According to recent leaked builds of Microsoft's upcoming Chromium-based Microsoft Edge, the browser may contain both a Chromium Blink and an Internet Explorer rendering engine. This could be used to add backwards compatibility for sites that were designed for Internet Explorer.

According to a tweet by Windows sleuth WalkingCat, the new Microsoft Edge appears to have dual-engine support that allows you to host an Internet Explorer session in a tab. This could enable users to utilize the Chromium Blink engine for their normal browsing, but also launch a tab that utilizes the Internet Explore engine for backwards compatibility.

Microsoft Edge may have dual engine support, likely for Enterprise Mode — WalkingCat (@h0x0d) March 24, 2019

In Microsoft Edge Insider build version 75.0.109.0 and later, a new experimental flag was added to edge://flags called "Enable IE Integration", which has a description of "Enables hosting Internet Explorer in a tab".

Enable IE Integration flag

When enabled, a new option will appear under the the Edge menu -> More tools called Host in IE tab as illustrated below.

Host in IE tab

While it is assumed that eventually this option will cause a new tab to open that renders the page using the engine behind Internet Explorer, currently it just launches Internet Explorer to the "http://-dualengineadapter=%22c/Users/[username]/AppData/Local/Microsoft/Edge/Application/75.0.111.0/dual_engine_adapter.dll%22%20-dualenginepipe=5380" URL.

Launched Internet Explorer

According to WalkingCat, this feature has an internal name of "Selfhosting AndIE".

and..... IIRC the dual engine feature in Spartan was also called AndIE??? — WalkingCat (@h0x0d) March 26, 2019

As this feature was found in early Edge Insider builds, which have not been officially released yet, it is not surprising that this feature does not work as anticipated.

If more information becomes available, we will update this article.