Ad spend is not only wasted by targeting the wrong audience. It can also be wasted when several ad sets repeatedly reach the same people. Audience overlap is the percentage of users who qualify for more than one active ad set. When two ad sets from the same Page are eligible for the same auction, Meta chooses the one with the highest Total Value. As Meta explains in its own guide to auction overlap, the other ad set does not compete for that impression. This prevents an advertiser from literally bidding against itself, but high overlap can still weaken performance. Similar ad sets divide the available impressions and conversion data between them. Instead of one ad set gathering enough information to optimize quickly, several ad sets receive smaller pieces of the same signal. LeadEnforce's research on overlap and performance explains how this can slow learning and make results less stable. Overlap of around 25% or more deserves attention, especially when the affected ad sets have similar objectives and creative. In many cases, combining ad sets with more than 30% overlap gives Meta a larger audience and a clearer set of conversion data. Adding more targeting layers often makes the problem worse by creating smaller groups with many of the same users. Before launching a new ad set, compare it with existing audiences in Ads Manager's Audience Overlap tool. bm2500 has a guide to reading the results and deciding when consolidation is appropriate.