Microsoft has finally begun the rollout of Windows 10 Mobile to select Windows Phone 8.1 devices.

You can download an app to see if the upgrade is available for you device, which we discuss below. Microsoft said the first phones getting the upgrade include a "limited set of Windows Phone 8.1 devices and does not include some devices that are currently running Windows 10 Mobile in the Windows 10 Mobile Insider program." It also said many older devices can't upgrade.

To help you figure out if your phone is eligible to upgrade, as well as which app you can download to check for the update, we've detailed all you need to know. Also, be sure to check out Pocket-lint's review of the mobile operating system, where we described the software as something of a mixed result. It's a more rich platform than Windows Phone 8.1, with new options in the mix.

There's more integration, such as Skype, and better handling with Outlook and individual Office apps, for a smartphone experience that feels more mature. But we were not taken with the design.

Windows 10 Mobile is Microsoft's new mobile operating system. It's a successor to Windows Phone 8.1 but is an edition of Windows 10, Microsoft's operating system for personal computers. The idea is that Windows 10 will unify Microsoft's platforms into a single, converged operating system.

According to Microsoft, the following phones and devices can upgrade to Windows 10 Mobile: Lumia 1520, Lumia 930, Lumia 640, Lumia 640XL, Lumia 730, Lumia 735, Lumia 830, Lumia 532, Lumia 535, Lumia 540, Lumia 635 (1GB), Lumia 636 (1GB), Lumia 638 (1GB), Lumia 430, Lumia 435, BLU Win HD w510u, BLU Win HD LTE x150q, and MCJ Madosma Q501.

However, according to The Verge, Microsoft is initially supporting the following phones: Lumia 430, Lumia 435, Lumia 532, Lumia 535, Lumia 540, Lumia 635 (1GB), Lumia 640, Lumia 640 XL, Lumia 735, Lumia 830, and Lumia 930.

To get Windows 10 Mobile, you need to manually initiate the update.

Microsoft has created an Upgrade Advisor app that will let you know if the Windows 10 Mobile update is ready for your phone. You can download the app from the Windows Store. Although this is how the rollout is kicking off, Venture Beat claimed Microsoft will one day actively push the update to eligible devices. The rollout of course depends on when carriers make the update available.

Go to Pocket-lint's Windows 10 Mobile hub for related news, reviews, and analysis, or you can read Microsoft's announcement.