This engine is closed-source, but Microsoft has exposed an application programming interface (API) that permits the developers to instantiate either MSHTML or a full-fledged chromeless Internet Explorer (known as the WebBrowser control) within the graphical user interface of their software.
Actively maintained: Discontinued: Other applications that are not primarily for web browsing, such as Intuit's Quicken and QuickBooks, AOL, Winamp, and RealPlayer, use the rendering engine to provide a limited-functionality "mini" browser within their own user interfaces.
On Windows, components of Internet Explorer are also used in Windows Explorer, the operating system shell that provides the default file system browsing and desktop services.
This integration is an often-exploited "back door", since the Internet Explorer components make available more of the functionality within the HTML code.
They run with HTML Application Host, which is a plain Internet Explorer shell without any GUI elements around it.