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Key takeaways
- A UPC is just the 12-digit kind of GTIN, and an EAN is the 13-digit kind. Skip the jargon and put the number from your packaging in Shopify's Barcode field.
- Only enter barcodes your products really have. Google says items you make yourself or sell under your own label usually don't need one.
- Since September 2026 a Shopify variant can hold up to 20 barcodes, but sales channel feeds still read the first one.
- Set a product category on every product. It comes from Shopify's standard list and adds attributes such as color and material, while type and tags are your own words.
What a GTIN is
A Global Trade Item Number (GTIN) identifies one product anywhere in the world. GS1, the standards body behind barcodes, calls it "the number found under a product barcode's black and white lines." The barcode is the picture of that number that a scanner reads.
The other names are mostly lengths. A 12-digit GTIN is a UPC, used mostly in North America, and a 13-digit GTIN is an EAN, used in most other places. Very small items get 8 digits, and cases of goods get 14, per the Wikipedia summary of the GS1 standard.
| Format | Digits | Also called | Typical use |
|---|---|---|---|
| GTIN-12 | 12 | UPC | Retail products, mostly in North America |
| GTIN-13 | 13 | EAN, JAN; ISBN-13 for books | Retail products in most other countries |
| GTIN-8 | 8 | EAN-8 | Very small items |
| GTIN-14 | 14 | ITF-14 | Cases and multipacks |
A GTIN is not a SKU. A SKU is your own stock code, and Shopify's help center says "SKUs are different from barcodes", with a field for each. A waxed canvas bag shop might use WX-WKND-OLV as the SKU for its olive weekender, while the tag carries a 12-digit UPC.
The last digit is a check digit worked out from the others, so you can't make one up. Google's Merchant Center, the tool where stores send product data to Google Shopping, asks for a check digit that is valid under the GS1 standard. It also turns away restricted prefixes. Those are codes that start with 2, 02 or 04, plus coupon codes that start with 05, 98 or 99.
Where barcodes go in Shopify
In Shopify, each variant has its own barcode. That matters because a bag in olive and the same bag in navy are different items to a scanner, and Google asks for a separate GTIN for each variant.
Shopify changed this field on September 8, 2026. A variant can now hold up to 20 barcodes, and each one is checked against its format as you type, according to the Shopify changelog. You add them on the variant's details page.
You can also use the bulk editor for many products at once, and a product CSV file has a Variant Barcodes column for the same job. One detail is easy to miss. Anything that expects one barcode, such as a sales channel feed, still reads only the first, so put the real GTIN first.
Shopify's guide to optimizing products for AI platforms lists the barcode among the fields that AI platforms consider. The title and description are on the same list.
OpenAI's own feed format treats the GTIN with the same care. It wants a GTIN in one of the four standard lengths with a valid check digit. It also says to leave the field out if no GTIN was assigned. Shopify Catalog sends your data to ChatGPT for you, but the spec shows what a clean barcode looks like to an AI channel.
When you can skip a GTIN
Many Shopify products have no GTIN at all, and that's fine. Google says store brands and private label goods generally don't need one. Custom or one-of-a-kind items can leave the field blank too. Google's examples include handmade goods and art.
For those products, Google has a setting called identifier_exists. Set to "no", it tells Google that no product identifier exists. Google's own examples are a custom black dress and a hand-knitted wool scarf. Use it only when you are sure, because Google warns about products marked "no" that show signs of having an identifier.
The reverse mistake costs more. Google says that if a product does have a GTIN and you leave it out, the listing could be disapproved. So a reseller who carries other brands should copy each maker's GTIN into Shopify. A maker of handmade goods shouldn't buy codes just to fill the box.
That second group often feels stuck. In 2023 one handmade seller wrote in Shopify's forum, "everything on my store is handmade by me no one else. How do I get my products seen". That is one merchant's report, and Google's answer for that store is the identifier setting above.
You may also see the phrase "GTIN exemption". When we checked Google results for it in October 2026, most top results were about Amazon's own process. For Google Shopping and AI channels fed by Shopify, there is nothing to apply for. You leave the barcode blank and describe the product well.
Product category, product type and tags
A barcode says which exact item this is. A category says what kind of item it is. Shopify gives you three places to describe that, and they do different jobs.
The product category comes from Shopify's Standard Product Taxonomy, a shared list of categories that runs from broad groups down to very specific kinds of product. In 2024 Shopify said it mapped over 10,000 product categories with over 1,000 attributes, and it publishes the list openly on GitHub. Each product gets one category. When you create a product, Shopify can suggest a category based on its name and description, and on its images.
Picking a category adds category metafields, which the taxonomy calls attributes. They are ready-made fields for details such as color or fabric. Shopify's page on product categories says the category also sets the tax rate with Shopify Tax and helps channels such as Google that expect standard categories. A product with no category is saved as uncategorized.
Product type is different. It is a label you write yourself, such as "Weekender bag", for groupings Shopify's list doesn't have. Shopify allows one type per product and recommends standard categories where one fits.
Tags are short labels for organizing. Shopify allows up to 250 per product and uses them for automated collections and some theme filters. Its help page on tags also says search engines don't use them, so they won't help you rank.
| Field | Where values come from | How many | What it does | Bag shop example |
|---|---|---|---|---|
| Product category | Shopify's standard list | One | Tax, channel mapping, attributes such as color | The closest bag category on the list |
| Product type | Your own words | One | Your own grouping and filtering | Weekender bag |
| Tags | Your own words | Up to 250 | Collections, filters, internal sorting | waxed-canvas, travel, olive |
Category metafields are where merchants struggle most. One wrote in 2024, "I have big struggles trying to figure out the 'New' Category Metafields feature." Another, with a large catalog, warned that with many product types the admin "soon becomes messy." Those are individual reports, but they explain why so many stores leave the category blank.
Why AI shopping channels read these fields
When a shopper asks ChatGPT for a waxed canvas weekender under $200, ChatGPT has to decide which products fit. OpenAI says it relies on structured metadata from data providers to do that, meaning structured product fields. For a Shopify store, that provider is Shopify Catalog, which shares your product data with AI channels in a structured form. Our guide to how AI search works for online stores covers the bigger picture.
The fields in this article are the structured part. The category and its attributes say what the item is and what it's made of. The barcode helps a channel match your listing to the exact item a shopper wants, which is how Google describes its use of GTINs. When several stores sell one item, OpenAI says ChatGPT then ranks the stores on factors such as stock and price. That only works once it knows the listings are the same item.
Shopify's own pages point the same way. Its Shopify Catalog page tells merchants to keep categories, variants and options accurate and complete. Its Catalog rules also leave out products with no category at all, per the requirements page. If your details live in metafields instead, Shopify Catalog mapping lets you choose which sources it reads.
None of this decides who wins a recommendation. Shopify says each AI platform has its own factors. But a product with no category and no barcode gives an assistant very little to work with. If you sell through ChatGPT, our guide to selling through ChatGPT on Shopify covers the other rules.
Fix them in Shopify admin, step by step
Start with your best sellers, since they matter most. To see which products are missing these fields, run our free product data checker on up to 20 products first.
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Open the product and pick a category
In your Shopify admin, open Products. Then open the product you want to fix. Search for a category in the Category section, or click down through the levels. Choose the most specific one that fits. Shopify's AI suggestion is a starting point. Check it before you save.
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Fill in the category attributes
Under the category, add the attributes that apply to your item. Color and material are common ones. If you link color entries to your variant options, themes that support it can show color swatches.
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Set the product type and vendor
Under Product organization, type a product type in plain words a shopper would use. Fill in the vendor with your brand name, or the maker's brand if you resell.
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Add real barcodes to each variant
Open each variant and add its GTIN in the barcode field, with the real GTIN first. Copy it from the packaging or from the maker. If the item has none, leave it blank. Never invent one.
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Tidy your tags and option names
Keep tags short and consistent, such as waxed-canvas rather than Waxed Canvas!!. Rename options called "Title" or "Option1" to the choice a shopper makes, such as Size.
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Do the rest in bulk
Select many products and click Bulk edit. Then add the Product category column and any others you need. For a large catalog, export a CSV file. Fill in the columns, then import it again.
Then check the result where AI channels see it. Shopify's Agentic page gives each product a listing quality score, and our guide to checking your store's AI visibility for free shows what to watch over the next month.
How ShopAEO helps
ShopAEO does this work across your catalog, and you approve every change.
- It picks each product's category from Shopify's standard list. Unclear matches wait for you to choose.
- It fills in a missing product type and adds up to 5 tags, using only words already in your product data.
- It renames generic options like "Title" or "Option1" when the values make the right name clear.
- It saves the UPC or EAN barcodes you enter after checking each one is valid, and it never invents one.
To see which of these gaps your products have, run the free product data checker, or read everything ShopAEO writes.
Sources
- What is the difference between a GS1 GTIN, a barcode, an EAN and a UPC?, GS1 Support (accessed October 19, 2026).
- Global Trade Item Number, Wikipedia (accessed October 19, 2026).
- GTIN [gtin], Google Merchant Center Help (accessed October 19, 2026).
- Identifier exists [identifier_exists], Google Merchant Center Help (accessed October 19, 2026).
- Multiple barcodes in variants, Shopify changelog (September 8, 2026).
- SKUs and barcodes, Shopify Help Center (accessed October 19, 2026).
- Product category, Shopify Help Center (accessed October 19, 2026).
- Product type, Shopify Help Center (accessed October 19, 2026).
- Tags, Shopify Help Center (accessed October 19, 2026).
- Shopify's new product taxonomy, Shopify blog, Agatha Krajewski (June 24, 2024).
- Shopify Standard Product Taxonomy, Shopify on GitHub (accessed October 19, 2026).
- Optimizing your products for AI platforms, Shopify Help Center (accessed October 19, 2026).
- Shopify Catalog, Shopify Help Center (accessed October 19, 2026).
- Customizing your product data for Shopify Catalog, Shopify Help Center (accessed October 19, 2026).
- Shopify Catalog requirements, Shopify Help Center (accessed October 19, 2026).
- Products feed reference, OpenAI Commerce documentation (stable version, accessed October 19, 2026).
- Shopping with ChatGPT Search, OpenAI Help Center (accessed October 19, 2026).
- Problem with 'you need to add a GTIN or MPN', Shopify Community forum (February 4, 2023). Merchant report, not a Shopify statement.
- Product Category Metafields, Shopify Community forum (June to September 2024). Merchant reports, not a Shopify statement.
Frequently asked questions
Is a GTIN the same as a UPC?
A UPC is one kind of GTIN. GS1 says a GTIN-12 is also called a UPC and is used mostly in North America, while a GTIN-13 is also called an EAN. So every UPC is a GTIN, but not every GTIN is a UPC.
Is a GTIN the same as a SKU?
No. A GTIN identifies a product anywhere in the world and is issued by GS1. A SKU is your own internal code for tracking stock. Shopify keeps them in separate fields, and you can fill in both.
How do I get a GTIN for my product?
GTINs are issued by GS1, so the place to start is the GS1 organization in your country. If you resell another brand's products, the GTIN is already on the packaging, and you only need to copy it into Shopify.
Is a GTIN mandatory?
Not for every product. Google recommends a GTIN for products that have one from their maker. It says store brands usually don't need one. The same goes for custom and handmade items. If a product does have a GTIN and you leave it out, Google warns it could be disapproved.
What is the difference between product category and product type in Shopify?
Product category is picked from Shopify's Standard Product Taxonomy, a shared list of categories. It affects the tax rate and which attributes you can add. Product type is a free text label you make up, such as Weekender bag. Each product has one of each.
Do Shopify product tags help SEO?
Not directly. Shopify says search engines don't use tags. Tags help you organize products and build automated collections. Some themes also use them as filters. Shopify's guidance on AI platforms does list tags among the fields they consider.
