Feed rules are instructions you set up inside Google Merchant Center that change your product data as Google processes it, without editing your website or the file your platform sends. They let you correct, fill in or reshape attributes, for example putting the brand at the start of every title or setting a custom label from a product’s price.
How feed rules work
Each rule targets one attribute, such as title, condition or custom_label_0. You tell it where the value should come from: an attribute in your primary feed, a column in a supplemental feed, or a fixed value you type in. Then you apply operations to it. The common ones are:
- Set to: replace the value, for example set condition to “new” for every product.
- Prepend or append: add text before or after, for example brand plus the existing title.
- Find and replace: swap words or characters, such as an internal abbreviation for the full product name.
- Extract: pull part of one attribute into another, such as a size from the title into the size field.
Conditions narrow a rule to certain products, so a rule can apply only where product type contains “dresses” or price is above £100. Rules run every time the data is processed, so they keep working when your platform refreshes the feed. Merchant Center lets you preview the result on sample products before you save, and where several rules affect the same attribute, their order matters.
At the time of writing (October 2026), rules are created from the settings of each product data source in Merchant Center, labelled attribute rules. Google has moved this menu before, so the path may differ in your account.
Why it matters
Many UK online shops run on Shopify, WooCommerce or similar platforms where changing product data at source is slow, needs a developer, or would change what shoppers see on the site. Rules give you a Google-specific version of the data without any of that. They are also the fastest way to fix a systematic gap, such as missing gender or age group on clothing, across hundreds of products at once, and to create custom labels for campaign structure from data you already hold.
Common mistakes
- Using rules to hide data that is wrong at source. A wrong price or stock level needs fixing in the shop, not masking in the feed.
- Adding promotional text such as “free delivery” or “sale” to titles, which breaks Google’s editorial rules for product data.
- Conditions that are too broad, so a rule meant for one range rewrites the whole catalogue.
- Stacking rules over months with no record of who added what or why.
- Forgetting existing rules when the platform changes its naming, which produces titles with the brand written twice or odd fragments.
How to act on it
List the issues in your Merchant Center diagnostics and decide, one by one, whether each should be fixed at source or by a rule. Anything about price, availability or what the product actually is belongs at source. Presentation, structure and missing descriptive attributes are good candidates for rules.
Build each rule with the narrowest condition that does the job, preview it on several products, and keep a short log of what each rule does. Review the rules every few months and after any change to your ecommerce platform. I check feed rules as part of ongoing Google Ads management for shops, because a broken rule can quietly damage every product at once.