Trident

Trident (also known as MSHTML) is the name of the layout engine for the Microsoft Windows version of Internet Explorer.

It was first introduced with the release of Internet Explorer version 4.0 in October 1997; it has been steadily upgraded and remains in use today. For versions 7 and 8 of Internet Explorer, Microsoft made significant changes to the Trident layout engine to improve compliance with web standards and add support for new technologies. With version 5.0 of Trident, Microsoft intends to comply with many modern web standards, and also intends to significantly update the layout engine to be more competitive and modern compared to other current layout engines.

Trident was designed as a software component to allow software developers to easily add web browsing functionality to their own applications. It presents a COM interface for accessing and editing web pages in any COM-supported environment, like C++ and .NET. For instance, a web browser control can be added to a C++ program and Trident can then be used to access the page currently displayed in the web browser and retrieve element values. Events from the web browser control can also be captured. Trident functionality becomes available by linking the file  to the software project.

All versions of Internet Explorer for Windows from 4.0 onwards use Trident, and it is also used by various other web browsers and software components. In Windows 98, Windows Me, and Windows 2000, it is also used for the Windows file manager/shell, Windows Explorer. The Add/Remove Programs tool in Windows 2000 and Windows XP uses Trident to render the list of installed programs and in Windows XP, it is also used for the User Accounts Control Panel, which is an HTML Application. Trident however was not used by the Internet Explorer for Mac (which uses Tasman), nor by the early versions of Internet Explorer Mobile.