SKU, barcode, UPC and GTIN: how they differ

They're not the same thing. A SKU is a code. A barcode is a picture of a code that a scanner can read. A GTIN is a standard number. A UPC is one kind of GTIN.

The four terms in one line each

• SKU. Your own code for one item type. It can be anything you decide, because these identifiers are not regulated or standardised.¹
• Barcode. A way of showing data in a visual form a machine can read.² A SKU is sometimes represented via a barcode.¹
• GTIN. A Global Trade Item Number. These identifiers are used to look up product information in a database, often by scanning a barcode on the product.³
• UPC. A 12-digit number assigned to each trade item. Technically it's a UPC-A.⁴

How the GTIN family is arranged

• Lengths. GTINs may be eight, 12, 13 or 14 digits long.³
• Special cases. The UPC, the European Article Number (EAN) and the Australian Product Number (APN) are special cases of GTINs.¹
• One per trade item type. Each type of trade item is given its own GTIN.³
• Who assigns them. The GS1 organisation hands out the digits behind UPC and EAN barcodes.⁴ A small business can read how to get its own in where product barcode numbers come from.

Side by side

Do you need both a SKU and a barcode?

Usually you want a SKU for every item. A barcode is optional, until a scanner or a seller asks for one.

• Selling only your own made items, in your own shop. A SKU is the part you need. You can print it as a barcode so staff scan instead of typing. A code you invent is fine here, because SKUs aren't standardised.¹
• Reselling other makers' goods. Their barcodes may already be on the packs. You can keep the maker's SKU or create your own.¹
• Selling through a large retailer or marketplace. Check what that seller asks for. Some retailers, such as clothing and furniture sellers, don't use the GS1 system and use other codes instead.⁴

Mistakes to avoid

• Treating a SKU as a GTIN. A made-up code isn't a global number. It won't match a product database somewhere else.
• Printing someone else's GTIN on your own product. The number belongs to whoever licensed it. See the sourcing page linked above.
• Giving two item types one barcode. Each type of trade item is given its own GTIN, so a different size or colour normally needs a different one.³

Next, common barcode types shows what the lines and squares themselves can look like.