Microsoft's upcoming Windows 10 upgrade, with unified experience to users across all platforms such as mobiles, tablets and PCs, will be available for all Lumia devices running on Windows Phone 8.

The preview build of Windows 10 was released on September 30 and the OS is touted to be the next major version for Windows Phones. There is no information about the date when the update will be available.

While announcing the launch of Windows 10, the software giant had stated that in early 2015 it will introduce the consumer chapter and talk about other device types and consumer features.

Then, the company would continue its conversation with the developer chapter at its Build conference, and later in the year it will release Windows 10 and look forward to some new devices.

Meanwhile, an announcement was made via an official Lumia tweet. The posting notes that Microsoft will launch new Windows 10 models as well.

Recently a new Lumia device with Microsoft branding appeared via a leak. Dubbed as Microsoft Lumia 940, the smartphone is expected to run on Windows 10 OS according to the leaked spec sheet, which could be the first smartphone to boast the latest Windows OS, reports PhoneArena.

Besides, earlier this month ex-Microsoft employee, Nawzil shared a few new Windows Phone builds; Windows Phone 8.1 Update 1 with build 8.10.14200 and Windows Phone 8.1 Update 2 with build 8.10.15xxx. Along with these there is mention of Windows 10 with build version, which is currently being tested.