Glossary
How does Meta's ad auction pick a winner?
Melvin Salas1 min readVerified 10 October 2026
Short answer
Each time there's an opportunity to show an ad to someone, Meta runs an auction to decide which ad to show. Meta says the winner is the ad with the highest total value, subject to a price floor that may affect whether an ad is shown and the price paid, and that total value is a combination of three major factors: the bid, estimated action rates and ad quality.
Meta defines the three. The bid is what the advertiser is willing to pay to achieve their desired outcome. Estimated action rates are an estimate of whether a particular person engages with or converts from a particular ad. Ad quality is a measure of the quality of an ad as determined from many sources, including feedback from people viewing or hiding the ad and assessments of low-quality attributes in the ad, such as withholding information, sensationalised language and engagement bait.
Meta says that together, estimated action rates and ad quality measure ad relevance, and that because these are components of the auction, an ad that's more relevant to a person could win an auction against ads with higher bids. The ads eligible to compete are those with a target audience the person belongs to, and Meta notes that one person can fall into multiple target audiences.
Meta also says it may make adjustments that could affect auction outcomes and prices, and that such auction adjustments will not cause it to charge you more than your bid to show your ad.
Our reading, not Meta's: the auction runs on estimates made for each person at the moment of the auction, while ad relevance diagnostics report how an ad did over a date range, and Meta says those diagnostics aren't inputs into the ad auction. A ranking column is a report on the ad, not the lever that set its price.
Reading these columns is daily work for us
Riibon watches every campaign daily and holds a baseline for each metric, so a move in impression share or Quality Score is judged against what is normal for that account, not against a rule of thumb, before anyone acts on it.
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