Frequency capping

Frequency capping sets a maximum number of times a specific user can be shown the same ad, or the same campaign, within a defined time window, such as three impressions per user per day. It is a control mechanism applied inside programmatic advertising platforms and ad servers, which track each recognized user or device against the cap before deciding whether to serve another impression.

Frequency capping is the practical lever that keeps the frequency side of reach and frequency planning within its intended range: without it, an automated bidding system will happily keep showing the same viewable ad to the users it can reach most cheaply, concentrating delivery rather than spreading it. It is especially important in retargeting, where a narrow audience of past visitors can otherwise be shown the same ad dozens of times in a short period.

Frequency capping matters because ad effectiveness does not increase indefinitely with repetition; beyond some point, additional exposures produce diminishing or even negative returns as audiences experience ad fatigue or find the repetition irritating, which can depress rather than help outcomes like brand lift. Setting the cap requires judgment: too low, and a campaign may not deliver enough repetition to register at all; too high, and budget gets wasted on audience members who have already seen the message plenty of times.