Blog post — Merchant Audit

Product identifiers are the bedrock of successful Google Shopping campaigns. Without accurate and complete product data, your products risk limited visibility or outright disapproval. Understanding the nuances of GTIN, MPN, and Brand is crucial for any merchant aiming to maximize their reach on Google's powerful shopping platform.

What Are Product Identifiers and Why Do They Matter?

Product identifiers are unique codes that distinguish specific products globally. Google uses these identifiers to understand what product you're selling, group similar products from different merchants, and match user queries with the most relevant listings. This aggregation allows Google to offer a richer, more competitive shopping experience for consumers. Ignoring or incorrectly submitting these attributes—GTIN, MPN, and Brand—can lead to low impression share, reduced click-through rates, and, most critically, product disapprovals.

Google's algorithms heavily rely on these identifiers to present the most accurate and competitive product information. When your products lack proper identifiers, Google's ability to categorize and display them diminishes, directly impacting your advertising performance. Think of them as your product's passport; without it, it can't travel across borders—or in this case, Google's feed.

GTIN: The Global Trade Item Number Explained

The Global Trade Item Number (GTIN) is a globally unique and recognized identifier for products. These are often called UPC (North America), EAN (Europe), ISBN (books), or JAN (Japan). GTINs are assigned by international organizations like GS1 and are found on product packaging, usually near the barcode.

When is GTIN required for Google Shopping?

For all new and "condition=new" products with a GTIN assigned by the manufacturer. This is non-negotiable for most branded products. If the manufacturer provides a GTIN, you must include it.
If you are reselling a product that originally had a GTIN. Even if you're not the manufacturer, the product's original identifier still applies.

When can you omit GTIN or use identifier_exists=false?

There are specific scenarios where a GTIN is either not required or simply doesn't exist for your unique product:

Custom-made or handmade products: Items like custom jewelry, unique art pieces, or made-to-order furniture typically don't have a GTIN.
Vintage or antique items: Products that predate the systematic assignment of GTINs.
Parts for original equipment manufacturers (OEMs): If sold directly by the OEM without a retail package GTIN.
Store brand products that don't have a GTIN.
Books published before ISBN was assigned.
Bundles: If you've created a bundle of multiple products, the bundle itself generally won't have a GTIN (though the individual items in the bundle should).
Products without retail packaging, such as bulk goods.

If your product falls into one of these categories and genuinely does not have a GTIN, you must submit identifier_exists=false in your product feed. Do not submit a false GTIN or leave the attribute blank for products that should have one. Google will flag these, leading to warnings or disapprovals. Using identifier_exists=false for products that do have a GTIN is a common mistake that can sever product visibility.

MPN: Manufacturer Part Number

The Manufacturer Part Number (MPN) identifies a product among all products from the same manufacturer. Unlike GTINs, MPNs are unique only within a specific manufacturer's range, not globally. For example, two different manufacturers might coincidentally use the same MPN for distinct products.

When is MPN required for Google Shopping?

For all products without a GTIN. If your product doesn't have a GTIN (and identifier_exists=false is used), Google strongly recommends, and often requires, the MPN along with the Brand.
Highly recommended for all products, especially if the GTIN isn't unique or is missing. Providing both GTIN and MPN, when available, gives Google more data points to identify your product accurately.

Best Practices for MPN:

Always use the exact MPN provided by the manufacturer.
Combine MPN with the Brand attribute for maximum accuracy, especially when no GTIN is present.
Avoid using internal SKUs or arbitrary numbers as MPNs, unless they are genuinely the manufacturer's part number.

Brand: Who Made It?

The Brand attribute identifies the manufacturer or brand of your product. This is a fairly straightforward attribute but is equally critical.

When is Brand required for Google Shopping?

Always required for all products, if a brand exists. Even for products without a GTIN or MPN, the brand is usually present.
If you are the manufacturer of custom or handmade products, use your store name or brand name.

Best Practices for Brand:

Use the official, recognized brand name.
Be consistent with capitalization and spelling across all your products from that brand.
Do not include marketing slogans or additional descriptive text in the brand field.

The Triad: GTIN, MPN, and Brand Together

Google's identification system works best when you provide as much accurate data as possible. Here’s a quick guide to their interplay:

Scenario	GTIN	MPN	Brand	`identifier_exists`	Notes
Branded product (most common)	Required	Recommended	Required	Omit/False	Provide accurate GTIN. MPN and Brand improve matching.
Product with no GTIN assigned	Omit (empty)	Required	Required	`false`	MPN and Brand become primary identifiers.
Custom/handmade items	Omit (empty)	Omit (empty)	Required	`false`	Your brand/store name is used.
Used/refurbished branded product	Original Req.	Original Rec.	Original Req.	Omit/False	Even if condition isn't new, original identifiers are still relevant.
Bundles of branded products	Omit (empty)	Omit (empty)	Your Brand	`false`	Individual items in bundle should still follow their own identifier rules.

Note: "Omit/False" for identifier_exists means that you either don't include the identifier_exists attribute (which defaults to true) or you explicitly set it to false if GTIN, MPN are truly missing and the product requires it.

The sweet spot for Google is to have a GTIN. If absent, the combination of MPN and Brand steps in as your product's identification backbone. Failing to provide these, or providing incorrect data, significantly degrades your product's visibility.

Common Product Identifier Mistakes

Merchants often stumble on product identifiers, leading to preventable disapprovals or lost impressions.

Submitting incorrect GTINs: Using a GTIN from a similar product or an internal SKU instead of the manufacturer's GTIN.
Using identifier_exists=false incorrectly: Applying this flag to products that do have a manufacturer-assigned GTIN. Google will typically disapprove these or penalize their visibility.
Missing required identifiers: Simply leaving GTIN, MPN, or Brand blank when they are mandatory for a product.
Inconsistent Brand names: Using "Nike" for one product and "Nike, Inc." for another from the same brand.
Using arbitrary strings for MPN: Not using the official manufacturer part number.

These errors are often difficult to spot manually, especially with large product catalogs. Tools like Merchant Audit can automatically scan your Shopify/WooCommerce store and detect these subtle but critical errors across your product feed, schema, and trust signals. This proactive approach ensures your product data remains compliant and your campaigns perform optimally.

Ensuring Accuracy and Compliance

Maintaining accurate product identifiers requires attention to detail, particularly as your product catalog grows.

Always refer to the manufacturer's packaging or documentation for the correct GTIN and MPN.
Integrate identifier fields into your product data entry process. Make it a standard practice to record these details for every new product.
Regularly audit your product feed. Check for missing identifiers, incorrect identifier_exists flags, and brand consistency.
Leverage automated tools. For larger stores, manually verifying every GTIN, MPN, and Brand is impractical. Solutions like Merchant Audit specialize in identifying Google Merchant Center compliance issues, including identifier discrepancies, allowing you to quickly rectify problems before they impact your sales.

By meticulously managing your GTIN, MPN, and Brand attributes, you provide Google with the precise information it needs to display your products effectively, leading to better ad performance and fewer disapprovals.

FAQ

Q1: Can I just generate my own GTINs for my products?

A1: No, you should never generate your own GTINs. GTINs are assigned by GS1 and are globally unique. Using self-generated or fake GTINs will result in product disapprovals and may lead to account suspension. Only use GTINs provided by the actual manufacturer.

Q2: What if my product has a GTIN, but I still want to submit `identifier_exists=false`?

A2: You should never submit identifier_exists=false for an item that has a GTIN. Google will see this as conflicting information, likely disapprove your product, and significantly limit its visibility. Always provide the correct GTIN if one exists.

Q3: My product is branded, but the manufacturer doesn't provide an MPN. What should I do?

A3: If the product genuinely does not have an MPN from the manufacturer, leave the MPN attribute blank. Just ensure you provide the correct GTIN and Brand. The MPN is highly recommended but not always strictly required if a GTIN is present.

Ensure your product identifiers are always accurate to keep your products visible and eligible on Google Shopping.