The ad limits per Page on Facebook will be based on the ad spends, higher the ad spends, the more number of ads will be allowed per Page.
Facebook has categorized the advertiser size into four tiers, the Page's highest spending month in the last 12 months will be considered to decide the ad limits per page.
The ad limits will be enforcement will roll out from February 2021 through Summer 2021. There are mainly two factors that have led to this change and the launch of ad limits per page on Facebook.
Factors
Learning Phase
Every ad shown goes through a learning phase, wherein Facebook's ad delivery system learns more about the right places and the right people to show the ad to.
The more an ad is shown, the more the delivery system learns about it and gets better at optimizing the ad's performance.
This period called the learning phase is an experiment for the delivery system to explore the best way to deliver an ad set.
When an advertiser runs a higher number of ads at once, the lesser number of ads exit the learning phase. Consequently, the ads that did not pass through this phase do not get their performance-optimized.
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Machine Learning driven products
By introducing ad limits, Facebook is also making a push for its machine-learning driven products for personalizing ads.
Several advertisers would previously test a higher number of ads with different formats and various personalizations, since this option would not be available, Facebook is also promoting the use of its ad products.
The ad products being Dynamic ads or more such as Dynamic Formats and Ad Creative.
Dynamic ads promote your inventory who have previously shown interest on your website, app, or anywhere on the internet. The product can also retarget people who have previously taken any action on the app or website.
Dynamic formats and ad creative show people different formats such as carousel or collection, description variations, and more. This ad product basically tries diverse packaging for an ad to show users what they're most likely to respond to.
Advertisers can see when the ad limit will go into effect for their Page in Ads Manager. Developer resources can be found here, with additional enforcement details in the Help Center.