Barcodes for Products You Sell: What You Need to Know

Published 9 October 2026

If you're about to sell a product through shops or big online marketplaces, you'll be asked for a barcode. The tricky part isn't drawing the barcode. It's getting the right number. Here's how it works.

Barcode image vs barcode number

A barcode has two parts. There's the number, which identifies your product, and there's the picture of bars that a scanner reads. This site makes the picture. It doesn't issue, register or check product numbers.

That matters because retailers and marketplaces want the number to be genuine, meaning it was issued to your business, and not one you made up.

What are GTIN, UPC and EAN?

• GTIN (Global Trade Item Number) is the name for the number itself.
• UPC is the 12-digit GTIN used traditionally in North America.
• EAN is the 13-digit GTIN used in most other parts of the world.

Not sure which you need? Read EAN-13 vs UPC-A.

Where do the numbers come from?

Product numbers are issued through GS1, the standards organisation that manages them, via its local member organisation in each country. When you join, you get a company prefix, and you create product numbers from it. This keeps every number unique in the world, so two different products never share one.

You may see sites that sell cheap, resold numbers. Some retailers and marketplaces check numbers against GS1's records and may reject products using numbers that aren't registered to you. Read the rules of the places you want to sell on before you buy numbers from anyone.

When you don't need GS1

• Stock control inside your own business, where nobody outside ever scans the barcode
• Labels for your own shelves, boxes or tools
• Testing a till or inventory system
• Training, mock-ups and packaging designs

For those, any correctly formed number works, and a flexible format like Code 128 lets you use letters and your own codes.

A simple path for a small seller

1. Check what your retailer or marketplace requires, and whether they want GS1-issued numbers.
2. If they do, contact your country's GS1 office and get your company prefix.
3. Create a product number for each item (and each variant, such as size or colour, if it's sold separately).
4. Make the barcode image here with the EAN-13 generator or the UPC-A generator.
5. Print a test label and scan it before you print your packaging. See how to print barcode labels that scan.

Cartons and cases

If you ship cartons to distributors, they may ask for a 14-digit GTIN-14 barcode on the outer box. That's the ITF-14 format.

Requirements differ between countries and platforms, so treat this as a general guide and check with GS1 or your retailer for the rules that apply to you.

Common questions from new sellers

Do I need a different barcode for every variation?

Usually yes. A red t-shirt in size M and a blue one in size L are different products, so they each get their own number. A pack of six is also a different product from a single item.

Can I make up a number?

For your own internal use, yes. For selling through shops or big marketplaces, no, because numbers have to be unique worldwide. A made-up number could clash with a real product that already uses it.

What about books?

Books use ISBNs, which come from your country's ISBN agency. An ISBN-13 is printed as an EAN-13, so you can use the same generator.

What if my product is tiny?

Look at EAN-8 or UPC-E, but check with your GS1 office first. They normally only allow short barcodes where a full one truly won't fit.

Where does this site fit in?

Think of it as the printing step. You bring the number, we make a clean barcode image that scans, with the check digit worked out. Then you can print the labels and test them.

Frequently asked questions

More guides

• Code 128 vs Code 39: Which One Should You Use?
• How Barcode Check Digits Work (With a Worked Example)
• QR Code Size and Error Correction Explained

See all guides