A feed specification is the published list of product attributes a shopping channel accepts, with what each one means, which ones are required and the format each value has to follow. For Google it is the product data specification for Merchant Center. Meta and Microsoft publish their own, with similar but not identical rules.
How a feed specification works
Google groups its attributes into sets. Basic product data covers the ID, title, description, product page link and main image link. Price and availability cover the price, any sale price and whether the item is in stock. Categorisation covers Google’s product category and your own product type. Identifiers cover brand, GTIN and manufacturer part number. Detailed attributes cover condition, size, colour, material, gender and age group. Campaign attributes cover the custom labels you use to organise bidding.
Each attribute has format rules. A few examples from Google’s specification:
- Titles can be up to 150 characters and descriptions up to 5,000.
- Product IDs can be up to 50 characters and must stay the same for the same item over time.
- Prices need a currency code, for example 24.99 GBP, and sale prices should carry start and end dates if the offer is time-limited.
- Availability takes set values such as in stock, out of stock or preorder.
Some requirements depend on the country and the product. Clothing sold to UK shoppers needs colour, size, gender and age group. Used or refurbished items need a condition value. Products with no manufacturer barcode, such as handmade goods, declare that no identifier exists rather than leaving the field empty.
Why it matters
The specification is effectively the contract between you and the channel. Missing a required attribute gets the product disapproved, while missing recommended ones limits how often it appears. For UK shops there are a few local points to get right: prices in pounds including VAT, and delivery costs supplied either in the Merchant Center shipping settings or in the feed.
Complete data also changes how a listing looks. Google can only show details such as size options, delivery cost or a sale price in a result when the matching attributes are present and correct, and those details are often what makes a shopper choose one listing over the one beside it.
Google revises the specification from time to time, usually with notice. A feed that was compliant two years ago may now be missing something a newer feature relies on.
Common mistakes
- Assuming the ecommerce platform’s Google plugin produces a compliant feed without checking the diagnostics.
- Using one feed for every channel, even though Meta’s catalogue fields and rules differ from Google’s.
- Running a sale price with no end date, so the feed keeps claiming a discount after the offer has ended.
- Reusing one GTIN across several variants, or entering a made-up number.
- Filling only required attributes and skipping recommended ones that help matching, such as product type and material.
How to act on it
Download your current feed into a spreadsheet and compare it with Google’s specification column by column for your main category. Fix required attributes first, then add the recommended ones that reflect how people search for your products, using the right Google product category for each range.
Each quarter, check the Merchant Center Help Center for announced changes to the product data specification. When I set up or audit Shopping and Performance Max campaigns, checking the feed against the current specification comes before any bidding work, because no bid strategy can make up for missing data.