Payment & Metrics
Audience Overlap
The share of audience shared between two campaigns or segments.
Audience overlap is the share of audience common to two campaigns, ad sets, or segments — the portion of users being targeted by both simultaneously. High overlap means your own campaigns compete against each other in the auction, driving up costs and muddying performance data as the same user sees, and is attributed across, multiple campaigns.
Buyers hit this when scaling horizontally on Meta or TikTok: duplicating ad sets with similar interest stacks or lookalikes creates internal competition instead of new reach. Platform tools expose overlap percentages between saved audiences; anything substantial argues for consolidation or exclusion rules. Overlap also corrupts test reads — two 'different' audiences that overlap heavily will produce converging results that tell you nothing. Exclude converters and existing customer lists everywhere as a baseline hygiene rule.
In buyer speech
“The two lookalike ad sets overlap something like 40% — merge them into one and let the algorithm sort delivery instead of bidding against ourselves.”