The short answer
If you want to sell a product in most shops, supermarkets or large marketplaces, you need a GTIN (Global Trade Item Number) from GS1, the non-profit standards body that runs the retail barcode system. GS1 has a member organization in more than a hundred countries. You join the one where your business is based, receive numbers you can assign, and assign one to each product. Then you print each number as a barcode.
If the barcode is only for your own use, such as stock rooms, library books, event tickets or equipment tags, you do not need GS1 at all. You can encode any value you like in a Code 128 or QR code.
Rule of thumb: if a retailer or marketplace has to identify your product from the code, use a GS1 number. If only your own systems read it, you can make up the value.
Step 1: decide whether you need a GS1 number
| Where the barcode is used | Needs a GS1 GTIN? | Usual format |
|---|---|---|
| Retail shelf and checkout (supermarkets, pharmacies, bookshops) | Yes (books use an ISBN) | EAN-13 or UPC-A |
| Amazon, Walmart Marketplace, Google Shopping listings | Usually, unless the marketplace grants an exemption | EAN-13 or UPC-A |
| Outer cases a retailer orders as a unit (for example, a case of 12) | Yes, the case gets its own GTIN (usually a GTIN-14) | ITF-14 or GS1-128 |
| Pallets and mixed shipments (logistics units) | An SSCC, created from your GS1 prefix | GS1-128 |
| Books with an ISBN | An ISBN from your national ISBN agency instead | EAN-13 starting 978 or 979 |
| Your own stock, assets, tickets, bin locations | No | Code 128, Code 39 or QR |
| Links to a website, menu or manual | No | QR code |
Step 2: get your numbers from GS1
Go to the GS1 organization for your country (the global site at gs1.org lists them all). Most offer two routes:
- A company prefix. You receive a prefix that identifies your company, with capacity to create a set number of GTINs from it, for example 10, 100 or 1,000. There is usually a joining fee and an annual fee that scales with the size of the block or your revenue.
- Single GTINs. Some GS1 organizations, including GS1 US, sell individual numbers for a one-off fee. This suits a small brand with a handful of products. Check whether your retailers accept single GTINs before you buy, because a few large buyers ask for a full company prefix.
Prices vary widely between countries and change over time, so check the current fee table on your local GS1 site rather than relying on a figure you read elsewhere.
Step 3: what about cheap barcodes sold online?
You will find sites selling "UPC codes" for a few dollars each. These may be numbers from a company prefix originally licensed to another company. A correctly printed barcode may scan, but scanning does not establish who licensed its number. The problem is what happens after the scan:
- GS1's records, which some retailers and marketplaces check, may show the number as belonging to the original company, or show no product record for you at all.
- Amazon states that it verifies product barcodes against the GS1 database and may remove listings whose barcode does not match the brand.
- Some large retailers ask for proof, such as a GS1 certificate in your company name, before they list a product.
Resold numbers can work for small independent shops that simply add your code to their own checkout system. If you plan to grow into bigger retailers or marketplaces, it is usually cheaper to start with GS1 than to relabel everything later.
Step 4: assign a number to each product
Every item a shop could stock or sell separately needs its own GTIN. In practice that means a new number for each:
- size or weight (250 g and 500 g are different products),
- color, scent or flavor,
- pack count (a single, a 4-pack and a 12-pack each get one),
- bundle or gift set.
Keep a simple spreadsheet: GTIN, product name, variant, date assigned. Your GS1 organization may also provide an online tool to record this, and filling it in helps retailers and marketplaces confirm that the number belongs to you. Do not reuse a number for a different product later, because old stock and old databases may still point to it.
Step 5: work out the check digit
The last digit of every GTIN is a check digit, calculated from the others so that a scanner can detect a misread. If you bought single GTINs, GS1 gives you complete numbers. If you have a company prefix, you build each number yourself: the prefix, then your own item reference, then the check digit. If you only have the digits before it, our check digit calculator works it out, and the studio adds it automatically when you type one digit short.
Step 6: turn the number into a barcode
Pick the format that matches your number and market:
- 13-digit GTIN: print it as an EAN-13. This is the default almost everywhere outside North America.
- 12-digit GTIN: print it as a UPC-A. Common in the United States and Canada. Our UPC vs EAN guide explains when to use which.
- Very small packs: an EAN-8, which needs its own separate number from GS1.
- Outer cartons: an ITF-14 carrying the case's own GTIN-14. It is often built from the product GTIN with an indicator digit in front and a new check digit, but follow your GS1 organization's rules for numbering cases.
In the Barcode Pro studio you paste the number, choose the format, and watch the scan badge. It decodes the rendered image with a real barcode reader and only shows PASS when the result reads back as your number. Export an SVG for your designer or printer, or a PNG for a label template.
Step 7: size it correctly and test a print
Retail barcodes have minimum sizes and need blank margins (quiet zones) on both sides. An EAN-13 at its standard size is about 37 mm wide, including quiet zones, and 26 mm tall, and scanners are designed for 80% to 200% of that. Shrinking the height to fit a tight label is the most common reason a barcode fails at checkout. The barcode size guide has the numbers for each format.
Before a full print run, print one label on the real material, scan it with a phone app and, if you can, with a handheld retail scanner. Dark bars on a white or very light background are the safest choice for anything that goes through a checkout. A good scan is not the same as a formal print-quality check: for large retail orders, a verification report from GS1 or your printer grades the barcode against the specification.
A quick checklist
- Retail or marketplace? Join GS1 in your country. Internal only? Skip GS1.
- Assign one GTIN per variant and write it down.
- Confirm the check digit.
- Choose EAN-13 or UPC-A (or ITF-14 for cartons).
- Generate the barcode and confirm it scans.
- For EAN or UPC, print at 80% to 200% of the standard size, with clear margins.
- Test a real print before ordering a full print run.
Frequently asked questions
Can I make up my own barcode number?
For internal use, yes: warehouse bins, asset tags and tickets can use any value that Code 128 can encode. For products sold through most retailers and marketplaces, no. Retail barcodes carry a GTIN, and a GTIN needs to be licensed through GS1 (or, for books, issued as an ISBN) so that trading partners can match it to you. Some marketplaces grant exemptions for certain products.
Is a barcode generator enough to sell in shops?
A generator only draws the barcode. You still need a valid GTIN licensed from GS1, or an ISBN for a book. Once you have the number, any correct generator, including Barcode Pro, can turn it into a print-ready image.
Do I need a different barcode for each product?
Yes. Every variant that a shop stocks separately needs its own GTIN: each size, color, flavor and pack count. A 6-pack and a single bottle of the same drink get different numbers.
What is the difference between a UPC and a GTIN?
GTIN is the name of the number. UPC-A and EAN-13 are the barcode formats that carry it at the checkout. A 12-digit GTIN is usually printed as a UPC-A, a 13-digit GTIN as an EAN-13.