Facebook sent a note to app developers on Wednesday explaining how Apple’s privacy changes integrated into its newest operating system will hinder the company’s ability to serve targeted ads to iPhone users while they use outside apps.

The changes will affect Facebook’s Audience Network business, the company wrote in the letter. The network connects users’ identities with their off-platform activities. That enables the company to serve users ads on apps outside of Facebook.

The company wrote that some might still see ads from Facebook, but they will be less relevant. Apple’s changes to its operating system may “render Audience Network so ineffective on iOS14 that it may not make sense to offer it on iOS14 in the future.”

The changes take effect in Apple’s new operating system for iPhone, the iOS14. It was released in beta to developers this week.

Facebook, in the note, explained that the changes would likely result in reduced earnings for developers.

Earlier this week Google said it plans to release a default setting to block advertisements by the end of August that violate what it considers heavy ad intervention. Those policies should occur with Tuesday’s release of Chrome 85.

Google in May published a blog defining “heavy ads” as those that consume more than 4MB of network data or 60 seconds of total CPU use, both drain battery life. Only 0.30% of ads meet these criteria, but they make up 27% of total ad network data consumption and 28.00% CPU use.