Microsoft is finally rolling out its Windows 10 Mobile upgrade to existing handsets today. The software giant has been testing a variety of updates over the past few months, and a number of handsets will receive the update starting today. Microsoft is supporting the Lumia 430, Lumia 435, Lumia 532, Lumia 535, Lumia 540, Lumia 635 (1 GB RAM), Lumia 640, Lumia 640 XL, Lumia 735, Lumia 830, and Lumia 930 initially. While the rollout will start today, it will all depend on when carriers make the update available for devices. Microsoft has created a special upgrade advisor app that will let you know if the Windows 10 Mobile update is ready for your handset, and you can download it from the Windows Store.

Windows 10 Mobile includes a number of new features for existing devices. Outlook and Office have been greatly improved over the Windows Phone 8.1 equivalents, and Cortana is now aligned with the desktop Windows 10 version. Most of the bigger changes are related to Windows 10’s universal apps. Twitter just updated its app across desktop and mobile versions of Windows 10 yesterday, and the hope is that more developers will create a single universal app that spans across tablets, PCs, and phones.