Composite symbologies are a class of bar code symbology, the principal distinguishing feature of which is that they comprise two, or more, components, each of which is a distinct symbol, but which contain a set of related data. Typically one component is a linear symbol containing primary data, which can be read on its own in some areas of the application. The other component(s) is a two-dimensional symbol containing supplementary data which qualifies the primary message, and requiring all components to be read to extract the complete message. The GS1 Composite symbology is one such symbology. The use of the symbology is intended to comply with the GS1 General Specifications.

A GS1 Composite symbol consists of a linear component (encoding the item's primary identification) associated with an adjacent 2D component (encoding supplementary data, such as a batch number or expiration date). The GS1 Composite symbol always includes a linear component so that the primary identification is readable by all scanning technologies, and so that 2D imagers can use the linear component as a finder pattern for the adjacent 2D component. The GS1 Composite symbol always includes a multi-row 2D component, for compatibility with linear and 2D imagers, and with linear and rastering laser scanners.

GS1 Composite symbols are intended for encoding identification numbers and data supplementary to the identification in accordance with the GS1 General Specifications. The administration of the numbering system by GS1 ensures that identification codes assigned to particular items are unique world-wide and that they and the associated supplementary data are defined in a consistent way.

ISO/IEC 24723:2010 defines the requirements for the GS1 Composite symbology. It specifies the GS1 Composite symbology characteristics, data character encodation, symbol formats, dimensions and print quality requirements, error correction rules, and reference decoding algorithms. For those linear and 2D components of GS1 Composite symbols with published symbology specifications, those published specifications apply, except as specifically noted in ISO/IEC 24723:2010.