What Is an SKU?

An SKU (stock keeping unit) is an internal, alphanumeric code a seller assigns to each distinct product or variant to track it in inventory. Shopify defines it as "an alphanumeric retailer code for tracking inventory". Unlike a UPC barcode, which is universal and issued through GS1, you create your own SKUs and structure them however helps you find, count, and reorder stock.

What an SKU is

An SKU is a code that identifies one specific version of a product, down to the variant. A red t-shirt in size M gets a different SKU from the same shirt in size L, because they are separate items to count and sell.

It is alphanumeric and human-readable by design. A good SKU tells a staff member something at a glance, unlike a random barcode number.

You assign SKUs yourself, so they belong to your business and no one else's. Two shops can stock the identical item and label it with completely different SKUs.

The point of the code is control. It lets your store, your warehouse, and your reports all refer to the exact same item without confusion.

How to structure an SKU

A good SKU is built from meaningful segments, with the most important information first. Shopify notes that you "read a SKU from left to right", so put the key detail first, which makes a list of SKUs sortable and scannable.

Build each SKU from short codes for the attributes that matter: product type, then a distinguishing feature like color, then the variant like size. A plain hyphen keeps the segments readable.

A worked shape: a black t-shirt in medium becomes TSHIRT-BLK-M, and the same shirt in large becomes TSHIRT-BLK-L (illustrative example, not a standard). Anyone reading the code knows the product without opening a record.

Keep the scheme consistent across your whole catalog. Avoid spaces, avoid characters a spreadsheet might mangle, and never reuse an old SKU for a new product, or your stock history stops making sense.

SKU versus UPC, barcode, and GTIN

An SKU is internal and self-assigned, while a UPC, barcode, or GTIN is external and standardized. That is the core difference, and it is why a product carries both.

A UPC (Universal Product Code) is the barcode issued through GS1, the standards body, and it represents the manufacturer and the item. As Shopify puts it, "SKUs are for internal tracking needs, and UPCs are universal". A GTIN (Global Trade Item Number) is the wider international family that a UPC belongs to.

The practical split is who owns the code. You can invent your own SKUs freely, but you cannot self-issue a UPC, since those come through GS1 or the manufacturer.

	SKU	UPC / GTIN
Who assigns it	You, the seller	GS1, via the manufacturer
Scope	Internal to your business	Universal across all retailers
Format	Alphanumeric, your own scheme	Standardized numeric barcode
Same item at two shops	A different SKU at each	The same UPC everywhere
You can create it yourself	Yes	No

Source: Shopify, "What Is a SKU Number?" (shopify.com/blog/what-is-a-sku-number, retrieved October 2026).

Why SKUs matter for your store

SKUs matter because they are how your store actually counts and manages stock. Without them, a catalog of similar variants quickly becomes impossible to track accurately.

They keep inventory correct. When a sale reduces stock, the SKU tells the system exactly which variant to decrement, so your counts stay right across sizes and colors.

They also make a store work across channels. A single SKU can tie the same item together on your website, your marketplace listings, and your warehouse, so stock stays in sync from listing to shipping.

And they power your reporting. Sales by SKU show which specific variants sell, which sit dead, and what to reorder, turning a raw product list into a manageable catalog.

In our experience, the first thing to sort out when moving a catalog online is a consistent SKU scheme. Variants without their own codes turn into duplicate and mismatched listings that are painful to untangle later. Setting the pattern before the products go in saves that cleanup.

Frequently asked questions

Do I have to use SKUs on a small store?

Not strictly, but they help the moment you carry variants or grow. A small store or catalog with five simple products can manage without formal SKUs, though even then they make reporting cleaner. Once you have sizes, colors, or dozens of items, SKUs are what keep stock counts and orders accurate. Setting up a simple, consistent scheme early is far easier than retrofitting one across a live catalog later.

What is the difference between an SKU and a barcode?

An SKU is your own internal tracking code, while a barcode usually encodes a universal UPC assigned through GS1. You create and control your SKUs; you cannot invent a valid UPC. A product can carry both: the manufacturer's barcode for universal scanning, and your SKU for your own inventory and reporting. Many small sellers who do not need retail barcodes use SKUs alone.

Can two products share the same SKU?

No, and they should not. Each SKU must map to exactly one specific product variant, because that is the whole point of the code. Reusing a SKU across two items, or recycling an old one for a new product, corrupts your stock counts and your sales history. If you run out of a product permanently, retire its SKU rather than reassign it to something else.

How do I create SKUs for my products?

Design a short, consistent pattern, then apply it across the whole catalog. Use meaningful segments, such as product type, then a key attribute, then the variant, separated by hyphens. Put the most important detail first so the codes sort logically. Keep them uppercase, avoid spaces and odd characters, and document the scheme so anyone on your team can read and extend it.

Do SKUs affect SEO?

No, SKUs are internal and do not directly influence search rankings. They live in your inventory system, not in the content search engines read to rank you. What matters for search is your product page's title, description, and structured data, not the SKU code behind it. That said, a tidy SKU system keeps your product pages and stock accurate, which supports the buyer experience search ultimately rewards.

Getting your catalog structured right

Storming Solutions builds business websites for Malaysian businesses from Kuala Lumpur, and we set up your product catalog so stock, variants, and reporting hold together from day one. We help you design a clean SKU scheme, wire it into your store and inventory, and keep it consistent as your range grows.

Moving a product range online and unsure how to organize it? Talk to us about your catalog, and see how our web development turns a messy product list into a store you can actually manage, from category to product page.