What Meta says
In Meta's own words: “When you create ad sets with overlapping audiences, multiple ads from your Page may enter the same ad auction. We call this auction overlap.” (Meta help center)
Why running five campaigns can hurt
When your ad sets chase the same people, Meta will not bid against you twice; it picks one and holds the others back. The result is fragmented conversion signal, each ad set starved of the volume it needs to exit the learning phase, and often higher costs. More campaigns is not more reach when they fish the same pond.
The fix is consolidation
Fewer, broader ad sets under Advantage+ campaign budget usually beat many narrow overlapping ones. You can check the audience overlap tool before launching, and consolidate when you see the same audience split across ad sets. One campaign that clears the learning threshold beats five that never do.
A worked example
Say you run two ad sets at $50 a day each, one targeting a 1,000,000-person interest audience and one a 100,000,000-person broad audience, and Meta's overlap tool shows 800,000 people in both. That is 80% of the smaller audience but only 0.8% of the larger one, so the smaller ad set is the one that keeps losing its place in the auction. Merging them into one ad set at $100 a day puts all the conversions behind a single learning phase instead of splitting them.
Common questions
How do I know if my ad sets overlap?
Meta's audience overlap tool compares audiences directly, and signs of trouble include ad sets stuck in learning and rising costs when you add more of them. Overlapping targeting is the usual cause.
Does running more campaigns get more reach?
Not if they target the same audience. They compete in the same auctions, so Meta suppresses one and splits your signal. Consolidating usually reaches more people more efficiently.
Does auction overlap happen across different ad accounts?
Yes. Meta says running ads from separate ad accounts may not help you avoid overlap, because the delivery system can identify multiple accounts as the same advertiser. Its first suggested fix is consolidating campaigns into fewer accounts.
Which ad does Meta enter when my ads overlap?
When two or more of your ads enter the same auction, Meta enters the one with the highest total value and does not consider the others in that auction, so your ads never bid against each other.
How does Meta's audience overlap tool work?
In Audiences, tick up to 5 saved or custom audiences and choose Actions, then Show audience overlap. Meta says it only gives useful results for audiences of at least 10,000 accounts, and the overlap percentage changes depending on which audience you select as the base.