Frequency Cap vs Reach: What's the Difference?

Reach is the number of unique people who saw an ad at least once within a given period. It measures how many different people a campaign got in front of, regardless of how many times each of them saw it.

A frequency cap is a limit on how many times the same person can be shown the same ad within a set time window - for example, no more than three times per week. It stops a small slice of the audience from seeing an ad dozens of times while the rest of the target audience sees it zero times.

For a fixed budget, reach and frequency work against each other: showing an ad more times to the same people means fewer total unique people see it, and capping frequency protects reach by spreading impressions across more of the audience instead of repeating them on the same few. It also limits ad fatigue and wasted spend on people who've already seen enough of the message to have made up their mind either way. The right cap depends on funnel stage - awareness campaigns can run a low cap to maximise how many new people are reached, while retargeting a warm audience closer to a decision often benefits from a higher cap, since repetition there reinforces a message rather than wasting it.