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Comparison Shopping Service (CSS)

A Comparison Shopping Service (CSS) is a comparison website that places stores' Shopping ads on Google in 21 European countries, including the UK and Switzerland.

How it works

In 21 European countries, Czechia and Slovakia among them, only a CSS can place Shopping ads on Google’s general search results. Ukraine is not on the list. Google’s own CSS, Google Shopping, bids for its stores like any other CSS. A store can use one CSS or several at once.

The CSS gets a Merchant Center account for your store and submits your products through it. One Merchant Center account can belong to only one CSS.

Because the European Commission requires Google Shopping to be profitable on its own, it deducts a fixed percentage margin from each bid before the auction. Your cost per click (CPC) includes this margin. Google does not publish the percentage, and other CSSs set their own fees. To check the effect on your account, see testing a CSS switch.

Where you see it

  • On the ad: a “By …” link at the bottom names the CSS that submitted the offer.
  • Merchant Center: Settings → General → Comparison Shopping Services lists every CSS that has uploaded your products.

Example

Example store, not client data.

The tableware shop sells in Czechia: 40,000 a month buys 8,000 clicks, a CPC of 5. It moves to another CSS with a fee of 1,000 a month. The next month, the same 40,000 buys 8,500 clicks: 40,000 ÷ 8,500 = 4.71 per click. With the fee, (40,000 + 1,000) ÷ 8,500 = 4.82, or 3.5% less than before.

Not to be confused with

  • Price comparison engine — a site where shoppers compare offers, and the store usually pays per click there. A CSS places your ads on Google.
  • Shopping campaign — the Google Ads campaign type. Google Shopping, the CSS, only shares the name.

Right and wrong readings

  • Wrong: “A CSS makes every click 20% cheaper.” Right: Google does not publish its margin, and the new CSS charges a fee. In the example, the saving after the fee is 3.5%.
  • Wrong: “Two CSSs will bid against each other and raise our CPC.” Right: Google says a merchant is never second-priced against itself: its own bids never raise its CPC.

Sources