UIKit is an application development environment and graphical user interface toolkit from Apple Inc. used to build apps for the iOS, iPadOS, and tvOS operating systems. UIKit provides an abstraction layer of iOS, the operating system for the iPhone, iPod Touch, and iPad. UIKit is insipired by the AppKit found in the macOS Cocoa API toolset and, like it, is primarily written in the Objective-C language. UIKit allows the use of hardware and features that are not found in macOS computers and are thus unique to the iOS range of devices. Just like AppKit, UIKit follows a Model–View–Controller (MVC) software architecture. UIKit contains a different set of graphical control elements from AppKit. Tools for developing applications based on UIKit are included in the iOS SDK.

UIKit in relation to other layers

iOS, watchOS, and tvOS technologies can be seen as a set of layers, with UIKit at the highest level and the core operating system / kernel at the bottom. A hierarchical view of the iOS, watchOS, and tvOS technologies can be shown as follows:

Main features

Some of the main features and technologies of UIKit are:

Main frameworks

UIKit provides the key frameworks for developing applications on devices running iOS, and is based atop Foundation Kit. Other frameworks built by Apple that complement AppKit are:

Ports

Microsoft's WinObjC, the GNUstep-based iOS bridge for the Universal Windows Platform, contains working implementations of frameworks such as Foundation, UIKit, and MapKit released under the MIT License. One of the UIKit implementations is based on XAML. Various efforts have tried to bring UIKit to macOS: