Frequency Capping is a method in online advertising to limit the number of times a banner ad is shown to a single user.

Some ad servers may also refer to this as impression capping.

One of the best arguments to set such a cap is to minimize banner blindness and to increase the CTR and ROI of your campaigns. Frequency capping allows you to reduce campaign costs while increasing your campaign's unique reach.

If you're on the buy side, this is once more an excellent example why you need an ad server for advertisers. To get the maximum out of your advertising budget, you need to be in control.

Frequency Caps: Best Practices

Setting a frequency cap for online advertising campaigns is almost always recommended in most situations, unless you're running remarketing or brand awareness campaigns (where CTR is not your KPI).

If you're a publisher, limiting the frequency rate is recommended to avoid 'stalking' your visitors with the same ad over and over again. The optimal ad frequency is hard to determine and may depend on the type of campaign, your objective and the available inventory. We believe it's best practice to:

• Set an initial cap between 5-7 impressions per day
• Gradually increase this frequency while measuring your your KPI's performance (usually CTR)
• Enable Lazy-Loading of your ads for better viewability and increased CTR

Finding the Optimal Ad Frequency

Is there an optimal frequency cap? Fine-tuning your cap to find an optimum might be easier said than done: you don't want users to be bombarded with the same ad all the time, while at the other hand you want to make sure your audience gets the message.

You can set up a simple test to see what works in your situation. Start with an impression cap of 1 impression per 24 hours per user and measure your CTR over that day. Gradually increase your cap and keep measuring CTR, until you end up with a table like this:

In the example above, you're actually trading impression volume for a higher CTR and a higher unique reach.

What about setting multiple frequency caps?

A common strategy to distribute media exposure over the day is to set multiple impression caps. This can be a clever method to make sure that visitors who stay on the page for a while are 'remembered' about your message every now and then.

For example, you may want to configure your campaign to have the following caps:

• 5 impressions per hour
• 25 impressions per day

Such an approach will show the ad during 5 hours, while avoiding wasting your budget.

Frequency Capping under the GDPR and CCPA

Traditionally, frequency caps work by generating a unique ID which is stored in a third-party cookie. This ID is send along with every ad request. The ad server keeps an internal log by matching the unique ID with the number of times a certain ad was shown.

This practice however is illegal under the GDPR as per May 2018, since a unique identifier is considered Personal Identifiable Information (PII). Publishers and advertisers who are still using old cookie-based ad servers may expect heavy fines for non-compliancy.

As a solution, the technology behind frequency capping should not be based on PII, or on completely anonymized data as used in machine learning.

By not processing personal data, this approach is GDPR and CCPA compliant.

Use Machine Learning in 2024 (and forget about caps)

We're in the year 2024 and machine learning algorithms are everywhere. They are great to calculate the expected click-through rate of a given user based on the day of the week, location, browser, language and the number of times the ad has already shown to that user.

Imagine that people from the west need to see an ad 3 times before they click, while people from the east need to see the same ad 8 times before they click. In this example, a one-size-fits-all approach doesn't work... With machine learning, your frequency cap will be optimized automatically for each individual user.

Automatically improve CTR with Machine Learning in AdGlare

In Summary

Frequency caps comes with great advantages for both advertisers and publishers. You'll likely benefit from capped campaigns because it...