What is a GTIN? Formats, check digits, and when you need one

What a GTIN is — and what it is not

GS1 describes a GTIN as a unique, global, verifiable product identifier issued by GS1. The brand owner assigns one GTIN to each distinct trade item it sells, using a GS1 licence, so the same number identifies the same product for every retailer, distributor, and marketplace worldwide.

A GTIN is data; a barcode is the carrier that encodes it. A UPC-A barcode carries a 12-digit GTIN, an EAN-13 barcode carries a 13-digit GTIN, and the digits printed under the bars are the GTIN itself. That is why “UPC” and “EAN” are used loosely to mean the number.

A GTIN also does not tell you where a product was made. GS1 states that its prefixes do not identify a product’s country of origin — they only show which GS1 Member Organisation issued the number range.

The four GTIN formats: GTIN-8, GTIN-12, GTIN-13, and GTIN-14

Every GTIN has 8 to 14 digits, the last being a check digit. A shorter GTIN can be left-padded with zeros to 14 digits without changing what it identifies; GS1 US guidance advises storing all four formats in a 14-digit field. For 12-digit GTINs there is an implied leading zero, which is why the GS1 Prefix of 614141234561 is 061, not 614.

How the GTIN check digit works (with a worked example)

The final digit of every GTIN is calculated from the others using a modulo-10 algorithm. It catches typing and scanning errors such as a wrong digit or most swaps of neighbouring digits. GS1’s manual method works for all four formats.

Here is GS1’s own GTIN-13 example. The first twelve digits are 6 2 9 1 0 4 1 5 0 0 2 1, and we want the thirteenth.

1. Write down the digits without the check digit: 6 2 9 1 0 4 1 5 0 0 2 1.
2. Starting from the rightmost digit (the one just left of the check digit), multiply alternately by 3 and 1. Working back to the left, the multipliers for this number are ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3 ×1 ×3.
3. Multiply each digit: 6, 6, 9, 3, 0, 12, 1, 15, 0, 0, 2, 3.
4. Add the results: 6 + 6 + 9 + 3 + 0 + 12 + 1 + 15 + 0 + 0 + 2 + 3 = 57.
5. Subtract the sum from the nearest equal or higher multiple of ten: 60 − 57 = 3. The check digit is 3, so the full GTIN is 6291041500213.
6. To validate an existing GTIN, repeat the calculation on every digit except the last and compare. A GTIN-12 example: 61414123456 gives a sum of 89, so the check digit is 90 − 89 = 1 and the full number is 614141234561.

What a valid check digit does — and does not — prove

Because the multipliers are counted from the right, adding leading zeros never changes the check digit. 614141234561 and its 14-digit form 00614141234561 validate identically, which is what makes 14-digit storage safe.

A correct check digit proves only that the number is well formed. It does not prove the GTIN was licensed to the brand, that it is assigned to this product, or that it is not already used elsewhere. Google Merchant Center requires a correct check digit but also tells sellers not to guess or invent GTIN values. Treat the check as a typo filter, then confirm the number against the brand’s documents.

How to get GTINs — and why resold barcodes are risky

If you are the brand owner — you sell products under your own brand, including private label — the GTINs are yours to assign. You need a GS1 Company Prefix before you can create GS1 identification keys, and you license it from the GS1 Member Organisation in your country. GS1 has member organisations in more than 120 countries.

Pricing and options differ by country. As an example, GS1 US lists a single GTIN as a one-time purchase with no renewal fee, and Company Prefixes for 10 to 100,000 items with an up-front fee and annual renewal. If a prefix licence lapses, GS1 US says you are no longer authorised to use the numbers from that prefix.

Avoid cheap “UPC” or “EAN” numbers from resellers. GS1 Australia, a GS1 Member Organisation, states that GS1 has no relationship with these resellers and that a resold number is no longer managed by GS1, with no guarantee it will remain unique. GS1 does not recognise resold numbers, and they may not be unique or attributed to you — a channel that checks GTINs against GS1 company data can see the prefix belongs to another company.

1. Check whether a GTIN already exists. If you resell another brand’s product, use the manufacturer’s GTIN from the pack or the supplier’s data sheet; you do not create your own.
2. Contact your local GS1 Member Organisation and choose between individual GTINs and a Company Prefix, based on how many products, variants, and pack sizes you expect.
3. Build the GTINs: Company Prefix, then your item reference, then the check digit.
4. Assign one GTIN per distinct trade item — every style, colour, and size variant, and every packaging level above the consumer unit.
5. Publish the GTIN in the identifier field of each sales channel and print the matching barcode on the pack.

GTIN vs UPC vs EAN vs SKU vs MPN vs ISBN

Three of these are GTINs; the other three are separate codes with different owners and scope. Most channels want the GTIN plus the brand, and the manufacturer part number where there is no GTIN.

When you need a new GTIN

The GS1 GTIN Management Standard sets ten rules for when a change to a product requires a new GTIN: new product introduction, declared formulation or functionality, declared net content, dimensional or gross weight change, adding or removing a certification mark, primary brand, time-critical or promotional products, pack or case quantity, predefined assortments, and price on pack.

The table covers the rules most sellers run into. For the others, read the conditions in the GS1 standard before deciding.

Where sales channels use GTINs

Each channel stores the GTIN in a different field and reacts differently when it is missing.

• Google does not accept GTINs with restricted prefixes (02, 04, and 2) or coupon prefixes (05, 98, and 99) as product identifiers.
• In Shopify’s product CSV the column is now Barcodes; separate multiple values with semicolons and optionally add a type prefix such as gtin:.
• In the WooCommerce REST API (v3) the core field is global_unique_id. Since WooCommerce 11.2, CSV update imports fall back to matching on this column only when both ID and SKU are blank.
• On eBay, one GTIN can map to several catalog products, so eBay’s Inventory API prefers an eBay product ID (ePID) for catalog matching where you have one.

What to do when a product has no GTIN

Some products legitimately have no GTIN: custom and handmade goods, antiques, and items made before GTINs existed. Do not invent a number to fill the field. Each channel has a defined way to say the product has none.

• Google Merchant Center: provide brand and MPN where they exist. Set identifier_exists to no only for products that genuinely have no GTIN, MPN, or brand; Google warns if it finds evidence an identifier exists.
• eBay: select “Does not apply” for the identifier when the item has none. The exact text varies by eBay marketplace.
• Amazon: Amazon says sellers without a GTIN may be eligible for a GTIN exemption. The application asks for a product name or title and images showing all sides of the product and its packaging.
• Shopify and WooCommerce: leave the barcode or GTIN field empty rather than filling it with a SKU, which can confuse downstream feeds.

GS1 Digital Link and 2D barcodes

GS1 Digital Link is a standard way to express GS1 identifiers — GTIN, batch, serial number, expiry date, and more — as a web address. Encoded in a 2D barcode such as a QR code, one symbol can be scanned at the till and also open web content, and the brand can change where the link points without reprinting the pack. In healthcare, GS1 notes that GS1 DataMatrix is used instead.

In the US, GS1 US has set a 2027 “Sunrise” target for retail point-of-sale systems to be able to read 2D barcodes. GS1 US says it is not necessary to implement every 2D capability by that date, and Sunrise 2027 is an industry readiness target rather than a legal deadline. Brands are encouraged to make sure existing QR codes follow GS1 Digital Link and include the GTIN. The GTIN itself does not change: a 2D barcode is another carrier for the same number.

The schema.org gtin property likewise accepts either the digits or a GS1 Digital Link URL.

Getting GTINs right in supplier documents and product data

If you resell other brands, the GTIN comes from your supplier. It usually appears in a product data sheet, a price list, or the ordering and logistics section of a catalog — often next to the article number, with separate codes for the single unit and the case.

For large supplier catalogs, Doc2Shelf can read the PDFs and extract identifiers such as GTIN, EAN, and MPN alongside the other product data, with a confidence score for each extraction and the source page and quote for each extracted fact, so a person can check them against the source before the data reaches a listing.

• Store GTINs as text, never as numbers: spreadsheets drop leading zeros and turn long values into scientific notation.
• Keep the unit GTIN and the case GTIN in separate fields; a GTIN-14 case code is not meant for point-of-sale scanning and is usually the wrong identifier for a single-unit listing.
• Map each GTIN to the exact variant row it belongs to — colour and size variants each have their own.
• Run a check-digit test on every value after import, and re-check any value that fails against the original document.
• Flag duplicates: the same GTIN on two different products in your catalog is almost always an error.