The fall release of macOS 10.13 High Sierra was announced on June 5, 2017 at Apple's WWDC event. On September 12, 2017 at Apple's iPhone event, they announced its release to be September 25, 2017. Like OS X El Capitan and OS X Mountain Lion, High Sierra is a refinement-based update having very few new features. High Sierra uses the new Apple File System and includes enhancements to Safari, Photos, and Mail, among other changes.