Microsoft Releases Phone-based Windows 10 Technical Preview

Microsoft today released a limited Windows 10 technical preview or smartphones, only available on six select Lumia devices.

Users of the Lumia 630, 635, 636, 638, 730 and 830 are now able to access the technical preview via the Windows Insider program, according to a blog post by Gabriel Aul, a data and fundamentals team lead for Microsoft's Operating Systems Group. The majority of carriers are said to be supported, with the exception of those in China. Microsoft plans to expand access to the technical preview in future builds, Aul said.

"[F]or this technical preview, we need to start with a small subset of devices in order to isolate OS issues from hardware or board support package issues so we can stabilize the platform," Aul wrote. "Support for more phones will be phased in with each new build, and we'll announce which devices are being added when the build comes out. Expect the list to grow slowly at first but expand comprehensively over time."

In a video (see below), Joe Belfiore, corporate vice president of Microsoft's Operating Systems Group, gives a demonstration of new features in Windows 10 for phones. Improvements include an expanded Action Center, more customization options for the Start Screen, easier access to recently installed apps and more intuitive speech-to-text transcription.

Belfiore also showed how touch-enabled Office apps will eventually work on Windows 10. However, those Office apps are not available in this technical preview build. While preview versions of Office apps for Windows 10 have been available since last week, they currently work only on PCs and larger tablets running the Windows 10 technical preview. The final version of Windows 10 for phones will include the Office apps at no extra cost.

Users of the technical preview will also encounter a more stripped-down version of the Cortana voice-activated assistant, Aul said. For this technical preview, Cortana only supports English and is available only to users in the United States. In addition, it lacks some features that are enabled in Windows Phone 8.1, though Aul did not specify what those missing features are.

Also missing from the technical preview is the new Spartan browser, which uses the EdgeHTML rendering engine. The technical preview instead uses Internet Explorer as its default browser, but as Microsoft explained in a separate blog post on Thursday, that will change in future builds: "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."

Aul's blog listed a number of known bugs with the technical preview. He acknowledged that Windows 10's first public outing on phones may be disappointing for some users, given the number of issues and missing features, but said that Microsoft's focus with this build has been on "platform development rather than the completeness of the UI."

"This preview is still very much under development and you're going to see some rough edges," he wrote. "You will encounter bugs. You will see experiences that are clearly just not done yet, and UX that lacks polish at this point. DON'T WORRY! It will improve as we go and new features, stability and performance improvements, and more polished UX will come at each step."

As a safety measure, the Windows 10 technical preview for phones comes with a Windows Phone Recovery Tool that would enable testers to roll back their devices to the previous OS version if necessary.

Aul also gave an explanation for why Microsoft is initially excluding higher-end Lumia phones from this first technical preview build:

Some context on why we chose these and not higher end phones like the 930/Icon or 1520: We have a feature that will be coming soon called "partition stitching" which will allow us to adjust the OS partition dynamically to create room for the install process to be able to update the OS in-place. Until this comes in, we needed devices which were configured by mobile operators with sufficiently sized OS partitions to allow the in-place upgrade, and many of the bigger phones have very tight OS partitions.

About the Author

Gladys Rama is the senior site producer for, and


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