It's a fork of the underlying MSHTML engine, that adds some new standard support and more importantly throws out the old compatibility modes and other legacy.
It will run in parallel to IE, which is here to stay for enterprise customers.
It's a complete rebuilt engine called EdgeHTML, it's not hosting the old MSHTML engine anymore. IE will still be around as a browser program (with updates) for those who need it (enterprises, etc).
It's not a redesign, it's a completely new browser built clean and based on EdgeHTML.
IE will still be around as a separate browser that can be used in environments it's needed but Spartan/Edge is completely new and the way forward for the mainstream users.
So we set about to create a new engine using IE11’s standards support as a baseline. I watched Justin Rogers, one of our engineers, press “Enter” on the commit that forked the engine—it took almost 45 minutes just to process it (just committing the changes, not building!).
At the risk of getting pedantic... they basically deleted the majority of it.
>> In the coming months, swathes of IE legacy were deleted from the new engine. Gone were document modes. Removed was the subsystem responsible for emulating IE8 layout quirks. VBScript eliminated. Remnants like attachEvent, X-UA-Compatible, currentStyle were all purged from the new engine. The codebase looks little like Trident anymore (far more diverged already than even Blink is from WebKit). What remained was a clean slate.
At this point, they kept basic stuff any rendering engine would do but it's as clean a start as you can get.
supposedly, from what I have heard, it is a new browser with no legacy code base. And possibly that old IE plugins still work (not entirely sure on this last part).
It doesn’t support any old IE plugins, it contains none of the IE/7/8/9/10 codebase, but instead is based on only the newly written parts of IE11, and it supports Firefox and Chrome addons.
Wow. Why aren't they marketing this? Creating a browser from scratch, considering the current state of web technologies is a huge undertaking. I always thought it's just a re-skinned IE with some touch features.
Not sure about IE plugins but it supports the plugin's from Firefox and Chrome[1]. Technical details would be interesting, but migrating would be little frictionless, if anybody want to try the Edge.
It will run in parallel to IE, which is here to stay for enterprise customers.