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Comparison Shopping Services (CSS): Why UK and European Stores Should Use One

How a Comparison Shopping Service places your Shopping ads in the UK, Switzerland and the EEA, why using one other than Google Shopping can lower what you pay per click, and how to choose and switch.

Curated byTerry Ecom (opens in a new tab)

Updated

What a CSS is

In the UK, Switzerland and much of the European Economic Area, Shopping ads and free product listings on Google can only be placed by a Comparison Shopping Service (CSS). Every store selling in those countries already uses one: if you never chose, it's Google Shopping, which is Google's own CSS and bids for merchants just like any other.

The countries in Google's CSS program are Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland and the United Kingdom.

Why it can lower your cost per click

Google Shopping has to be independently profitable in the EEA, so Google says it deducts a fixed percentage margin from each bid placed through it before the bid enters the auction. That margin is often quoted at around 20%, though Google doesn't publish the figure. Other CSSs don't take that margin out of your bid, so the same budget can enter the auction at a higher bid.

What you actually save per click depends on the auction: you still pay only what's needed to beat the next bidder, and the CSS charges its own fee on top. Compare the total cost and the sales you get, not the headline saving. All CSSs, including Google Shopping, compete for the same ad space, and no space is reserved for any of them.

What stays the same

  • Your Google Ads account doesn't need to be switched. The CSS is set on your Google Merchant Center account, and any campaign using its products, including Performance Max, runs through that CSS.
  • You can keep your own Google Ads account, campaigns and bidding. In a self-service or hybrid setup you keep running everything yourself.
  • Your ads follow the same Shopping ads policies and product data rules, and clicks still go straight to your product pages.
  • Using several CSSs at once won't make you bid against yourself: Google says a merchant is never second-priced against itself.

What changes

  • The "By ..." link at the bottom of your Shopping ads names the CSS that placed them instead of Google, and clicks on it go to that CSS's own site.
  • The CSS invoices you instead of, or as well as, Google, depending on the setup you agree.
  • Your ads also have to be shown on the CSS's own comparison site.
  • Some CSSs only place ads in the Shopping unit on Google search. Others also opt in to the Shopping tab, YouTube, Display and dynamic remarketing. If yours doesn't, products stop showing on those surfaces.

How to choose a CSS

Google lists approved CSSs on its Comparison Shopping Partners site, where you can filter by country, industry and language. Pick one approved in every country you sell to, then compare:

  • How it charges: a flat monthly fee, a markup or share of your click costs, a fee per click, or a commission on sales.
  • Whether you keep running your own Google Ads account and feed (self-service), or the CSS runs them for you (managed). With a managed service you usually lose direct access to the accounts.
  • Whether it needs a copy of your product feed or works from your existing Google Merchant Center account.
  • Which surfaces it places ads on beyond Google search, and whether it serves countries outside the CSS program if you sell there too.
  • Whether it puts your Google Merchant Center account under its own multi-client account. If it does, that account's users get access to yours, so check who that includes.
  • How you leave: notice periods, minimum terms and whether it will release your account promptly.

How to switch, and switch back

To keep your existing Google Merchant Center account, ask the new CSS to start the switch. An admin of your account approves it, and the move takes effect after a grace period of up to 14 days, during which you can still change your mind. An account works with one CSS at a time.

Switching back works the same way, including back to Google Shopping. You can also see which CSSs advertise your products, and turn any of them off, from the Comparison Shopping Services dashboard in Google Merchant Center.

  1. Pick an approved CSS for your countries and agree the setup and fee.
  2. Ask it to request the switch for your Google Merchant Center account ID.
  3. Approve the request in Google Merchant Center and check the account access settings it asks for.
  4. After the grace period, check your campaigns are serving and the CSS shows on your dashboard.

How UltraROAS.ai does this for you

UltraROAS.ai is not a CSS and doesn't change which CSS you use. It works through the Google Ads and Google Merchant Center accounts you connect, so campaigns it builds and fixes it makes run through whichever CSS your Google Merchant Center account uses, and you never need to switch CSS to use it.

Try it freeFree plan, no card: see everything Optimize would change before you pay.

Questions

Do I need a CSS to run Shopping ads in the UK?
Yes, but you already have one. If you haven't picked another, Google Shopping places your ads as your CSS.
Is a 20% saving guaranteed?
No. Google Shopping keeps a margin on bids placed through it, often quoted at around 20%, but your saving per click depends on the auction and on what the CSS you choose charges.
Will I lose my campaigns' history if I switch?
No. Your Google Ads account isn't switched, so campaigns and their history stay where they are. Only the Google Merchant Center account's CSS changes.
Does a CSS work with Performance Max?
Yes. Google says Performance Max can be used with any CSS you work with in CSS program countries.

Google's own help pages

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