GTIN, submitted as <g:gtin> in Google Merchant Center feeds and gtin in Meta Catalog, is the globally unique product identifier assigned by the manufacturer -- most commonly a 12-digit UPC, 13-digit EAN, or 8-digit JAN -- that lets Google and Meta match a listing against their own product catalogs. It's a plain numeric string with no dashes or spaces, such as 00196565113317, and it's the single most important identifier field in a modern Shopping feed.

Why It Matters

Google uses GTIN to link a merchant's listing to its broader product catalog, which unlocks richer Shopping results, product ratings pulled from other retailers, and eligibility for certain ad formats that identifier-less listings can't access. Missing or malformed GTINs are consistently one of the top rejection reasons in Merchant Center diagnostics, and Google has progressively tightened enforcement so that most new items in GTIN-mandatory categories, like consumer electronics and media, are disapproved outright without one. Because GTIN plus brand is treated as a de facto identity for a product, getting it wrong doesn't just risk disapproval -- it can also cause a listing to be matched against the wrong catalog entry, surfacing incorrect reviews or specs to shoppers.

How It Works

When a manufacturer has assigned a GTIN, Google and Meta both require it to be submitted; when a product genuinely has none, such as many private-label or made-to-order goods, the feed should instead set identifier_exists to false and rely on brand plus mpn as the fallback identity pair. Google validates GTIN format and its checksum digit, rejecting strings of the wrong length or with an invalid final check digit, and does not accept ISBN-10 without conversion to its 13-digit GTIN equivalent. Meta Catalog follows the same acceptance rules -- UPC, EAN, ISBN, or JAN -- and similarly expects identifier_exists to be set explicitly rather than left blank when no code applies. Merchants who inherited a catalog with reused, truncated, or manufacturer-recycled GTINs often see a wave of disapprovals appear all at once when Google tightens validation, which is the exact failure mode walked through in Resolving GTIN Rejections and Identifier Errors for Google Shopping.

Example

<item>
  <g:id>SKU-77410</g:id>
  <title>Wireless Noise-Cancelling Headphones - Black</title>
  <link>https://example-shop.com/products/headphones-black</link>
  <g:price>199.00 USD</g:price>
  <g:gtin>00196565113317</g:gtin>
  <g:brand>Aurex</g:brand>
  <g:mpn>AX-NC200-BLK</g:mpn>
</item>

Related Concepts

GTIN works as a pair with brand, since Google cross-references both to confirm a catalog match, and it functions as the standardized alternative to MPN, which only carries meaning alongside the manufacturer's name. Feed teams should keep gtin distinct from any internal SKU value used purely for warehouse tracking -- the two serve different systems, and mixing them is a frequent source of identifier errors during feed migrations. Auditing GTIN coverage across a catalog before a major sync, rather than after Google flags the gaps, is one of the cheapest ways to protect Shopping visibility ahead of a peak season.