A Comparison Shopping Service (CSS) is a website that allows users to search for and compare products, then redirects users to retailer sites to make purchases. In the European Economic Area and Switzerland merchants must work with one or more CSSs to begin placing Shopping ads.

CSSs work with online retailers to showcase their product offers on the CSS’s website. They offer various features to consumers, allowing them to search for and compare products offered by a range of shops.

Most CSSs also advertise their partners’ products on other channels to generate leads for them. Shopping ads on Google’s general search results pages is one channel CSSs manage on behalf of their customers. Some CSSs generate leads for you across a multitude of channels, while others offer programs dedicated to specific channels, including Shopping ads.