The Windows 10 Mobile upgrade is now being made available for some existing Windows 8.1 devices.

"Consistent with our approach to the Windows 10 PC upgrade, we are focused on delivering a high quality experience for our customers," Microsoft stated on its blog.

If you got an existing Windows 8.1 device, check if the upgrade is available for your device by downloading the Windows 10 Upgrade Advisor app from the Windows Store.

Here are some of the Windows 8.1 devices that are upgrade-ready for the Windows 10 Mobile upgrade: Lumia 1520, Lumia 930, Lumia 640, Lumia 640XL, Lumia 730, Lumia 735, Lumia 830, Lumia 532, Lumia 535, Lumia 540, Lumia 635 (1GB RAM), Lumia 636 (1GB RAM ), Lumia 638 (1GB RAM), Lumia 430, Lumia 435, BLU Win HD w510u, BLU Win HD LTE x150q, MCJ Madosma Q50.

The list only includes some of the Windows 8.1 devices and does not include Windows 10 Mobile devices in the Windows 10 Mobile Insider program.

"As Windows 10 delivers significant new innovations, many older devices are not able to successfully upgrade without an impact on the customer experience," Microsoft posted. "Our goal is to only offer the Windows 10 upgrade to devices that we are confident can continue to deliver a good customer experience."

However, the Windows 10 Mobile upgrade availability for some existing Windows Phone 8.1 devices will depend on some factors: device manufacturer, device model, country or region, mobile operator or service provider, hardware limitations, and other factors.

The Verge reported that Windows 10 Mobile has a number of new features. The Microsoft Outlook and Office have been improved greatly compared to the Windows 8.1 version. Also, Cortana is now much more similar to the Windows 10 desktop version.

Twitter also updated its app for Windows 10 Mobile and desktop versions. The update includes an entirely improved user interface for the Windows 10 Mobile.