Where to find a SKU number

Three numbers that get mixed up

A product in a store carries up to three kinds of number, and only one of them is printed on the box. The GTIN, which is the UPC or EAN under the barcode, belongs to the product and is the same wherever it is sold. The SKU belongs to one seller, who invented it for its own stock system, so two shops selling the same item have two different SKUs. The platform code, such as an Amazon ASIN or a Walmart item number, belongs to a listing on that platform.

Amazon and Walmart both say the number above or below the barcode is the product ID. Walmart goes further and refuses SKU and model numbers as product IDs, because they are not universal. So if you are looking at a package, the number you can see is most likely the GTIN, and the SKU is somewhere else.

Finding a SKU as a shopper

Start with the shelf tag or price label, since many stores print their own SKU there. Then check the receipt and the order confirmation email. Online stores that show SKUs put them in the order summary, in your order history, or near the bottom of the product description. Pokémon Center's support page is a good example of how a store that does this lays it out. The SKU sits under the product name in the order email, prefixed by SKU #. It sits in the same place under My Account and Order History.

Many stores never show a SKU at all: eBay and Google Merchant Center hide it from buyers by design. Shopify stores show it only when the shop adds code or an app. Amazon says SKUs do not always appear on product listings. If you need to identify an item for a return or a reorder, the GTIN or the model number will usually do the job better.

Finding a SKU as a seller, platform by platform

Where each platform keeps the SKU

Platform	What the field is called	Where it is	Who sees it
Shopify	SKU, on each product variant	Products, the product, the variant, then the Inventory section	Internal by default; the storefront shows it only with custom code or an app
Amazon	SKU	Inventory, then Manage All Inventory lists every active SKU; Catalog, Add Products has the SKU field when you list	Not always shown on listings; Amazon assigns a SKU if you leave the field blank
eBay	Custom label (SKU)	An optional field on the listing form and a column in Seller Hub upload templates	The buyer does not see it
Etsy	SKU	Edit the listing, scroll to Inventory and pricing	Not stated on Etsy's help page
Google Merchant Center	id	The required id attribute in your product feed, which Google recommends filling with your SKU	Not shown to customers
Meta catalogs for Facebook and Instagram	id, shown as Content ID	The catalog feed, where Meta says to use the item's SKU if possible	Not stated

Shopify adds one detail worth knowing: a barcode scanner at the till reads the variant's barcode field, not the SKU. So the two fields do different jobs. Amazon says much the same. It says most products on Amazon have an ASIN, a GTIN and a SKU, and only the SKU is used for your own inventory.

Limits and rules per platform

eBay allows a SKU of up to 50 characters, or 80 on a variation. Google's id field takes 1 to 50 characters, and Meta's content ID up to 100. Etsy recommends 4 to 8 characters and suggests avoiding the letters O and I and symbols such as commas or slashes. Shopify advises no more than 16 characters and treats ABC123 and abc123 as different SKUs.

Google also says where a SKU must not go. If your products have no manufacturer identifiers, leave the gtin, brand and mpn fields empty rather than putting a SKU in them. The one exception is a store brand, where Google lets you put your own identifier, such as the SKU, in the mpn field.

Finding one SKU among thousands

Each platform has a search that takes a SKU. In Shopify, the admin search bar and the POS app both find a variant by SKU. On Etsy, the search bar in the Listings section of Shop Manager does the same. On Amazon, Manage All Inventory can be filtered by SKU. Keeping the same SKU on every platform makes this quick, because one code then pulls up the same product everywhere.

If a product has no SKU yet, make one that starts with a letter and stays short, as what a SKU is explains. The SKU generator builds a whole list from your product options. It draws any code as a Code 128 barcode for a shelf or bin label.

The number that is on the package is the GTIN, and where the UPC code is on a product shows how to read it. To print your own SKU labels from a spreadsheet, how to make a barcode in Excel covers the label route.