Frequency capping is a setting in an ad serving platform that controls how many times an individual user should see a specific advertising creative. Advertisers typically want to cap the number of times a certain ad or creative is seen in order to control budget or to limit ad fatigue for a user.

Ad fatigue is the idea that showing the same ad to a user many times may create a negative user experience or incite negative sentiment toward the brand or product advertised.

How does frequency capping work?

Ad serving platforms must identify unique users in order to apply frequency capping. Without an understanding of individual users, there will be no entity to which an ad server can apply a frequency cap.

The method of identifying a unique user depends on the platform the ads are served on.

Web

Cookies are the primary method to identify individual users on the web. When an ad server displays an advertisement they will drop a cookie on a user's browser that will allow them to identify that user the next time they encounter them. This cookie is a small text file that contains an identifier unique to that user.

Things become a little more complicated in programmatic advertising. Since DSPs do not have direct access to a user's browser, they rely on the SSP to inform them if it is a known user. This process is called "Cookie Syncing" and you can learn more about it in this post.

Mobile

Thanks to forethought by Apple and Google, frequency capping on mobile is more straightforward. These companies created "advertising identifiers" that are unique to a user's device. Apps can access these identifiers and pass them to their ad server to identify a unique user. These identifiers are:

  • IDFA (iOS)
  • AAID (Android)

Connected TV

Similar to mobile, some CTV platforms have their own advertising identifiers that can serve as markers for unique users. These CTV advertising identifiers are:

  • RIDA (Roku)
  • AFAI (Amazon Fire)
  • TIFA (Samsung)
  • AAID (Android TV)
  • IDFA (Apple TV)

These identifiers can also be used for audience targeting, which we explored in this post.

Once an ad serving platform has an understanding of unique users, they simply have to log the number of impressions served to each user for a given creative.

Frequency Cap Options

There are only two inputs required to set a frequency cap: how many times should a unique user see this ad and in what time frame? Time frames can vary from an hour all the way to the lifetime of a user.

Frequency caps can sometimes be abbreviated in insertion orders or when discussing with someone. For example, someone may say they need a "3x24" frequency cap, which simply means 3 views per 24 hours. This means a user should only be able to view a creative three times in a single day.

Identifying unique users will become more challenging with the demise of third-party cookies, and may soon rely on user logins and publisher-provided identifiers. Apple is also becoming more restrictive over the use of its advertising identifiers, although the IDFV may be a viable alternative to power frequency capping.

Despite the ongoing push for user privacy, users will appreciate any efforts to limit the number of times they have to see the same ad over and over again.