Though the company had previously raised issues with iOS 14 and that it could impact their advertising, this Wednesday blog detailed exactly how. 

Facebook Audience Network collects data from the user ( Facebook's data) and provides targeted in-app advertisements. Advertisers use a unique device ID number known as the IDFA in order to make advertisements personalized. 

In iOS 14, these tracking IDFA would be made optional and the user can opt if they want their app to track or not. Facebook said they won't collect IDFA information in iOS 14 at all even though it will make a significant dent in their audience network advertising. 

"We know this may severely impact publishers' ability to monetize through Audience Network on iOS 14, and, despite our best efforts, may render Audience Network so ineffective on iOS 14 that it may not make sense to offer it on iOS14 in the future," Facebook said in the blog.

"While it's difficult to quantify the impact to publishers and developers at this point with so many unknowns, in testing we've seen more than a 50% drop in Audience Network publisher revenue when personalization was removed from mobile ad install campaigns," Facebook said. "In reality, the impact to Audience Network on iOS 14 may be much more, so we are working on short-and long-term strategies to support publishers through these changes." 

Facebook said that their advertising policies will be in compliance with iOS 14's and Apple's preconditions but the social network's whole revenue is derived from advertising and around a billion people view at least one Audience Network ad in a month, so the decision is bound to affect Facebook grandly. 

The blog further cleared some changes Facebook would do for iOS 14 and operations for their partners. The new iOS is expected to launch this year.