WebKit is a browser engine developed by Apple and primarily used in its Safari web browser, as well as all web browsers on iOS and iPadOS. It is also used by other devices and operating systems such as PlayStation consoles, Tizen mobile operating systems, Amazon Kindle e-book reader, and Nintendo consoles. WebKit started as a fork of the KHTML and KJS libraries from KDE, and has since been further developed by KDE contributors, Apple, Google, Nokia, Bitstream, BlackBerry, Sony, Igalia, and others.

Web developers can use WebKit to render HTML and run JavaScript in the Adobe Integrated Runtime application platform. The CSS -webkit-appearance property allows web developers to make HTML components look more like native User Interface (UI) controls. WebKit also supports the CSS -webkit-appearance property, which is a proprietary CSS extension. The -webkit prefix on WebKit extensions denotes that they are part of the WebKit open-source framework.

Applications based on WebKit or Blink, such as Safari and Chrome, support a number of special WebKit extensions to CSS. These extensions are generally prefixed with -webkit- . Some of the -webkit- prefixed CSS properties include -webkit-transform, -webkit-transform-origin, -webkit-transform-style, -webkit-transition, -webkit-transition-delay, -webkit-transition-duration, -webkit-transition-property, and -webkit-transition-timing-function.

In summary, WebKit is a browser engine developed by Apple and used in Safari and other web browsers on iOS and iPadOS. It is also used by other devices and operating systems. Web developers can use WebKit to render HTML and run JavaScript in the Adobe Integrated Runtime application platform. WebKit also supports the CSS -webkit-appearance property and other -webkit- prefixed CSS properties.