What Microsoft browser engine powered legacy Microsoft Edge?

Legacy Microsoft Edge used Microsoft’s EdgeHTML browser engine.

EdgeHTML was introduced with the first Microsoft Edge release in Windows 10 in 2015. It was derived from the older Trident engine but represented a substantial cleanup and modernization: Microsoft removed many Internet Explorer-only technologies, including ActiveX support and legacy document modes, while focusing on current web standards and interoperability.

EdgeHTML was a “living” engine, meaning Microsoft intended to update it continuously rather than treat it as a fixed compatibility layer. It powered the original Edge on Windows 10, commonly called Microsoft Edge Legacy after the later browser arrived. EdgeHTML was therefore separate from both Internet Explorer’s Trident and the Chromium-based Edge engine used today.

Microsoft eventually abandoned EdgeHTML when it rebuilt Edge around Chromium. The original Edge Legacy desktop application reached end of support in March 2021, completing the transition away from Microsoft’s in-house engine for the main browser.