The patch, which is available as both an over-the-air update and iTunes download for iOS 9 users, isn’t accompanied by a changelog. Some speculate, though, that that it modifies the way iOS processes universal links, system hooks which allow app developers to associate webpages with sections inside apps. (A mobile link to an article on the Washington Post’s website, for example, opens the article within the native Washington Post app.)
Prior to the update, iOS 9.3 downloaded, updated, and retained local databases of the individual associations and, when you tapped on a URL, sifted through the database for possible in-app matches. But when an app had many associations, iOS 9 would sometimes struggle to process them all. Developers Sergey Roschin and Ben Collier pointed to the Booking.com app as a particularly egregious example: its huge, 2.4MB universal links database contained every URL on the service’s website.
Further investigation by Collier identified another culprit: the Shared Web Credentials Daemon, the iOS process that lets websites and apps to share sign-in information. Data corrupted by large association files caused the process to crash repeatedly, leading to app slowdowns and hangups.
Previously, deleting the apps wasn’t enough to resolve the hangups because iOS 9.3 didn’t include a mechanism to recover from corrupt associations. The only fixes involved switching from Safari to a third-party Web browser, turning off JavaScript through Safari’s advanced settings menu, and by rebooting the device with Airport mode enabled. But Apple says iOS 9.3.1 should resolve any lingering performance issues that resulted from the system’s handling of universal links, and should furthermore prevent future crashes from occurring.
If you’ve got an iPhone 5, iPhone 5s, iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPad Air 2, iPad Pro or iPad mini that’s been misbehaving lately, the new fix is worth a go.
