GLOSSARY
The words, defined once.
Every GS1 term the product uses — one plain sentence, then a paragraph, and a source for each. These are the same definitions the app shows when you hover a term, not a second set written for a marketing page.
Application identifier (AI) 01 · 10 · 21
The two-to-four-digit code in front of a value that says what the value means — 01 is a GTIN, 10 a batch, 21 a serial number.
GS1 data is self-describing: every value is preceded by a number that names it. That number is the application identifier. It is why a machine reading a code does not need to be told what the digits after it are, and it is why the parts of a Digital Link URI can never be reordered — the identifier and the value are one unit, and the path is a sequence of those units.
GS1 General Specifications PDF https://ref.gs1.org/standards/genspecs/
Check digit
The last digit of a GTIN, computed from the digits before it, so a mistyped number can be caught before it is printed.
A check digit is arithmetic, not a lookup: multiply the other digits by an alternating weighting, sum them, and the check digit is what takes the total to the next multiple of ten. It catches every single-digit mistake and most transpositions. It is the reason an import can tell you a number is wrong without knowing anything about your products, and the reason a barcode scanner does not silently return a different product when one bar is misread.
GS1 General Specifications PDF https://ref.gs1.org/standards/genspecs/
GS1 Company Prefix
The block of digits GS1 licenses to your company; every GTIN you issue begins with it, which is what makes your numbers yours.
You license a prefix from your local GS1 member organisation, and its length decides how many GTINs you can issue underneath it — a shorter prefix leaves more digits for products. Prefixes are licensed rather than sold, and are renewed annually. A single GTIN can also be bought outright for one product without a prefix, which is often the right first step for a brand with one SKU.
GS1 US — GS1 Company Prefix https://store.gs1us.org/gs1-company-prefix/p
Consumer product variant (CPV) 22
A qualifier for a version of a product a shopper can tell apart but that does not warrant a different GTIN.
Some differences matter to a person holding the pack and not to a supply chain: a seasonal sleeve, a promotional flash, a recipe tweak that changes nothing on the nutrition panel. The consumer product variant is where those live. It sits between the GTIN and the batch in the fixed qualifier order, so a link defined for one variant does not disturb the links defined for the product as a whole.
GS1 Digital Link Standard: URI Syntax https://ref.gs1.org/standards/digital-link/uri-syntax/
GS1 Digital Link URI /01/{gtin}/10/{lot}
A web address that carries a GTIN in a structured path, so one printed code both identifies the product and points at information about it.
The structure is fixed: a domain you choose, then the primary identifier and its value, then any qualifiers in a defined order, with data attributes in the query string. Because the GTIN is in the path rather than hidden in a short link, a point-of-sale system can read the number without following the address at all — which is what lets a single symbol serve both the checkout lane and the shopper's phone.
GS1 Digital Link Standard: URI Syntax https://ref.gs1.org/standards/digital-link/uri-syntax/
Error correction
Redundant data inside a symbol that lets a scanner still read it when part of the printed code is scuffed, folded or under-inked.
QR Code offers four levels — roughly 7%, 15%, 25% and 30% of the symbol recoverable — and the level is a choice, traded against how much data fits in the same area. Data Matrix has one level, ECC200, at roughly 30%. More correction is not automatically better: it makes the symbol denser at the same physical size, and a denser symbol needs a larger X-dimension to stay readable.
GS1 General Specifications PDF https://ref.gs1.org/standards/genspecs/
Global Product Classification (GPC)
GS1's scheme for saying what kind of thing a product is, as distinct from which product it is.
GS1 describes it as a system that gives buyers and sellers a common language for grouping products in the same way, everywhere in the world. A GTIN identifies one product; a GPC category says what category that product belongs to, in terms a trading partner on the other side of the world uses too. It is what a retailer's system means when it asks which classification your item sits in. A product in packagepage can carry a GPC category, and nothing here requires one — it is a field you fill in when a trading partner asks you for it.
GS1 standards repository — Global Product Classification https://ref.gs1.org/standards/
Grain gtin · batch · serial
Our word, not GS1's, for the level a link is defined at: the product, one batch of it, or one individual unit.
GS1 has the qualifiers; we needed a single noun for what they pick out, because almost everything the product does depends on it. A link defined at the product level is inherited by every batch and every unit beneath it. A link defined at the batch level shadows the product-level link of the same type — and only of the same type, which is why publishing a recall notice has to write two links rather than one. When you see 'grain' in the product, this is what it means; you will not find the word in a GS1 document.
packagepage — our own vocabulary, not a GS1 term
GTIN 01
The number that identifies a product — the thing every barcode has always carried, and the part of a 2D code that must never change.
A GTIN identifies a trade item: a specific product in a specific pack size. It is the number underneath an EAN-13 or a UPC, and it is the number inside a 2D code's web address. In a Digital Link URI it is always written as fourteen digits, with shorter forms padded on the left with zeroes, so that one length works everywhere. GTIN is a GS1 trademark and a data type — it is never a brand or a product name.
GS1 General Specifications PDF https://ref.gs1.org/standards/genspecs/
Link type gs1:pip
The label on a link that says what is at the other end, so a machine can ask for one kind of answer specifically.
A product page, allergen information, a recall notice and an instruction manual are four different answers to the same scan, and the link type is how a request says which one it wants. GS1 publishes the vocabulary; a resolver that is asked for a type it does not have answers with a 404 rather than quietly returning something else. One type per identifier is marked as the default — the one a phone camera gets when it asks for nothing in particular.
GS1 Web Vocabulary — link types JSON https://ref.gs1.org/voc/data/linktypes
Linkset application/linkset+json
The whole list of links attached to one identifier, returned as JSON so a system can read every answer at once instead of following a redirect.
A phone camera wants one destination. A retailer's system, a regulator's crawler or your own integration usually wants the map. Asking a conformant resolver for the linkset — by query parameter or by content negotiation — returns every link it holds for that identifier, each with its type and any language or media it is scoped to, in the format RFC 9264 defines.
GS1-Conformant Resolver Standard https://ref.gs1.org/standards/resolver/
Qualifier 22 · 10 · 21
An identifier that narrows a GTIN to something more specific — a consumer variant, a batch or a single unit — in a fixed order.
The order is not a convention, it is normative: consumer product variant, then batch or lot, then serial number. A URI may stop at any point in that sequence but may not skip a step out of order. That fixed shape is what lets a resolver reason about specificity — it can tell that a request for a serial number sits underneath a batch, which sits underneath the product, without knowing anything about your catalogue.
GS1 Digital Link Standard: URI Syntax https://ref.gs1.org/standards/digital-link/uri-syntax/
Quiet zone
The empty margin a scanner needs around a symbol to find its edges: four modules on every side for QR Code, one for Data Matrix.
The quiet zone is part of the symbol, not the space around it, and it is the single most common reason a code that looks fine fails on press. Artwork that crowds it — a rule, a fold, the edge of the label — makes a code that reads on a desk and fails on a pallet. It is measured in modules rather than millimetres, so it scales with the X-dimension and has to be recalculated whenever the symbol is resized.
GS1 General Specifications PDF https://ref.gs1.org/standards/genspecs/
Resolver
The service a scanned Digital Link URI reaches, which decides which link the scanner should get and sends it there.
It is the piece that makes a printed code editable after it is printed. The code carries an address; the resolver decides what that address currently answers, and it can change that answer without anyone reprinting anything. Because packaging outlives software, a resolver's only real requirement is that it keeps answering — which is why ours holds its read model on every node and needs no database on the path a scan takes.
GS1-Conformant Resolver Standard https://ref.gs1.org/standards/resolver/
X-dimension
The width of one module — the smallest square in a 2D symbol — in millimetres.
It is the number that decides whether a code works at a checkout lane, and it is not a matter of taste. For retail point of sale, a 2D symbol's X-dimension must be 1.5× the X-dimension of the equivalent linear barcode; the tables that give the equivalents live in the GS1 General Specifications, and the value depends on the symbology and the application. A symbol that scans on your phone at any size can still be too small for a lane, and you will not find out until the labels are on pallets.
2D Barcodes at Retail Point-of-Sale Implementation Guideline https://ref.gs1.org/guidelines/2d-in-retail/