A–Z barcode terms
This glossary covers the most common terms you’ll encounter when buying, printing, or validating barcodes. Definitions are kept concise with links to deeper articles where available.
Barcode
A machine-readable representation of data, typically shown as parallel lines (1D) or a matrix of dots/squares (2D). The pattern encodes numbers or characters that scanners decode into usable information.
Check digit
The final digit of a GTIN or other barcode number, calculated from the preceding digits using a weighted sum algorithm. It catches most single-digit errors and transpositions during manual entry or scanning. See also check digit calculator.
EAN (European Article Number)
A retail barcode symbology used worldwide outside North America. The standard form is EAN-13 (13 digits). EAN-8 is a compressed version for small packages. EAN-13 and UPC-A are technically compatible—most modern scanners read both. See GTIN overview.
GS1
The international not-for-profit organisation that administers the GS1 system of standards, including GTIN allocation. GS1 operates through national member organisations. See GS1 overview for how GS1-issued GTINs compare to reseller-issued GTINs.
GS1-128
A symbology derived from Code 128 that encodes GS1 Application Identifier data such as batch numbers, expiry dates, and serial numbers. Commonly used on logistics labels and healthcare products. Requires GS1-128-specific start character (FNC1).
GTIN (Global Trade Item Number)
The umbrella term for retail product identifiers: GTIN-8, GTIN-12 (UPC), GTIN-13 (EAN), and GTIN-14 (ITF-14). A GTIN uniquely identifies a trade item at a specific packaging level. See GTIN overview.
ISBN (International Standard Book Number)
A 13-digit GTIN-13 assigned to books, administered by the International ISBN Agency and national agencies. Prior to 2007, ISBNs were 10 digits; they now incorporate the 978 or 979 prefix ISBN Users’ Manual. ISBNs are valid GTINs and scan as EAN-13 barcodes.
ISSN (International Standard Serial Number)
An 8-digit identifier for serial publications (magazines, journals). For barcode use, ISSNs are typically converted to GTIN-13 by adding a 977 prefix and check digit recalculation.
ITF-14 (Interleaved 2 of 5, 14-digit)
A 14-digit GTIN used on shipping cartons and outer cases. Encoded in the Interleaved 2 of 5 symbology, which only represents numeric data. Always includes a GTIN-14 indicator digit (1–8 for packaging levels, 9 for variable measure). The ITF-14 barcode itself does not carry a check digit—the 14th digit is the GTIN check digit.
Quiet zone
The mandatory blank margin on either side of a barcode where no printing occurs. Scanners need this space to distinguish the barcode from surrounding graphics. Minimum quiet zone widths vary by symbology; for EAN/UPC it’s typically 7–11 module widths. Inadequate quiet zones are a leading cause of scan failures GS1 UK, Barcoding: Getting It Right.
Reseller GTIN
A GTIN purchased from a barcode reseller rather than obtained through direct GS1 membership. Reseller GTINs are legitimate numbers drawn from UCC-prefix allocations acquired before the year 2002 or from authorised pools. They are valid GTINs under GS1 standards but are not tied to ongoing GS1 membership fees. See GS1 overview for a balanced comparison.
Symbology
The specific encoding scheme that defines how data is represented in a barcode pattern. Each symbology has rules for character set, density, error detection, and physical dimensions. Common retail symbologies include EAN/UPC, Code 128, and Interleaved 2 of 5.
UPC (Universal Product Code)
The retail barcode symbology standardised for North American use. UPC-A encodes 12 digits (GTIN-12); UPC-E is a compressed 6-digit version for small packages. UPC-A and EAN-13 share the same scanning compatibility—UPC-A is effectively a subset of EAN-13 with a leading zero.
GS1 Digital Link
A specially structured URL that contains a GTIN. When paired with a resloved, the Digital Link URL can be followed to access additional product information. When a Digital Link is encoded into a barcode symbology such as a QR code, it can be scanned at Points of Sale just like any other product with a barcode. GS1 aims to have mass adoption of Digital Link Scanning in retailers by the end of 2027.
Resolver
A Digital Link resolver is an online service that redirects people following a GS1 Digital Link to information about the product being scanned. GS1 offers their own official resolver service, but the standard is open which allows anyone to create their own Digital Link resolver.
Quick comparison: retail identifiers
| Term | Digits | Symbology | Typical use |
|---|---|---|---|
| UPC-A | 12 | EAN/UPC | North American retail |
| EAN-13 | 13 | EAN/UPC | Global retail |
| EAN-8 | 8 | EAN/UPC | Small packages |
| ITF-14 | 14 | Interleaved 2 of 5 | Shipping cases |
| ISBN-13 | 13 | EAN/UPC | Books |
| ISSN (barcoded) | 13 | EAN/UPC | Serial publications |
Validation and verification tools
- GTIN validator and check digit calculator — verify number structure and calculate missing check digits
- GS1 GTIN definition — official GS1 reference
- International Barcodes Network — 120+ member reseller sites worldwide
- IBN Verified — barcode verification resources