Definition
A Comparison Shopping Service (CSS) is an approved third party that Google authorises to serve a merchant's Shopping ads on Google's comparison shopping results pages, instead of Google acting as its own comparison shopping service.
Why it matters to merchants
When Google acts as its own CSS (the default arrangement), it charges a premium cost per click (CPC) on Shopping ads. By switching to an approved CSS provider, merchants typically reduce their Google Shopping CPC by roughly 20 to 30% with no change to the products being advertised or the visibility they receive.
This CPC reduction applies directly to your advertising spend. If you currently spend £1,000 per month on Google Shopping ads and switch to a CSS, you could expect to pay around £700 to £800 for the same volume and quality of clicks.
The reduction happens because Google's own CSS charges a markup on advertising costs. An independent, approved CSS provider does not apply this markup, passing the savings to you.
How it works in practice
Enrolling with an approved CSS is straightforward. You connect your Google Merchant Center account to the CSS provider's platform. Your product data and Shopping ads continue to run exactly as before: Google still displays your products on comparison shopping results pages, and your feed remains in Google Merchant Center.
The only difference is the routing. Instead of Google serving your ads through its own CSS, the approved third-party CSS handles the serving. Your click volume, product visibility, and ad quality remain unchanged. You simply pay the lower CPC rate.
On Vendably, CSS enrolment is free and requires no subscription. You pay only for the clicks you receive, at the reduced CPC rate.
Related terms
Google Merchant Center: The Google platform where you upload and manage your product feed. Your Merchant Center account connects to a CSS provider to enable the CSS relationship.
Google Shopping: Google's shopping comparison service where your ads appear when users search for products. A CSS serves these ads on your behalf.
Product identifier: A unique code (such as gtin, mpn, or sku) that identifies each product in your feed. Accurate product identifiers help Google and your CSS provider match your products correctly.