What is CSS on Google Shopping and why is it important for your e-commerce business?

Do you use Google Shopping to sell your products online? You’ve probably heard of Google Merchant Centre, Google Ads, product feeds… But did you know that a little-known technical tool, CSS, plays a crucial role in the performance of your campaigns?

Long overlooked, this lever has proven to be strategic since European regulations forced Google to open its ecosystem to competition. Today, choosing the right CSS can help you reduce your acquisition costs, gain visibility, and regain control over an entire section of your Shopping campaigns. Here’s why.

CSS, a key player in Google Shopping

Behind every sponsored product listing on Google Shopping is a CSS, or Comparison Shopping Service (French: Service Comparateur de Prix). This is not a consumer-facing platform, but rather a technical intermediary that relays your products to Google, between Google Merchant Centre and the search engine. Without CSS, your Shopping ads simply cannot appear.

CSS is visible and may have a slight impact on consumer behaviour. In Google Shopping ads, a note indicates ‘by [CSS name]’ at the bottom right of the ad. This visual detail reveals a strategic choice made by the advertiser.

In France, the majority of advertisers choose to use Google Shopping CSS (source: 2024 report by Producthero). This choice is mainly explained by the fact that advertisers wanted to be sure that their products would continue to be advertised following the change in the ecosystem; Google was therefore the obvious choice. However, this choice is not always the most effective… nor the most profitable.

Why other CSSs were allowed to compete with Google

In 2017, the European Commission condemned Google for abusing its dominant position in the price comparison market. By favouring its own Shopping ads in search results, Google was stifling competition from other comparison sites. The result: a record fine of €2.42 billion and the obligation to open up its advertising system to independent CSSs in Europe, Switzerland and the United Kingdom.

Since 2018, e-merchants have been able to choose between Google Shopping CSS and around twenty certified partner CSSs. This has opened up the market to players such as Kelkoo, Shoparize, Channable and Producthero, who now offer merchants the opportunity to distribute their Shopping ads via their services.

The real issue: why switching to third-party CSS changes everything

When using Google Shopping CSS, once the bid has been placed and if there is a click on the advertisement displayed by Google Shopping CSS, the customer is charged the bid amount and 20% CPC.

With the same Google Shopping budget, using a third-party CSS increases the number of clicks on your adverts. This is an immediate optimisation, without changing your campaigns or feeds. Everything is still managed in your Google Ads and Merchant Centre accounts as before. Only the ‘pipe’ that connects your products to Google changes.