What Is a SKU Number? Meaning, Examples, and Import Checks

A SKU number is a business’s internal code for a particular product or variant. SKU stands for stock keeping unit. Despite the word “number,” the code can contain letters as well as digits. A small blue mug and a large blue mug need different SKUs when you stock and fulfill them separately.

The code identifies what the item is. It does not tell you how many units are available, prove that a supplier has stock, or replace the identifiers another sales channel requires.

Runner AI publishes this guide. The Runner example below describes inspected CSV-planning source and regression-test cases, not a completed live import or a rule shared by every import route.

A SKU number example

Suppose you sell a ceramic mug in two colors and two capacities. The following is an illustrative naming plan, not a required format or a real supplier catalog.

Ivory, 250 ml has example SKU MUG-IVO-250 and 12 units on hand.
Ivory, 350 ml has example SKU MUG-IVO-350 and eight units on hand.
Blue, 250 ml has example SKU MUG-BLU-250 and six units on hand.
Blue, 350 ml has example SKU MUG-BLU-350 and zero units on hand.

This catalog has four SKUs and 26 physical units. The zero-stock blue mug still has an identity; selling out does not turn it into a different product. Conversely, six identical ivory 250 ml mugs share one SKU rather than needing six new codes.

The parent name, “Clay mug,” groups the choices for shoppers. The SKU distinguishes the exact version for stock records and fulfillment. Our product variations examples cover deciding which choices deserve separate variants. Here, the task is assigning and preserving their codes.

Amazon’s SKU guide likewise distinguishes a seller’s internal stock code from product identifiers used across businesses. Two sellers can assign different SKUs to the same manufacturer’s item.

SKU vs. barcode, GTIN, and serial number

Before copying a code from packaging, identify which kind it is. Several identifiers can belong to the same item without being interchangeable.

SKU. The business’s internal code for a product or variant.
GTIN, including UPC identifiers. A standardized identifier for a trade item across the supply chain. Keep the legitimate identifier supplied for that item.
Barcode. A machine-readable representation of data. It can encode a standardized identifier or an internal code, depending on its use.
Serial number. An identifier for one physical unit. Two units of the same variant can share a SKU but have different serial numbers.
Supplier item or variant ID. A reference to a record in the supplier’s system. Preserve the mapping needed to order the intended supplier variant.

Orderful’s stock-keeping-unit guide explains these distinctions, including barcode representation and individual-unit serial numbers. Do not assume that the digits beneath a barcode are your store’s SKU.

A SKU also does not become a valid GTIN because you enter it in a GTIN field. Keep internal and standardized identifiers in their intended fields. The broader ecommerce product data guide covers their place in the complete product record.

Create codes your team can keep using

There is no single universal SKU format. Choose a convention that fits the systems receiving your data, then document it before creating hundreds of codes.

Identify the stocked item. Decide which combination of product, size, color, or capacity the code represents. Do not assign a code to a combination you cannot supply.
Choose a consistent structure. A short product-family prefix followed by distinguishing attributes can work for a small catalog. A stable sequential code can also work when staff use a lookup rather than decoding attributes.
Check receiving-system limits. Confirm permitted characters, length, case handling, and uniqueness requirements in the actual store, warehouse, and channel tools.
Keep changing facts out of the identity. A price or shelf location can change while the item stays the same. Putting either into a SKU creates unnecessary renaming work.
Retain mappings and history. Keep supplier and channel identifiers alongside your own code. Do not reuse a retired code for an unrelated item.

Avasam’s SKU explanation describes both readable attribute-based codes and numeric approaches. The useful choice is the one your operation can maintain, not the one that packs the most information into a label.

Treat identifier columns as text when working in a spreadsheet. If your code begins with zeros, confirm that export and reimport preserve them. Changing only capitalization is also a poor way to distinguish two items because some systems compare codes without regard to case.

What a Runner import-planning check illustrates

Runner’s parseProductImportCsv function, in parse-product-import-csv.ts, reads Variant SKU as required text for its CSV-planning path. It compares lowercase versions of the supplied codes across the file and rejects a duplicate with DUPLICATE_SKU.

The companion regression test supplies BAG-S in one row and bag-s in another product’s row. It expects that duplicate-code rejection. A separate mapping case checks that the variant retains BAG-S as its SKU while keeping its barcode in a separate field.

That example supports two preparation checks: do not rely on letter case to make codes unique, and do not combine SKU and barcode data into one column. It does not establish global duplicate detection across existing store records or prove that an import reached a live catalog.

Use Runner’s Import products guide for the documented Store Operations workflow and its current template. That workflow documents Variant SKU as optional; the planning-path requirement above must not be treated as a universal import requirement.

Check identity after an import

Before submitting a file, write the expected result for a small, representative sample. For the mug example, expect four distinct variant codes with the intended color and capacity attached to each.

Then compare the resulting records with that sample:

Does each SKU still identify the same variant?
Are leading zeros, separators, and other significant characters preserved?
Did repeated rows create an unexpected duplicate?
Are barcode and supplier mappings still in their separate fields?
Are prices and quantities correct independently of the codes?

These are suggested acceptance checks, not results observed for this article. An accepted file or completed task is not a substitute for inspecting the resulting product records.

For stock setup, use Runner’s inventory and variants guide. If you are evaluating the product rather than preparing data, see the inventory-management feature overview. Assigning SKUs alone does not synchronize stock between systems.

Where can I find a SKU number?

Check the seller’s product or variant record, inventory export, item label, or order details when the seller exposes it there. Not every product page displays the internal SKU. If you only have a package barcode, ask the seller which identifier it represents rather than assuming it is the SKU.

Is a SKU the same as a part number?

Not necessarily. A manufacturer’s part number identifies an item in the manufacturer’s scheme. Your business can assign a separate internal SKU and retain the part number as another field. Match both to the exact variant before ordering a replacement.

Can two products have the same SKU?

Different businesses can use the same code independently. Within the inventory system where you use a SKU to distinguish items, assigning it to two different variants makes that reference ambiguous. Follow that system’s uniqueness rules and check for duplicates before import.

Do I need to buy SKU numbers?

You can define your own internal SKU convention. That is different from obtaining standardized product identifiers or meeting a marketplace’s listing requirements. A self-created stock code does not remove those separate obligations.