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When shoppers search for products on Google, they can see relevant shopping ads for offers from many stores. To participate in shopping ads in countries where the CSS program is available, a merchant must be represented by a comparison shopping service, also known as a CSS (Comparison Shopping Services), or with several CSSs.
Each CSS offers different services and different pricing models. Some charge their customers per click.
All comparison shopping services compete for ad space equally, including Google Shopping. The placement of the ad depends on a few factors. Ads need to follow the same basic rules designed to make them helpful to users. Each CSS bids in an auction how much they would be willing to pay for an ad click to your website who wins the auction depends on the bid, quality, and relevance of the ad.
