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 (rendered by and also known as “Carousel”) 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. Many of the apps are miniaturized, simplified versions of their iOS counterparts.