Following the release on Tuesday of the first developer beta of iOS 9.2, Apple has now seeded a version for pre-registered public beta testers to try out. As is usual for a first beta, testers will need to install a new certificate, meaning that they would have to completely erase and reset the device in order to downgrade back to iOS 9.1 once they install the new beta. The update includes support for Safari View Controller Action Extensions, among other browser improvements.
