watchOS

watchOS is the mobile operating system of the Apple Watch, developed by Apple Inc. It is based on the iOS operating system and has many similar features. It was released on April 24, 2015, along with the Apple Watch, the only device that runs watchOS. Its API is called WatchKit.

The home screen is composed of circular application icons, which can be zoomed in and out with the Digital Crown and dragged and launched by touching the display. Watch apps are commonly miniaturized, highly task-specific versions of their iOS counterparts.