Catalog fundamentals: ASINs, SKUs, and product identity

Seller SKU — yours. A reference of up to 40 characters that you define once and never change. It identifies your offer on a product, not the product itself: two sellers on the same ASIN will each have their own SKU. Keep it consistent with whatever your source of truth is (an ERP, a master spreadsheet), because every flat file, report, and support case will refer to it.

GTIN (UPC / EAN / ISBN) — the standards body's. The barcode number issued through GS1. Amazon validates GTINs against the GS1 database, so a code that was not licensed to your brand can be rejected outright. The GTIN pins down the physical item: a 750 mL bottle and a 500 mL bottle of the same design have different GTINs, and so do a single unit and a 2-pack.

ASIN — Amazon's. A ten-character catalog identifier (most start with B0) that Amazon assigns when a detail page is first created. It is shared by everyone who sells that product. You never choose it; you either match an existing one or trigger the creation of a new one.

The detail page is shared catalog content: title, bullet points, description, images, and every attribute. It is assembled from contributions by all sellers of the ASIN, the brand owner, and Amazon itself. When contributions disagree, Amazon ranks them — a Brand Registry owner generally outranks a reseller, and Amazon's own data can outrank both. This is why an edit that processes without errors can still fail to appear on the page: someone else's contribution won.

Your offer is everything that is only about you: price, quantity, condition, fulfillment channel, handling time. Offers compete for the Featured Offer (the "Buy Box"); they never change what the detail page says.

Practical consequence: when a page shows wrong content, first ask whose contribution is showing. If it is not yours, the fix is Brand Registry authority or a support case with evidence — not another upload.

Amazon prohibits duplicate detail pages, so the first move in Catalog → Add Products is always a search by GTIN (or ASIN). If an exact match exists, you add your offer to it. If nothing matches, you create the page.

"Exact" means the same product in the same configuration:

• same GTIN,
• same size, capacity, color, flavor, or edition,
• same pack count and unit count,
• same brand.

A page that shares the brand, the design, and the photo but differs in any one of those is a different product. Matching to it creates a detail page that misdescribes what customers receive — the fastest route to returns, negative reviews, and a suppressed listing.

Beyond the visible fields, each listing carries attributes that shoppers never see but Amazon's systems act on:

• Product type and browse node decide which category the item lives in, which attributes are required, and which variation themes are allowed.
• Generic keywords (backend search terms) add search coverage the visible copy does not have.
• Compliance fields — batteries, hazmat, country of origin, unit count, age range — are required per product type; a missing one can suppress the listing silently.
• Item type keyword, target audience, and material feed filters and recommendations.

The Category Listing Report (Reports → Inventory Reports) exports every one of these attributes for every SKU, which makes it the standard base for audits and bulk edits.

• Catalog → Add Products — match or create a listing, one product at a time.
• Catalog → Add Products via Upload — bulk creation and updates with flat files, plus the processing reports.
• Inventory → Manage All Inventory — edit live listings, filter by status (Active, Inactive, Incomplete, Search suppressed).
• Reports → Inventory Reports — the Category Listing Report and All Listings Report.
• Performance → Account Health — policy issues that can take listings down, including product-identity complaints.