Last year, we committed to the principle that the mobile web should just work for everyone, and introduced hundreds of targeted improvements to Internet Explorer in the Windows Phone 8.1 Update to dramatically improve interoperability with the mobile web. In November, we revealed the new rendering engine for Internet Explorer and Project Spartan on Windows 10, built on the same successful interoperability principles. Today, we’re excited to bring this new rendering engine to phones for the first time with the Windows 10 Technical Preview for phones.

In today’s preview build, the new rendering engine is hosted within Internet Explorer. Project Spartan, powered by the same new engine, will replace Internet Explorer on phones in a later preview.

What’s new in the Technical Preview for phones

For multiple releases, we’ve been committed to shipping a unified web platform for Windows devices across all form factors and screen sizes. As a result, the new Windows 10 web platform on phones comes with the same interoperability improvements, new features, increased performance, and improved standards support we’ve beenpreviewing on PCs for the last several months. Going forward, you can expect to see an even tighter coordination of new web platform update availability on PCs and phones.

Windows 10 introduces a new user agent string for phones– based on our new desktop user agent string– designed to get the most modern, interoperable content for the mobile web. Sites inspecting the user agent string for analytics should be aware of the new string, but we continue to believe that feature detection rather than browser detection is the best solution for web developers writing interoperable content.

Mobile web and apps interoperable by default

The new rendering engine will be used for all web pages loaded in the browser on Windows 10 phones. Like on PCs, “x-ua-compatible” tags will no longer be supported to force older compatibility document modes. This ensures that sites on the mobile web will always get the latest, most interoperable engine.

Starting in Windows 10, Universal Apps powered by the new rendering engine will always use the latest update to the engine installed on the device. For application compatibility, Windows Phone 8.1 and earlier apps powered by WebBrowser or WebView controls will continue to be powered by the appropriate version of Trident.

Try it out and share your feedback

You can download the Windows 10 Technical Preview for phones today via the Windows Insider program, and share feedback directly with our engineering teams using the Windows Feedback app included in the preview. We also welcome feature requests and developer feedback via the Internet Explorer Platform Suggestion Box on UserVoice, @IEDevChat on Twitter, and in the comments below. We’re eager to hear your feedback and use it to make the mobile web a better experience for customers and developers alike!

— Kyle Pflug, Program Manager, Internet Explorer