## Identifiers

### Introduction/Business Impact

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Product identifiers are essential for your merchants to define the product they are selling in the global marketplace. They uniquely distinguish products merchants are selling and help match search queries with their products. Identifiers are used to match against Google's product catalog to ensure product validity.

In addition, it allows your merchants to leverage Google's catalog to be able to have the richest data to maximize the number of clicks and impressions.

### Tech Guidance

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#### Understanding which product identifiers are most important

To ensure validity for each product, include unique identifier attributes in the [Product identifiers](https://support.google.com/merchants/answer/160161) group for each product. Unique identifiers include:

- The product's [Global Trade Item Number (GTIN)](https://www.gtin.info/), also known as a Universal Product Code (UPC). We recommend for merchants to prioritize providing this identifier to expect the best potential results ![gtin](https://developers.google.com/static/merchant/storebuilder/images/blueprint/gtin.png)
- [Manufacturer part number](https://support.google.com/merchants/answer/6324482) (MPN)
- [Brand](https://support.google.com/merchants/answer/6324351)

> [!IMPORTANT]
> **Important:** GTIN is required if the condition is new, availability is in stock or out of stock, or the merchant is not the unique seller.

#### Implementation of products with identifiers

If a product has a unique identifier, you can pass this data on behalf of the merchant to the corresponding identifier attribute. If the initial value provided is incorrect, there will be a product disapproval which will appear and the merchant should have the ability to fix this through their product catalog.

#### Implementation of products without identifiers

If a product doesn't have assigned product identifiers that meet the [requirements](https://support.google.com/merchants/answer/6324478), then leave it blank. This will trigger the item demotion or disapproval, which should drive the merchant to update the corresponding identifiers where [*Offer Level Errors and Warnings*](https://developers.google.com/merchant/storebuilder/online/sections/3_2_1_errors_and_warnings) appear.

There is a field called [`identifier_exist`](https://support.google.com/merchants/answer/6324478), we recommend not to use this because it doesn't drive merchant action to update the necessary identifiers.