Quality Score vs Ad Rank: What's the Difference?

Quality Score is Google's 1-10 rating of how relevant an ad is, based on expected click-through rate, ad relevance, and landing page experience. It's shown in the account as a diagnostic metric - useful for spotting weak ad groups - but it is not the exact figure plugged into the live auction anymore.

Ad Rank is the real, auction-time value that decides two things: whether an ad shows at all, and what position it gets. It's calculated from the bid, quality factors, and auction-time signals such as ad extensions and the context of the search, and it directly determines the actual CPC paid, based on the Ad Rank of the ad sitting just below it.

The relationship between the two is easy to misstate. A better Quality Score generally correlates with a better Ad Rank at a lower cost, since quality is one of the inputs. But they are not interchangeable - Quality Score is a reporting tool for diagnosing why an ad might be underperforming, while Ad Rank is the mechanism that actually runs the auction. Chasing a higher Quality Score number in isolation, without checking whether it moved position or cost, misses the point of tracking it at all.