Microsoft is putting Project Spartan front and center in Windows 10, with the new browser pinned to both the Start menu and the Windows task bar. You'll still be able to find IE, and if you've already pinned it, then it won't be removed. Microsoft recently announced that IE and Project Spartan would have separate rendering engines, and the change has now made its way to Windows with the Edge engine removed from IE in Windows 10 Build 10049. The old IE will remain part of Windows 10 (if only visible from All Apps) for businesses to use with legacy apps.
Web developers will find this build of Windows 10 to be useful for tuning sites and applications in preparation for Windows 10. You won't find any surprising new HTML or CSS features in this release. Project Spartan is based on the same version of the Edge engine used by IE in build 10041 with some minor additions, among them support for responsive images.
But as in IE of the previous build, there's support for much of ECMAScript 6, as well as Web Audio, CSS Gradient Midpoints, CSS Conditional Rules, and Touch Events. Now that Microsoft has divorced its new rendering engine from IE's Trident, Project Spartan will be where you'll find new Web technologies in the future, making it important to add the Windows 10 Technical Preview to Web test suites.
With only a week or so of development time separating this Windows 10 release from build 10041, Project Spartan is not merely the big news but the only news in this release. Apart from the new browser, there are only a handful of bug fixes in build 10049. Still, it's another step on the road to Windows 10's promised summer release.
Remember: This is still an early beta release of Project Spartan. On the HTML5Test, Project Spartan beats Internet Explorer 11 (375 to 336) but still lags the latest versions of Chrome (518), Opera (497), Firefox (449), and Safari (396). Much remains to be revealed before Windows 10 launches, including — one hopes — improved compatibility with HTML5.
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