Benjamin Mayo, writing for 9to5Mac:
Ad blocking extensions have been possible on Safari for Mac for a long time, but plugin architecture for Safari on iOS is much more limited. With iOS 9, Apple has added a special case of extension for ad blockers. Apps can now include ‘content blocker’ extensions that define resources (like images and scripts) for Safari to not load. For the first time, this architecture makes ad blockers a real possibility for iOS developers to make and iOS customers to install and use.
This has been, for me, the most puzzling new feature in iOS 9. Why is Apple doing this? Is the demand for ad blockers on iOS so high to justify the creation of a new extension point in Safari (and tons of questionable ad blockers coming to the App Store)? Could this be related to shady ad networks still finding ways to automatically redirect web views to the App Store?
The most plausible explanation I’m coming up with is that Apple wants to make it easier to develop third-party content filters (not necessarily ad blockers, like curbi) for parental and educational purposes without workarounds (like MDM and VPN certificates), but I’m not sure.