Microsoft is building a new browser as part of its Windows 10 push

There's been talk for a while that Microsoft was
going to make some big changes to Internet Explorer in the Windows 10
time frame, making IE "Spartan" look and feel more like Chrome and Firefox.

It
turns out that what's actually happening is Microsoft is building a new
browser, codenamed Spartan, which is not IE 12 -- at least according to
a couple of sources of mine. Thomas Nigro, a Microsoft Student
Partner lead and developer of the modern version of VLC, mentioned on
Twitter earlier this month that he heard Microsoft was building a brand-new browser. Nigro said he heard talk of this during a December episode of the LiveTile podcast.

Spartan is still going to use Microsoft's Chakra JavaScript engine
and Microsoft's Trident rendering engine (not WebKit), sources say. As
Neowin's Brad Sams reported back in September, the coming browser will look and feel more like Chrome and Firefox and will support extensions. Sams also reported on December 29 that Microsoft has two different versions of Trident in the works, which also seemingly supports the claim that the company has two different Trident-based browsers.

However, if my sources are right, Spartan is not IE 12. Instead, Spartan is a new, light-weight browser Microsoft is building.

Windows
10 (at least the desktop version) will ship with both Spartan and IE
11, my sources say. IE 11 will be there for backward-compatibility's
sake. Spartan will be available for both desktop and mobile
(phone/tablet) versions of Windows 10, sources say.

Spartan is
just a codename at this point. My sources don't know what Microsoft
plans to call this new browser when it debuts. The IE team hinted during
a Reddit Ask Me Anything earlier this year that the team had contemplated changing the name of IE
to try to get users to realize the much more standards-compliant IE of
today is very different from older, proprietary versions of IE.

Microsoft may show off Spartan on January 21 when the company reveals its next set of Windows 10 features.
But my sources also aren't sure if Spartan will be functional enough
for inclusion in the Windows 10 January Technical Preview and mobile
preview builds that are expected to be available to testers in early
2015. It may not show up in the test builds until some point later, they
say.

Will Microsoft end up porting the Spartan browser to
Android, iOS and/or any other non-Windows operating systems? I'm not
sure. The IE team said a few months back that Microsoft had no plans to port IE to any non-Windows operating systems.
But Spartan isn't IE. And these days, Microsoft is porting much of its
software and services to non-Windows variants. So I'd say there's a
chance that this could happen somewhere down the line ....

 | ZDNet