Trident

Trident (or MSHTML) was the proprietary rendering engine that powered Internet Explorer. A fork called EdgeHTML replaced Trident in Internet Explorer's successor, Edge (later referred to as "Microsoft Edge Legacy").

Trident is used in Microsoft Edge when 'IE mode' is on, a feature that allows Edge to render web pages using Trident for compatibility with legacy websites. Trident will only receive security updates until 2029 to support usage in IE mode.