Global Trade Item Number (GTIN) is an identifier for trade items, developed by GS1. Such identifiers are used to look up product information in a database (often by entering the number through a barcode scanner pointed at an actual product) which may belong to a retailer, manufacturer, collector, researcher, or other entity. The uniqueness and universality of the identifier is useful in establishing which product in one database corresponds to which product in another database, especially across organizational boundaries.

The GTIN standard has incorporated the International Standard Book Number (ISBN), International Standard Serial Number (ISSN), International Standard Music Number (ISMN), International Article Number (which includes the European Article Number and Japanese Article Number) and some Universal Product Codes (UPCs), into a universal number space.

GTINs may be 8, 12, 13 or 14 digits long, and each of these four numbering structures are constructed in a similar fashion, combining Company Prefix, Item Reference and a calculated Check Digit (GTIN-14 adds another component- the Indicator Digit, which can be 1-8). GTIN-8s will be encoded in an EAN-8 barcode. GTIN-12s may be shown in UPC-A, ITF-14, or GS1-128 barcodes. GTIN-13s may be encoded in EAN-13, ITF-14 or GS1-128 barcodes, and GTIN-14s may be encoded in ITF-14 or GS1-128 barcodes. The choice of barcode will depend on the application; for example, items to be sold at a retail establishment could be marked with EAN-8, EAN-13, UPC-A or UPC-E barcodes.

The EAN-8 code is an eight-digit barcode used usually for very small articles, such as chewing gum, where fitting a larger code onto the item would be difficult. Note: the equivalent UPC small format barcode, UPC-E, encodes a GTIN-12 with a special Company Prefix that allows for "zero suppression" of four zeros in the GTIN-12. The GS1 encoding and decoding rules state that the entire GTIN-12 is used for encoding and that the entire GTIN-12 is to be delivered when scanned.