The audience overlap tool everyone ignores

Meta's built-in audience overlap tool, which shows how much two saved audiences actually share the same users, sits unused in most ad accounts I audit, despite being free, built directly into the platform, and a direct explanation for one of the most common structural problems accounts have without realizing it.

Significant overlap between two campaigns' audiences means they're effectively bidding against each other in the same auction, each pushing up the other's costs while the platform's own algorithm has no way to know these two "different" campaigns are actually chasing largely the same pool of people.

The audit that catches this is a five-minute check most accounts never run: pull the overlap tool for every pair of active audiences targeting a similar funnel stage, and for anything showing meaningful overlap, either consolidate the campaigns into one with a larger combined budget, or deliberately differentiate the audiences enough that they're not quietly competing.

This is one of the cheapest fixes available in an account audit, because it requires no new creative, no new targeting research, just checking a tool that's already sitting in the interface, unused, in most accounts that would benefit meaningfully from what it would show them.