How to Locate Amazon Product Identifiers: ASIN, GTIN, UPC, EAN, and ISBN

Most sellers treat product identifiers as paperwork - a box to fill on a listing form. That’s the mistake. On Amazon, the identifier you pick determines whether your listing goes live, gets suppressed, or triggers an account audit. Get the ASIN-to-GTIN relationship wrong and you’re not fixing copy; you’re opening a Seller Support case.

This page shows you where each identifier lives, what Amazon now verifies against GS1, the March 31, 2026 FBA barcode change that flips the playbook for brand owners and resellers, and the error codes to expect when something is off.

Table of Contents

1. Product Identifiers on Amazon: The Short Version
2. Finding the ASIN
3. Finding the GTIN (UPC, EAN, ISBN, JAN, GTIN-14)
4. Where to Obtain a GTIN - and What It Costs
5. The March 31, 2026 FBA Barcode Change
6. GTIN Exemption vs. Buying GS1 Barcodes
7. Common GTIN Errors and How to Fix Them
8. Identifier Requirements on Walmart, eBay, Google, and Shopify
9. FAQ

Product Identifiers on Amazon: The Short Version

Every sellable unit on Amazon carries at least two numbers that matter: an ASIN (Amazon’s internal 10-character code, auto-assigned) and a GTIN (the industry-standard barcode - UPC, EAN, ISBN, JAN, or GTIN-14 - required to create most new listings and verified against the GS1 database).

Identifier	Format	Issued By	Role
ASIN	10 alphanumeric (e.g., B00ZV9PXP2)	Amazon	Internal catalog key
UPC	12 digits	GS1	Most common GTIN in North America
EAN	13 digits	GS1	European/international
ISBN	10 or 13 digits	ISBN agencies	Books
JAN	13 digits	GS1 Japan	Japan
GTIN-14	14 digits	GS1	Case packs / bulk packaging
FNSKU	10 characters	Amazon	FBA-specific - links inventory to a seller

ASIN, GTIN, and FNSKU aren’t interchangeable. The ASIN identifies the catalog page, the GTIN identifies the product in the industry, the FNSKU identifies your physical unit in an FBA warehouse.

Finding the ASIN

An ASIN is ten characters, letters and numbers, always unique on Amazon. You don’t buy it - Amazon generates one the first time a product is catalogued. Books are the exception: an ISBN doubles as the ASIN.

Where to look:

1. Product URL. On any Amazon product page, the ASIN sits after /dp/ - e.g., https://www.amazon.com/dp/B00ZV9PXP2 → ASIN B00ZV9PXP2.
2. Product detail page. “Product information” / “Product details” lists it explicitly.
3. Seller Central. In Manage Inventory and every listing, advertising, and bulk listing report.

Two things that aren’t obvious from the definition. Amazon’s variation and catalog enforcement has tightened hard in 2025-2026 - automated systems now flag and break parent-child structures that don’t meet policy, and in 2026 reviews no longer carry across variations that differ meaningfully in function. ASIN hygiene is no longer a back-office concern. And once an ASIN exists, you don’t create a new one for the same product - you list against the existing ASIN using its GTIN.

For parent-child rules and the 2026 review-sharing rollout, see Defining Amazon ASINs, Variation Relationships, and Parent-Child ASINs.

Finding the GTIN (UPC, EAN, ISBN, JAN, GTIN-14)

GTINs are the universal barcodes sitting underneath Amazon’s ASIN - what every retailer, not just Amazon, uses to identify a product across supply chains.

Where to find yours:

• On the packaging - the digits printed directly below or above the barcode.
• From the manufacturer - if you’re reselling someone else’s brand, the manufacturer’s GTIN is the one Amazon expects.
• From GS1 - if you’re the brand owner, you buy it directly from GS1 (or your country’s equivalent).
• From GEPIR - to verify a GTIN you already have, run it through gepir.gs1.org. If GEPIR doesn’t recognize it, Amazon won’t either.

Three rules sellers get wrong:

• Digits only - no dashes, no spaces.
• Select the correct Product ID Type in Seller Central. A 12-digit UPC goes in as “UPC,” not “GTIN.” The GTIN dropdown expects 14 digits.
• Every sellable unit needs its own GTIN. A single bottle, a 3-pack, and a gift bundle are three different products with three different codes. Case packs use GTIN-14s, separate from the consumer-unit GTIN.

Where to Obtain a GTIN - and What It Costs

Two legitimate sources exist: the brand’s manufacturer, or GS1. Amazon verifies every barcode against the GS1 global database and explicitly rejects third-party “resold” UPCs. Those resold codes pass a casual scanner and fail Amazon’s GS1 check.

Option	Cost (as of early 2026)	Best For
Single GTIN from GS1 US	$30 one-time	1-10 products
GS1 Company Prefix	$250+ annual license	Growing catalog
Manufacturer-provided	Free	Resellers of existing brands
Third-party “resold” UPC	$5-$10	Don’t. Amazon will reject it.

For books, the identifier is an ISBN issued by the U.S. ISBN Agency or your country’s equivalent.

Which to pick is simple math. A single $30 GTIN is cheaper upfront than a $250+ Company Prefix. But a Company Prefix gets you a block of GTINs under your own GS1-licensed prefix - which is what larger retailers and Amazon’s verification system prefer. Above roughly eight SKUs, the Company Prefix pays for itself within the first year.

The March 31, 2026 FBA Barcode Change

The largest change to how GTINs operate inside FBA in years, and it affects brand owners and resellers in opposite directions. Amazon is ending commingling (pooling identical units from different sellers under one manufacturer barcode); virtual tracking replaces the physical pooling. FBA Prep and Labeling Service already ended January 1, 2026 - sellers handle labeling independently.

Brand owners in Brand Registry (Brand Representative role): Ship using the manufacturer barcode (your GS1 UPC/EAN/ISBN) - no FNSKU stickers required. No more re-stickering costs; industry estimates put the total savings around $600M per year. To switch: Seller Central → Settings → Fulfillment by Amazon → FBA Product Barcode Preference → Manufacturer barcode. Verify your barcodes pass GS1 verification first.

Resellers (not the brand owner): FNSKUs become mandatory on every unit. Inventory arriving after March 31 without FNSKUs is classified as defective. Plan for labeling in-house, or pay a 3PL/prep service (typically $0.10-$0.55 per unit). New budget line that didn’t exist before.

The knock-on effect: if you’re a brand owner, your manufacturer barcode is now the primary tracking mechanism inside Amazon’s warehouses. A bad GTIN isn’t just a listing problem - it’s a fulfillment problem. Sellers who skated by with cheap third-party barcodes will hit a wall.

GTIN Exemption vs. Buying GS1 Barcodes

Amazon allows a GTIN exemption for products that legitimately don’t have a standard barcode - private label, handmade, certain unbranded generics. It’s not a loophole for non-compliant items.

The process in Seller Central: Inventory → Add a Product; enter the exact brand name (or “Generic” for unbranded) and check “This product does not have a Product ID.” Submit images, website, and brand documentation. Approval typically takes 48 hours to a few weeks. Brand Registry enrollment expedites it - Amazon already has your brand on file.

When to skip the exemption and buy GS1 barcodes instead:

Scenario	Recommendation
Private label, few products, Amazon-only	Exemption is fine as a start
Private label, 10+ SKUs planned	Buy a GS1 Company Prefix - cheaper per SKU
Multi-channel (Amazon + Walmart + retail)	GS1 GTINs are non-negotiable
Reselling an existing brand	Use the manufacturer’s GTIN
Handmade / one-of-a-kind	Exemption fits
Retail expansion on the roadmap	Buy GS1 barcodes early

One nuance: Brand Registry enrollment does not eliminate the GTIN requirement. It makes exemptions faster to approve and removes the Error 5665 brand-approval step, but the default for most categories is still “GTIN required.”

Common GTIN Errors and How to Fix Them

Start every troubleshooting cycle with a GEPIR lookup at gepir.gs1.org - if the barcode doesn’t resolve there, nothing downstream will work.

Error Code	What It Means	First Thing to Check
5461	GTIN-to-brand mismatch, or no brand permission	Brand name matches GS1 registration exactly (spelling, spacing, capitalization)
5665	Brand not approved on Amazon	Brand Registry enrollment, or the catalog authorization form linked in the error
8572	Product identifier mismatch with Amazon’s catalog	GTIN resolves in GEPIR and brand matches the existing ASIN
8541 / 8542	GTIN already in use (duplicate / “hijacking”)	Open a Seller Support case with your GS1 certificate and screenshots
Invalid product identifier	GTIN not in GS1 database, expired, or wrong check digit	GEPIR lookup - if it fails, the barcode is not legitimate
Listing suppressed	Automated GS1 audit flagged it	GS1 license current? Brand name still matches?

The most common surprise: sellers pick “GTIN” in the Product ID Type dropdown for a 12-digit UPC. Amazon expects 14 digits for the GTIN option and rejects the code. Select “UPC” instead.

For a broader listing-problem overview, see Suppressed Listings.

Identifier Requirements on Walmart, eBay, Google, and Shopify

A GS1-issued GTIN works across every major platform globally - no separate barcodes per marketplace. But enforcement differs, which matters when a GTIN that works on eBay fails on Amazon.

Platform	GTIN Required?	Verification	Exemption
Amazon	Yes, most categories	Strict GS1 database verification	Yes, via Seller Central
Walmart Marketplace	Yes, all items	Strict; invalid IDs removed	Yes (private label, handmade)
eBay	Most new branded items	Moderate; MPN often accepted as alternative	Not required for used/vintage/one-of-a-kind
Google Shopping	Yes for brand-name products	Cross-references GS1 data	identifier_exists=false for custom items
Shopify	Optional on storefront	None on storefront; required when syncing to channels	N/A - not a marketplace

Amazon is the strictest verifier, so a GTIN that clears Amazon clears everywhere else. Walmart’s WFS program has its own quirk - it requires a scannable 12-digit UPC or 14-digit GTIN on packaging; vendor SKUs, FNSKUs, and EANs aren’t accepted for WFS labeling.

For operations across channels, see Multi-Channel Fulfillment.

FAQ

Where do I find the ASIN for a product I don’t sell yet? Copy the 10-character code after /dp/ in the product’s Amazon URL. It also appears under “Product information” on the detail page.

Can I reuse the same GTIN for a single item and a multi-pack of it? No. Every distinct sellable unit - single, 2-pack, bundle - needs its own GTIN.

Is a cheap third-party UPC good enough to list on Amazon? No. Amazon verifies every barcode against the GS1 global database; resold codes fail and trigger rejection or suppression.

Do I still need a GTIN if I’m in Brand Registry? Yes in most categories. Brand Registry doesn’t waive the GTIN requirement - it just makes GTIN exemption requests faster to approve.

What changes for me after March 31, 2026? Brand owners in Brand Registry can ship with the manufacturer barcode and stop paying for FNSKU stickers. Resellers must FNSKU-label every unit, or inventory is classified as defective.

What’s the fastest way to verify a GTIN? gepir.gs1.org. If GEPIR doesn’t return a brand owner, the barcode isn’t registered with GS1 and Amazon will reject it.

---