Product EAN Code: Management and Optimization Guide for eCommerce

EAN vs GTIN vs UPC/ISBN/MPN: What Your Catalog Needs (and When It's Mandatory)

The EAN code is the most common physical identifier in European retail and forms the technical basis for most catalog quality rules in a digital environment. However, terminological confusion between EAN, GTIN, UPC, and MPN is the root cause of thousands of synchronization errors in data feeds.

In this section, we clarify the technical hierarchy, critical differences with other identifiers, and why channels like Google Merchant Center demand absolute precision to avoid product suspensions.

What is GTIN, EAN, UPC, ISBN, and MPN

To avoid mapping errors and ownership conflicts between sales channels, it is vital to distinguish between the standard, the format, and the manufacturer reference.

GTIN (Global Trade Item Number) is the umbrella term for global product identifiers standardized by the GS1 organization. It is the abstract concept that encompasses the physical formats we see in barcodes:

• EAN (European Article Number): The standard format in Europe and most of the world. Technically, it usually corresponds to a GTIN-13.
• UPC (Universal Product Code): The predominant standard in North America. It corresponds to a GTIN-12.
• ISBN: Specific identifier for books. It follows its own rules for editions and formats, but in the feed, it maps to its own field or is converted to GTIN-13 (starting with 978).

On the other hand, the MPN (Manufacturer Part Number) is the internal reference assigned by the manufacturer. Unlike the GTIN, the MPN does not guarantee global uniqueness (two different manufacturers could use the reference "A-100").

How to approach it in your catalog: Always validate the length and the checksum (check digit) before accepting a code into your database. A headphone set with a 13-digit code is an EAN (GTIN-13). A book must map to the isbn field in the feed. Never use the MPN in the GTIN field; this is a critical error that confuses product matching algorithms on marketplaces.

Source: Official information on standards at GS1.

Why Google Merchant Center Requests GTIN and When It's Mandatory

Google uses the GTIN to group offers for the same product sold by different retailers. Knowing their exact policy prevents mass rejections and the loss of impressions in Shopping.

Google makes GTIN mandatory when the product has a manufacturer-assigned GTIN and the feed provides the brand. If the product is a craft, custom-made, or an antique without a code, Google allows omitting it using the identifier_exists attribute (which we will cover later), but requires proof.

Impact Example: A recognized brand smartphone (e.g., Samsung Galaxy) listed without its GTIN will be immediately flagged as "Insufficient product information" and will lose eligibility to appear in Shopping ads, regardless of your bid.

Typical Error: Uploading feeds that include the brand and the mpn, but leave the gtin field empty when the product actually exists in the GS1 catalog. This triggers a "Missing GTIN" alert.

Source: Official policy on identifiers in Google Merchant Center.

Where to Store Identifiers in Your Data Model and Why

To reduce discrepancies between your e-commerce and marketing channels, you need a master field (Source of Truth) at the variant level, not the parent product level.

Storage Strategy:

1. In a PIM (Product Information Management): Store a specific gtin field for each variant. The PIM acts as a centralized system that feeds both Shopify and marketing feeds, ensuring the data is identical everywhere.
2. In Shopify: Use Product Metafields at the variant level to store gtin and mpn. Metafields are custom fields that allow storing additional structured attributes, making it easier for feed apps and ERPs to read the correct data without having to "scan" the description or title.

Implementation Example: Create a gtin_text text attribute per variant in the PIM. Map it in the integration to populate the shopify.metafields.product.gtin metafield. Upon export, the feed will read this metafield.

Source: Guide to managing identifiers in Shopify.

How to Map GTIN/EAN in Feeds and Transformation Rules

A feed is the file (XML, CSV) or API that sends your products to external channels. Clear mapping rules at this stage prevent automatic errors.

Recommended Transformation Logic: In your export pipeline (feed management tool), always prioritize the gtin field coming from the PIM/Metafield. Implement a "fallback" rule:

1. If gtin is not empty → Use gtin.
2. If gtin is empty AND mpn exists → Use mpn and mark identifier_exists = false (if applicable according to the category).
3. Normalization: Before sending, apply a function that removes whitespace, dashes, and validates that there are only numeric characters.

Transformation Pseudorule: IF gtin IS NOT EMPTY THEN map_to 'gtin' ELSE IF mpn IS NOT EMPTY THEN map_to 'mpn' AND set 'identifier_exists' to 'false'.

Typical Error: Sending "dirty" GTINs (e.g., 123-456-789) which cause the total rejection of the item in the feed due to invalid format.

How to Build Your Identifier System: Sourcing, Rules, and Data Model

The EAN Code is critical not only for Google but for maintaining operational coherence between your store, your ERP, and marketplaces (Amazon, Zalando, etc.). Here we delve into governance: how to obtain them, how to decide their inheritance, and how to structure the data.

Key Initial Rules for Governance

Without a documented policy, every department (purchasing, logistics, marketing) will apply different criteria. This guarantees duplicates.

The Minimum Viable Policy: Document when it is mandatory to use a GS1 GTIN and when an internal identifier is allowed.

• Rule: If the product is sold on marketplaces or external feeds, require a registered GTIN from GS1.
• Rule: Private label products that will never leave the own website can use internal identifiers, but must be internally tagged as local_only to exclude them from GTIN requirements in feeds.

Resource: GS1 is the only authorized source for generating interoperable codes. Consult their standards at GS1 Standards.

Rules by Variant and EAN Inheritance

The decision to apply the EAN to the "parent" product or to the "child" variants is the source of greatest friction in fashion catalogs and complex variants.

Decision Framework:

1. Simple Product: The GTIN is assigned to the product.
2. Variants (Size/Color): Each variant sold separately must have its own GTIN. A size 10 sneaker and the same one in size 11 are distinct physical products with distinct barcodes.
3. Bundles / Multipacks: If you sell a pack of 3 units, this needs a new GTIN (for the pack); you cannot reuse the individual unit's one.

Inheritance Logic in Export: Configure your feed to look for the value in this order: Variant > Product. If the variant has a GTIN, use it. If not, check if the parent product has one (only valid for simple products).

Typical Error: Using the same GTIN for all sizes of a t-shirt. Google will detect that the same identifier points to different SKUs and will reject all of them for "Duplicate GTIN".

Obtaining Valid EANs and Traceability

Advanced marketplaces may audit the ownership of the GTIN prefix.

Obtaining Process: Buy blocks of GTINs directly from GS1 for the countries where you operate. Avoid resellers of cheap codes, as they often belong to other companies and will generate brand conflicts on Amazon or Google.

• In the PIM: Record not only the number but the source. Add administrative fields: gtin_source, date_assigned, and validation_status.

Multipacks and Special Cases

A multipack is a sales unit distinct from its components.

How to Manage It: Assign a unique GTIN to the pack. In the PIM, create a "contains" relationship linking the pack SKU with the quantity of the base SKU.

• In the feed: Mark the multipack attribute as true (or indicate the quantity) and export the pack's GTIN.
• Example: Pack of 6 bottles of wine. It has its own EAN-13 on the box. Do not use the individual bottle's EAN.

Audit and Correction at Scale: Automated Checks and Shipping Checklist

Even with good policies, data degrades. This section covers how to audit your catalog massively before critical dates (Black Friday, Sales) to ensure no "top seller" is rejected due to EAN problems.

Massive Prior Validation of EAN Code

Incorrect codes generate silent rejections: the product uploads, but receives no impressions.

Batch Validation Strategy: Extract a complete dump of your catalog (CSV/Excel) with the columns: sku, variant_id, gtin, mpn, and identifier_exists. Run a script or use formulas to validate:

1. Length: Does it have 8, 12, 13, or 14 digits? Anything else is an error (unless it is an ISBN).
2. Type: Is it numeric?
3. Integrity: Validate the check digit using the Modulo 10 algorithm.

Produce a report with three columns: status (Valid/Invalid), reason (Incorrect Checksum/Wrong Length), and action (Correct in PIM).

Typical Error: Applying manual corrections in the feed (for example, adding a leading 0 to convert UPC to EAN) without correcting the data in the PIM, which perpetuates the error in future synchronizations.

Correct Use of the identifier_exists Attribute

Google and Meta allow products without GTIN, but only if you use this attribute correctly. Misuse (marking everything as false to avoid looking up codes) can lead to account suspension.

Assignment Logic:

• If gtin is present and valid → Export gtin.
• If gtin is empty AND the product is "custom" (craft, private label without GTIN, antique) → Export identifier_exists = false.
• Ensure this logic applies at the variant level. Variant A might have a GTIN and variant B (a limited handmade edition) might not.

More Info: Consult the product data specification from Google and the catalog documentation from Meta.

Operational Checklist Before Production Shipment

Follow this protocol before connecting a new feed or after a massive catalog update:

1. Format Validation: Do 100% of populated gtin fields pass the length and checksum test?
2. Family Review: Are identifiers assigned to variants and not the parent in configurable products?
3. Metafield Map: Confirm that the feed is reading shopify.metafields.namespace.key and not the description?
4. Test Send: Upload the feed to a "Test Feed" in Merchant Center to see errors without affecting the live account.
5. Change Log: Record in the PIM who modified a GTIN and why, to maintain traceability.

Automating Catalog Governance with ButterflAI

Maintaining EAN/GTIN identifier integrity manually across thousands of SKUs is a task prone to human error and consumes hours of technical management.

ButterflAI audits your catalog in real-time, detecting inconsistencies in identifiers, validating checksums, and ensuring the variant structure meets strict Google Merchant Center and Meta requirements. The platform allows for massive correction of these attributes and generates optimized descriptions and metadata, guaranteeing your products are not only approved but also positioned better.