With the ad frequency targeting, Google is giving advertisers more control over how many times people see their YouTube ads.
Previously, managing ad frequency on YouTube was only possible when running connected TV campaigns in Google Display & Video 360.
Now target frequency is available to all advertisers running YouTube campaigns.
In a blog post, Google explains how targeting frequency can help advertisers reach their goals without annoying viewers with too many ads:

“It will help advertisers optimize toward more precise reach and frequency, while ensuring that we continue to provide viewers with the right ad experience. Target frequency allows advertisers to choose a frequency of up to four per week, and our systems optimize for maximum unique reach at the desired frequency.”
Increasing ad frequency without disrupting return on profits
There’s always the risk of diminishing returns when you repeatedly show people the same ad.
Eventually, you’ll reach a point where viewers are turned off and the added impressions result in lower sales.

Google recognizes that seeing the same ad frustrates viewers and is wasteful for advertisers.

A study commissioned by Google shows that a TV advertiser’s ROI is reduced by 41% when the frequency exceeds 6+ weekly impressions, which is 46% of served TV impressions.
That’s nearly half the impressions wasted, Google says:
“Nearly half of the linear TV impressions in our study were considered waste, but the same Nielsen study shows that brands can increase their average weekly frequency from one to three on YouTube with consistent ROI.
This is a huge opportunity for marketers to maximize their impact on the same people they’re already reaching today.”
With targeted frequency, Google aims to help advertisers increase impressions without negatively impacting ROI.
Advertisers can choose a target frequency, and Google optimizes for maximum unique reach on target frequency.
In testing, Google says that more than 95% of YouTube target frequency campaigns reach their frequency goals when set according to recommended best practices.
Availability
Target Frequency is available worldwide for all Google Ads advertisers.
To start using an optimized campaign frequency, create a new video campaign to reach your target frequency and then select your desired weekly frequency.