Product Identifier

It helps to group product identifiers by who owns and controls them. The GTIN is the universal layer: issued by GS1, globally unique, and recognised by every retailer and marketplace — this is what a UPC, EAN, or ISBN encodes. The MPN is the manufacturer layer: the part number a maker assigns, unique only when paired with the brand name.

Then there are platform and internal identifiers. The ASIN is Amazon's own code for a catalogue page, meaningful only inside Amazon. The SKU is your private code, meaningful only inside your business, used to track stock and orders. The same physical product can carry all four at once — one GTIN, one MPN, one ASIN per Amazon marketplace, and one SKU per seller — because each answers a different question.

Match the identifier to the task. To match your offer to a marketplace catalogue or run a shopping feed, you need the GTIN — it is the only identifier every platform recognises. To help buyers find an exact spare part, surface the MPN. To advertise or report on Amazon, work with the ASIN. To track inventory and fulfilment internally, use the SKU.

Most marketplaces and Google Shopping require a GTIN where one exists, and accept the combination of brand plus MPN as a fallback for products that genuinely have no barcode. Where neither applies — handmade or bundled goods, for instance — a GTIN exemption may be needed. The clearest mental model is a stack: GTIN for the world, MPN for the manufacturer's catalogue, ASIN for Amazon, SKU for you.

Problems in multichannel selling almost always trace back to identifiers that drift out of sync. If your SKU points to the wrong GTIN, or an offer attaches to the wrong ASIN, you get mismatched listings, wrong stock counts, and customer complaints. The fix is a single source of truth that maps each product's SKU, GTIN, MPN, and per-marketplace ASINs together.

When that mapping is clean, inventory and price sync across channels becomes reliable: the system matches on your SKU, knows the GTIN that identifies the product everywhere, and can reconcile the Amazon ASIN without ambiguity. Treating product identifiers as a coherent set rather than isolated fields is what keeps a catalogue accurate as you scale across many marketplaces.