Frequency Capping.

Two metrics belong together: reach counts how many different people have seen an ad, frequency how often each of them has seen it on average. Impressions are reach multiplied by frequency. Without a limit, ad systems tend to show ads again and again to the same people who are deemed most promising. Beyond a certain point, each additional impression achieves less, and some people start to feel irritated by the brand.

Frequency capping matters most in retargeting. The audience there is small, for example visitors from the past few weeks, and the budget is spread across few people. Without a cap, a website visitor sees the same ad on every other page. For reach campaigns billed on a cost per thousand impressions basis it is also worth watching frequency, because impressions rather than clicks are the goal.

Where and how frequency can be controlled depends on the platform and campaign type. In Google Ads, frequency settings exist mainly for display and video campaigns; for highly automated campaign types, Google largely controls delivery itself. With Meta Ads, a frequency cap can be set for the reach objective among others, and average frequency is visible in reporting. With LinkedIn Ads, the options are more limited depending on the format. Which options are currently available changes and should be checked in the relevant account.

The cap is never entirely exact. Platforms count per account, browser or device; someone who browses on phone and laptop or declines cookies may be counted more than once. There is no single figure that is right for every business. It makes more sense to watch frequency together with click rate, cost per enquiry and negative feedback: if the click rate falls noticeably while frequency rises, the ad has run its course for that audience. A tighter cap, new creatives or a larger audience will then help.