The Aztec Code is a type of 2D barcode that was developed in 1995 by Andrew Longacre Jr. and Robert Hussey. It is distinguished by its central finder pattern, which resembles the eye of an Aztec pyramid, hence its name. This compact and efficient design allows the Aztec Code to encode a significant amount of data without requiring a surrounding blank "quiet zone," unlike other matrix barcodes. The code is constructed on a square grid with a bull's-eye pattern at its center, which facilitates locating the code. Data is encoded in concentric square rings around this central bull's-eye, with the size of the core and the number of layers determining the amount of data that can be stored.

The Aztec Code can encode up to 3,832 numerical digits, 3,067 alphabetic characters, or 1,914 bytes of data, making it highly versatile for various applications. It includes orientation marks in the corners, which allow the code to be read even if rotated or reflected, and the encoding process involves converting the source message into a string of bits, then computing the necessary symbol size and mode message. This process determines the Reed–Solomon codeword size, which is used for error correction, enhancing the code's reliability.

Due to its high data density and security features, Aztec Codes are commonly used in ticketing systems, such as rail tickets and airline boarding passes, and have found applications in tracking and authenticating items in manufacturing, logistics, government agencies, and healthcare. They are also well-suited for displays on mobile devices and are favored in situations where space is at a premium. The Aztec Code's design and capabilities make it a robust choice for modern data encoding and retrieval needs.