Stall library · Evaluate
Products have no GTIN or MPN to match against
A missing identifier means your products carry no GTIN, barcode or MPN, so an AI agent cannot confirm that the item on your page is the same item a shopper named somewhere else. The agent is left matching on titles, and a title match is a guess it may decline to make when a competitor has published the number.
Why the agent stops
Identifiers are how a product becomes the same product across sites. A shopper who names a model, or who saw the item elsewhere, gives the agent a string it must resolve to something in your catalogue. With an identifier that resolution is exact. Without one it is fuzzy text matching against your merchandising titles.
This is quietly decisive in comparison, because a store that can be matched exactly is a store that can be included in a price comparison at all.
How often we see this
Not stated here. A frequency means nothing without the cohort it was counted over, and this page is about one stall rather than one category. Where a category has enough stores measured at every stage, the share of them showing this stall is published on its benchmark page, with the methodology beside it.
See it for yourself
- Open your feed or a product page JSON-LD and look for gtin, gtin13, mpn or a barcode field.
- Check it is populated per variant, not only on the parent product. Different sizes usually have different barcodes.
- For own brand products with no manufacturer number, check whether an MPN or SKU is exposed at all.
What to change
- Populate the barcode field (GTIN, EAN or UPC) on each variant, which most platforms already have a field for.
- For own brand goods with no GTIN, publish a stable MPN and use it consistently everywhere you list.
- Expose the identifier in both the feed and the page structured data.
- Keep identifiers stable across catalogue migrations. An identifier that changes is close to no identifier.
What Ottom looks at
Ottom checks identifiers in your catalogue feed when the feed format carries them, and in your product page markup otherwise. Shopify and WooCommerce do not publish barcodes in the catalogue an agent can read, so on those platforms the page markup is what we read and what we report on. The finding is raised only when no product carries an identifier, which is the case where the gap is systematic rather than a data entry miss.
Questions
What identifier do I use if my products have no barcodes?
Publish a manufacturer part number of your own and keep it stable. The value of an identifier is not that it is registered with anybody, it is that the same product carries the same string wherever it appears: your product page, your feed, a marketplace listing, a comparison site. That property is what lets an agent decide two listings are one product, and it does not require a GTIN. Inventing one and then changing it is worse than having none.
Do missing GTINs stop an agent buying, or only finding us?
Mostly the second, which is why it sits in the evaluate stage rather than the buy stage. It changes whether you are in the comparison at all, not whether the checkout completes for somebody who has already chosen you. That is not a reason to deprioritise it: a purchase you were never considered for looks exactly like no purchase, and it leaves no trace in your analytics that anything happened.