If you use paid search, you’ve probably wondered how Google decides which ad should be at the top, and what order the rest of them are shown in. In Chapter 9, we learned how a ranking algorithm with with a set of ranking factors sort paid search ads. While each paid search engine uses different algorithms for their paid search rankings, Google maintains the most complete explanation of how its algorithm, called AdRank, works:

Microsoft doesn’t regularly maintain information about its ranking algorithm but did publish a blog post a few years ago on BingAds ranking algorithm.