In January 2015, Microsoft announced that a new browser called Project Spartan will be powering all Windows 10 devices, from smartphones to tablets, PCs and more. The idea behind it is to create a new experience that works well for the modern web, and for that the IE team has built a new rendering engine called EdgeHTML.dll, in order to make the Web "just work".

This doesn't mean that Internet Explorer is going away, as the IE team explained in a Q&A session on Twitter. Instead, IE will benefit from the new rendering engine as well, but the only other changes that will come to it moving forward are related to security and high priority bug-fixes.

Both enterprise users and consumers will have access to Internet Explorer, but the main focus will be on making Spartan compatible with the world's top 9000 websites, which account for over 88% of the Web traffic. The IE team will ship the new browser only if its compatibility pass rate will be better than that of Internet Explorer and other major browsers.

This doesn't mean that small websites will be left out. Microsoft engineers involved with Project Spartan are taking a new approach to solve the compatibility problem, and they have identified a number of key issues:

Legacy vs. modern: The IE team realized that using document compatibility modes with the Trident engine in Internet Explorer would sometimes break websites instead of helping to display them correctly, making compatibility very difficult to measure.

The IE team realized that using document compatibility modes with the Trident engine in Internet Explorer would sometimes break websites instead of helping to display them correctly, making compatibility very difficult to measure. Compatibility View Lists: These were used to emulate legacy IE behaviors, but proved very difficult to maintain, and didn't work well beyond the top sites.

These were used to emulate legacy IE behaviors, but proved very difficult to maintain, and didn't work well beyond the top sites. X-UA-Compatiblity: This made it possible for websites to force an older document mode, but they relied on it even for newer versions of Internet Explorer, while they offered the newer code path to other modern browsers, putting them at an unfair advantage.

This made it possible for websites to force an older document mode, but they relied on it even for newer versions of Internet Explorer, while they offered the newer code path to other modern browsers, putting them at an unfair advantage. Standards focus: With Spartan, the main focus is to comply with Web standards, by adding HTML5 features and trying to bridge the gap in interoperability among browsers. New standards include adaptive video streaming with HLS and DASH, better 3D rendering with WebGL, as well as more gaming related things that will be presented at GDC 2015.

The IE team realized that in order to make it easier for web developers to build compatible websites no matter what browser they focused on, they had to make a break from the past, and build a new engine that is free from 20 years of IE legacy code.

The engineers have also investigated the possibility of using WebKit, but it eventually proved to be more time-consuming and sub-optimal for what they had in mind, considering the way the Web is built. And so the Edge rendering engine was born, to give Windows 10 users a Web "that just works". It also carries a new user agent string, which proved to change the experience quite a bit for such a small change, and also uncovered a few issues that were invisible for a long time.

The efforts of the IE team don't stop here, as they are leveraging the power of the Bing engine to assist in the process of tracking and fixing issues by looking at patterns instead of individual websites. With Windows 10, Microsoft is looking to offer an evergreen operating system, and that also means constantly updating Spartan, with over 40 added web standards, and 3000 interoperability bugs squashed at the time of writing this article.

If Internet Explorer is the browser you love to hate, expect Project Spartan to be the browser you truly love, no matter what type of input you are using. Furthermore, recent leaks show Windows Insiders will be able to play with it pretty soon, although there are still some stability issues to be fixed before we get the bits.

Source: IE Blog