Apple unveiled its latest mobile platform iOS 9 amid much fanfair at the WWDC event on Monday. While the company touted many new features in the operating system, it avoided publicly announcing that the iOS 9 version of Safari will allow developers to create extensions that blocks ads. The ‘Content Blocking’ feature was buried in the developer documents for the software.

iOS 9 Ad Blockers

Ad blocker available in iOS 9 beta builds

Content Blocker is now available in iOS 9 beta builds. Menu option for the feature explains that it will “affect what content is loaded while using Safari.” It will allow developers to pass a set of rules that can be used to block content such as images, cookies, popups, resources and other elements, according to Apple’s developer page.

In the past few years, ad-blockers have become a controversial issue. As many as 140 million people were blocking ads on their devices at the end of 2014. Ad-blocker is a browser plugin that removes all the flashy, data-consuming ads from every webpage. The iOS 9 is expected to arrive this fall with the next-gen iPhone.

Why did Apple add content blocking in iOS 9?

Ads pay the bills to keep millions of websites worldwide operational. It’s still unclear why Apple could be encouraging ad blocking. This feature will prevent ad networks from tracking your every online move so that they can serve relevant ads. Apple has its own advertising network called iAd. The new feature may be Apple’s strategy to push websites relying on ad revenue into building native apps, says Owen Williams of The Verge. This way, the iPhone maker could take a percentage of the ad revenue and ensure that the ads still appear.

One thing is clear: ad blocking feature in iOS 9 could be a serious blow to mobile advertisers as well as giants like Google and Facebook, whose primary source of revenue remains advertising.