EdgeHTML is a proprietary browser engine from Microsoft that was used in Microsoft Edge Legacy, which debuted in 2015 as part of Windows 10.
EdgeHTML is a fork of the MSHTML (Trident) engine of Internet Explorer. It is designed as a software component that enables developers easily to add web browsing functionality to other apps.
In 2018, Microsoft began rebuilding Edge as a Chromium-based browser, which meant that EdgeHTML would no longer be used in the Edge browser. This transition was completed in April 2021. Past this date, EdgeHTML does, however, continue to be supported and used in Universal Windows Platform apps.