quiet zone?

Its finder is a central bullseye rather than edge patterns, so the decoder locks on from the middle outward and never needs contrast at the symbol's boundary.