Product identifiers are the standard codes that tell an ad network exactly which product you're advertising: a GTIN (the barcode — EAN, UPC, or ISBN), the brand that makes it, and the MPN (the manufacturer's part number). Networks use them to match your product to the same item elsewhere and rank it, so missing ones cost you reach.
What each product identifier is#
The three identifiers work together, from most specific to least:
GTIN — the barcode#
A GTIN (Global Trade Item Number) is the barcode number printed on a product's packaging. You'll usually know it by its regional name — an EAN in Europe, a UPC in North America, or an ISBN on books. It's the strongest identifier because it points at one exact manufactured product, the same everywhere it's sold.
Brand — who makes the product#
The brand is the maker or label the product is sold under. Almost every product has one, and it's the identifier ad networks lean on when there's no barcode.
MPN — the manufacturer's part number#
The MPN (manufacturer part number) is the maker's own internal code for the item. On its own it isn't unique across the market, but paired with the brand it names a specific product — which is why the two are quoted together as a fallback when a barcode is missing.
Why ad networks use product identifiers#
Ad networks like Google, Meta, and TikTok use identifiers to recognize which product you're advertising and connect it to the same item across the web. That matching does two things for you:
- It makes your product eligible. When a network can confidently identify your product, your listing can carry the right details and show for the right searches. A product it can't identify is harder to place — and often reaches fewer people.
- It helps your product compete. Once a network can match your item to the same product elsewhere, it can rank and surface it properly against competing listings. Good identifiers put your product in that competition; missing ones leave it out.
In short: identifiers are how a network trusts what your product is. The better it can identify a product, the further that product tends to reach.
When product identifiers are required — and when they're exempt#
The general rule — closest to how Google states it — is straightforward: if a product has a GTIN, provide it; if it genuinely doesn't, provide the brand plus MPN together instead. [VERIFY: exact identifier requirement and GTIN-vs-brand+MPN fallback rule per network — Google, Meta, TikTok.]
Some products genuinely have no barcode, and networks don't expect you to invent one:
- Custom-made, handmade, or made-to-order products.
- Vintage, antique, or one-of-a-kind items.
- Your own-brand products that were never assigned a manufacturer barcode.
For those, networks let you declare that no identifier exists rather than forcing a GTIN. The exact exempt categories, and the setting used to say a barcode doesn't exist, are each network's own policy. [VERIFY: Google Merchant Center identifier-exemption categories and the "identifier exists" setting.] [VERIFY: Meta and TikTok identifier requirements and exemptions by category.]
One thing that surprises people: a well-formed barcode can still be wrong. Every GTIN, EAN, and UPC ends in a check digit calculated from the rest of the number, so a typo or a truncated value produces an invalid barcode — and networks like Google check the number against their own product registry on top of that. A structurally valid barcode that names the wrong product will still be rejected. [VERIFY: Google's GTIN validation against its product registry and rejection of well-formed-but-mismatched barcodes.]
Are identifiers required in Renable?#
No — and this is worth knowing. Identifiers are recommended, not required in a catalog. Renable's seven required fields are ID, title, description, URL, main image, price, and availability, so a catalog won't flag a product as missing a GTIN, brand, or MPN. The ad network is what limits reach for products without them, not Renable. This is why a product can pass every check in Renable and still under-deliver on Google or Meta for a missing identifier.
How you add and fix identifiers in Renable#
Identifiers live in the Identity group on a catalog's Mapping tab, and there are three ways to fill them:
- Map a column you already have — if your feed carries a barcode, brand, or part-number column, point the matching catalog field at it on the Mapping tab.
- Set a value with a rule — when a value is constant or derivable (a single-brand store, a fixed MPN prefix), a Set field rule writes it.
- Pull one in from another feed — when your main feed lacks barcodes but a supplier feed has them, a lookup joins the two feeds and brings the GTIN across.
The full step-by-step for all three is in Add missing product identifiers — this glossary entry explains what the identifiers are; that article covers how to fill them.
FAQ#
My products don't have barcodes — what do I use instead of a GTIN?
Provide the brand and MPN together; most ad networks accept that pairing as the identifier for a product that has no GTIN [VERIFY: exact brand+MPN fallback requirement per network]. For products that genuinely have no barcode — custom-made, handmade, vintage, or your own brand — networks let you declare that no identifier exists rather than inventing one.
Do I need all three of GTIN, brand, and MPN on every product?
Generally you provide a GTIN whenever the product has one, and fall back to brand plus MPN when it doesn't. Brand is worth setting on nearly every product regardless. Exact per-network and per-category requirements vary [VERIFY: Google, Meta, and TikTok identifier requirements by category].
I added a GTIN but the ad network still rejects it — why?
Two common causes. First, a barcode whose check digit doesn't add up — a typo or a value cut short — imports but is dropped before your feed reaches any ad network, so it arrives as missing. Second, a well-formed barcode that doesn't match the product the network has on record. See Fix products disapproved by Google.
Related articles#
- Add missing product identifiers — the three ways to fill a GTIN, brand, or MPN.
- Fix products disapproved by Google — when a missing or invalid identifier gets a product rejected.
- Joining another feed — pull a GTIN in from a supplier feed with a lookup.