The 1st build of Windows 10 Technical Preview (for developers) for phones was released a couple of days ago.
Here’s a video by Microsoft on what it is all about:
So if you’re a Windows Phone customer, & love to try the latest stuff before anyone else, a Developer or IT Pro who works with Windows Phones, you may join the Windows Insider program & try out this build. You’ll be getting an insider’s view, assures the Windows team.
