EAN, UPC, ISBN and ASIN: how each product code differs

If you sell on Amazon Mexico and MercadoLibre and keep confusing EAN, UPC, ISBN and ASIN, here is the short answer: EAN and UPC are two formats of the same global barcode standard, which today is grouped under the name GTIN (that’s why the keyword “ean gtin” blurs the two together). The EAN is the 13-digit code that dominates in Mexico, Europe and most of the world; the UPC is its 12-digit cousin that was born in the United States. The ISBN is a specialized GTIN used only for books. And the ASIN is different from all of them: it is not a barcode you buy, but an internal identifier that Amazon assigns to every product inside its own catalog.

Put another way: EAN, UPC and ISBN live on the physical packaging of the product and serve to identify it in any store on the planet. The ASIN lives inside Amazon and only makes sense there. When you list on Amazon, you provide a GTIN (usually an EAN or UPC) and Amazon returns an ASIN that links your offer to the correct listing. Mixing up these roles is one of the most common causes of blocked listings, duplicate listings, and stock that never reconciles across channels.

In this guide we separate each code, tell you which one you need depending on what and where you sell, and explain why keeping all this information scattered across several dashboards and Excel sheets is exactly the problem that a real-time catalog solves.

gtin: the umbrella that covers ean and upc

Before comparing codes, you need to understand the term that unites them. GTIN stands for Global Trade Item Number, and it is the modern name that GS1 (the body that administers these standards) gave to the whole family of product identifiers. When an Amazon or MercadoLibre form asks you for a “GTIN,” it accepts any of its variants: GTIN-13 (which is the good old EAN), GTIN-12 (the UPC), GTIN-8 (the short version for small packaging) and GTIN-14 (for cases and logistics groupings).

This is why the “ean gtin” search makes so much sense: many people see the “GTIN” field on the marketplace, have an EAN code printed on their product, and don’t know whether they’re the same thing. They are. Your 13-digit EAN is a GTIN. You don’t have to convert anything or request a new code. The system simply uses the technical umbrella name, while on the product box you’ll see “EAN” printed.

The practical takeaway for the multichannel seller is clear: a single GTIN should be the backbone that identifies your product across all your channels. That code doesn’t change whether you sell on Amazon, on Meli, on your Shopify, or ship it to a 3PL. It is the anchor point that lets stock drop everywhere when you sell a unit on one channel. When that anchor is lost or captured incorrectly, the inventory chaos begins and you’re forced to reconcile by hand.

ean: 13 digits, the standard in mexico and the world

The EAN (European Article Number, now officially called International Article Number) is the 13-digit barcode you see on most products you buy in Mexico. It’s made up of a country or region prefix assigned by GS1, the company number, the item number, and a final check digit calculated mathematically from the other twelve.

That check digit matters because it’s the first thing a marketplace validates. If you mistype a number or drop a digit, the check digit no longer matches and the listing is rejected before it’s even created. It’s a silent and very common error when codes are captured by hand from a spreadsheet. We cover this kind of failure in depth in the guide on EAN and GTIN errors that block your listings.

For the Mexican seller, the EAN is almost always your starting point. Prefixes assigned to Mexican companies usually start with 750, but that doesn’t limit where you sell: an EAN is global. The same 13-digit code works to list on Amazon Mexico, on MercadoLibre, and to register the product in your Shopify. The advantage of working with EAN as your main identifier is that it’s already the longest, most universal format; embedding a 12-digit UPC inside an EAN is as simple as prefixing it with a zero.

upc: 12 digits, the u.s. variant

The UPC (Universal Product Code) is the 12-digit barcode that was born in the United States in the 1970s and is still dominant in the North American market. Structurally it’s a younger sibling of the EAN: one digit shorter, the same logic of company number, item number, and check digit. In fact, a UPC is nothing more than an EAN missing its first digit.

As a Mexican seller you’ll run into UPC mainly in two scenarios. The first is when you resell products imported from the United States that already carry their UPC printed: that code is perfectly valid for listing on Amazon Mexico, you don’t need to convert it. The second is when you sell, or plan to sell, on Amazon US, where the UPC is still the standard currency even though the EAN is also accepted.

The good news is that EAN and UPC are interchangeable at the identification level. Amazon and MercadoLibre recognize both under the GTIN field. The problem isn’t which format you use, but consistency: if you saved the 12-digit UPC in Shopify, the 13-digit EAN in Amazon, and a hyphenated version in your Excel, your system has three representations of the same product and none of them automatically matches the others. That fragmentation is exactly what a unified catalog solves: it normalizes the code once and propagates it clean to every channel.

EAN / GTIN: the same global product-identification standard under two names. Your 13-digit EAN is already a valid GTIN, you don’t need to convert it to list on a marketplace.

isbn: the specialized gtin for books

The ISBN (International Standard Book Number) is a special case within the GTIN family. It’s a 13-digit identifier (before 2007 it was 10 digits) reserved exclusively for books and editorial publications. And here comes the detail that confuses many people: the modern ISBN is a GTIN. The 13-digit ISBNs start with the prefix 978 or 979, which GS1 assigned specifically to the publishing world. That prefix is known as “Bookland.”

This means that if you sell books, your ISBN works as the GTIN that Amazon or MercadoLibre asks for. You don’t need an additional EAN: the barcode on the back cover of any book is, technically, both an ISBN and an EAN-13. A single number fulfills both roles.

For a seller handling mixed categories, the lesson is not to treat books as a weird case that breaks your flow. A good catalog system understands that the ISBN goes in the same GTIN field as any other product and validates it the same way, calculating its check digit and detecting duplicates. If you sell mostly electronics or consumables, you’ll probably never touch an ISBN; but if your catalog includes books, editorial stationery, or educational material, it pays to have a tool that recognizes them without friction instead of forcing you into a separate process.

asin: the identifier that only exists inside amazon

Here is the most important difference in this whole guide. The ASIN (Amazon Standard Identification Number) is not a barcode and you don’t buy it. It’s a 10-character alphanumeric identifier that Amazon generates and assigns internally to every product in its catalog. It doesn’t live on the physical packaging, it isn’t managed by GS1, and it’s useless outside Amazon.

The flow works like this: when you create a listing on Amazon, you provide a GTIN (your EAN or UPC). Amazon looks up that GTIN in its catalog. If a product with that code already exists, your offer is linked to the ASIN that was already created and you share that product page with other sellers. If it doesn’t exist, Amazon creates a new ASIN from your information. That’s why a single physical product has one universal GTIN but can have different ASINs in each Amazon marketplace (one on Amazon Mexico, another on Amazon US, another on Amazon Spain).

This distinction causes the most headaches for the multichannel seller. The GTIN is your universal key; the ASIN is Amazon-local. MercadoLibre doesn’t use ASIN, it uses its own listing ID (the MLM). Shopify doesn’t require either. So a single product ends up existing with a GTIN, one ASIN per Amazon marketplace, one MLM per Meli listing, and your own internal SKU. Keeping all those identifiers linked by hand, in an Excel sheet, is where traceability breaks down and where stock stops reconciling.

why stitching these codes by hand costs you sales

Once you’ve separated the four codes, the real problem shows up when you try to operate with them across several channels at once. Each platform shows you its own version of the truth: Amazon speaks to you in ASIN, MercadoLibre in MLM, your Shopify in SKU, and your supplier in EAN. None of those dashboards knows about the others. When you sell a unit on one channel, that channel drops its own counter, but the rest still think you have the unit available.

You know the result: overselling, cancellations that hurt your reputation, listings blocked because the same product ended up duplicated under two different ASINs, and hours lost copying numbers from a dashboard into a spreadsheet trying to reconcile. Every time you capture a GTIN by hand there’s a risk of a mistyped digit that breaks the check digit. Every time one channel sells and another doesn’t hear about it, your true availability stops being reliable.

Unified catalog: a single master record per product that holds its GTIN, its ASINs per marketplace, its MLM, and your SKU, and feeds every channel consistent data from there.

The solution isn’t more spreadsheet discipline, it’s a unified catalog that uses the GTIN as its backbone. With iqseller each product lives as a master record: its EAN/UPC validated once, automatically linked to its ASIN on each Amazon, to its MercadoLibre listing, and to your Shopify or 3PL SKU. When a unit sells on any channel, real-time inventory deducts the stock everywhere instantly, without you touching a spreadsheet.

True availability: the units you can actually sell right now, after subtracting what’s committed across all your channels, not the number each dashboard shows on its own.

Understanding the difference between EAN, UPC, ISBN and ASIN is the first step; the second is stopping the habit of managing them separately. EAN and UPC are your universal GTIN, the ISBN is that same GTIN for books, and the ASIN is Amazon’s internal link derived from your GTIN. When that hierarchy lives in one place and syncs itself, you stop chasing numbers and go back to selling with the certainty that your stock adds up.