In 2016, with the release of macOS 10.12 Sierra, the name was changed from OS X to macOS to streamline it with the branding of Apple's other primary operating systems: iOS, watchOS, and tvOS. macOS 10.12 Sierra's main features are the introduction of Siri to macOS, Optimized Storage, improvements to included applications, and greater integration with Apple's iPhone and Apple Watch. The Apple File System (APFS) was announced at Apple's annual Worldwide Developers Conference (WWDC) in June 2016 as a replacement for HFS+, a highly criticized file system.