The Aztec code is a kind of 2D barcode, encoding machine-readable data as an image.
An Aztec code is recognizable by the central "bullseye" pattern in the center of a square (reminiscent of an Aztec pyramid viewed from above). It is standardized by ISO/IEC 24778:2008. The encoding, and essential principles of the decoding, are in the public domain.
Here is "Hello, world!" as an Aztec code:
