In the UK, the EEA and Switzerland, Shopping ads are placed through Comparison Shopping Services. Google Shopping is one of them. Since the European Commission’s 2017 decision, merchants can have their ads submitted by another certified CSS instead, with the same campaigns and the same auction.
Where the difference comes from
When Google Shopping places your ad, it keeps a share of what you bid before the remainder enters the auction. Industry sources describe that share as roughly 20%. When a partner CSS places the ad, the partner sets its own charges, and several UK partners charge nothing or a flat fee. The result is that more of each bid reaches the auction.
This is not a rebate paid to you. It shows up as lower cost per click at the same position, or more impressions at the same cost. How much you see depends on the competition for your products, so treat 20% as the mechanism, not a guaranteed saving.
What stays the same
- Your Google Ads account, campaigns, bid strategies and budgets.
- Your product feed and Merchant Center product data.
- Your landing pages and the customer’s experience.
What changes is the small label under the ad, from “By Google” to the partner’s name, and the association between your Merchant Center account and the CSS. Performance Max and Standard Shopping campaigns both run through whichever CSS is associated.
Where it applies
The CSS programme covers the UK, the EEA countries where Shopping ads run, and Switzerland. It does not exist in the United States, Australia or other markets, so a store selling worldwide only benefits on its European traffic. Irish stores are covered through the EEA.
How to check before and after
- Record average cost per click, impression share and cost per conversion for your Shopping campaigns over the previous four weeks.
- Associate your Merchant Center account with the partner CSS. No campaign changes.
- Leave bids and budgets untouched for two weeks.
- Compare the same metrics. The clearest signal is cost per click for the same products at similar impression share.
Questions to ask a CSS partner
- What do you charge, and is anything tied to my ad spend?
- Do I keep full ownership of my Google Ads and Merchant Center accounts?
- Can I leave, and what happens to the association when I do?
- Do you also manage campaigns, and is that optional?
A CSS switch is a one-off structural gain. It does not fix a weak feed, poor margins or a campaign that is buying the wrong demand. Do it, measure it, then move on to the things that compound.
Platform features and requirements change. Check the current Google and Meta help pages for your account before relying on a specific setting. Nothing here is legal advice; confirm consent and tax treatment with your own advisers.
Questions owners ask
What is a Google CSS?
A Comparison Shopping Service is a company certified by Google to place Shopping ads on behalf of merchants. In the UK, EEA and Switzerland, Google Shopping itself is one CSS among many, and merchants can choose which one submits their ads.
Does switching CSS change my campaigns?
No. Your Google Ads campaigns, bidding and product data stay as they are. The Merchant Center account is associated with the CSS partner, and the small label under the ad changes from “By Google” to the partner’s name.
Will I really save 20 percent?
You keep more of each bid in the auction, which usually shows up as cheaper clicks or more traffic at the same bid. The exact effect depends on competition for your products, so measure cost per click and impression share before and after the switch rather than trusting a headline figure.
Put it into practice
Bring your store’s numbers to the conversation. We will start there.
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