Formerly known as Windows Phone 10 and then Windows 10 for phones, it's bringing some friends (though, some would call them rivals), with Android and iOS app compatibility.
There's going to be an easy way for developers to port over their existing code, and that means more apps running on Windows 10 Mobile devices.
That bodes well for Microsoft's goal of having Windows 10 on one billion devices in two to three years. Also a big help to increasing its Lumia phone sales is the free Windows 10 download for all W8.1 devices.
Every device running Windows Phone 8.1 right now will be updated to Windows 10 in time. According to Microsoft at its MWC 2015 press conference, it will be updating all the devices it can to the new platform and hopes to have it done by the end of the year.
After months of rumors and speculation Windows 10 Mobile has been officially unveiled by Microsoft. Forget Windows Phone 9, in fact forget Windows Phone altogether, because this is supposed to be Windows... on a phone.
This first build is simply a technical preview of Windows 10 Mobile, and as such contains just a sampling of the features we're expecting to eventually see.
As an unfinished build, this Windows 10 Mobile technical preview is liable to be unstable, and Microsoft recommends caution when installing it - maybe on a secondary Windows Phone device rather than your main phone.
To get started, download the Windows Insider app from Microsoft's digital storefront. Oh, and only users with the Lumia 630, Lumia 635, Lumia 636, Lumia 638, Lumia 730 or Lumia 830 will be able to install it for now.
Cut to the chase
- What is it? The next major upgrade for Windows Phone
- When is it out? Later in 2015
- What will it cost? Nothing, it's a free download
Windows 10 Mobile release date
Windows 10 will ship for desktops later in 2015 and there's every chance that the phone version will arrive at around the same time. Unfortunately Microsoft isn't getting any more specific than that at the moment.
Windows 10 Mobile has begun seeding to selected testers now to help developers get their heads around the new platform.
The good news is that when it does fully launch it will be available for a year as a free upgrade to existing Windows devices, including those running Windows Phone 8.1. So if you have a Windows Phone 8.1 handset you should be able to get Windows 10 on it before the year is out.
One OS to rule them all
The key thing to know about Windows 10 Mobile is that while the version running on your handset will be optimised for a smaller screen it's still just considered Windows 10.
So apps and features will look similar on your phone to on your desktop. You get the full versions of Office, Word and PowerPoint and they will look and operate much the same as the desktop versions.
Settings screens will also look and operate in the same manner across devices and apps will be universal, so Photos, Music, Videos and more will be much the same on desktop, phone and tablet and you can switch between Windows devices almost seamlessly.
It's all about unity
Speaking of seamless switching, Windows 10 is designed to be unified between devices, not just with a similar look and universal apps, but by having phone and desktop work together.
So for example if you clear a notification from the Action Centre on your Windows 10 Mobile, it will also disappear on your computer and vice-versa.
You'll also be able to open and edit Microsoft Office documents on all your different devices, as files will be synced in the cloud and a recent docs list will give you quick access.
You'll still get live tiles with Windows 10 Mobile and it doesn't look identical to the desktop version, but it's not far off. A background image will bleed through the translucent tiles, allowing you to personalise the Start screen beyond just changing the colours.
Swipe to the right and you'll get an apps list as before, but now recently installed apps will be shown at the top, so you can more easily find whatever you last downloaded.
There's also a new layout to the settings screen, making it look a lot more like the version found on desktop and tablets. In fact a few leaked screenshots of the Windows 10 Mobile technical preview have emerged, so you can see the settings screen for yourself above, along with Action Center (or whatever it ends up being called this time round).
As you can see there is a wider range of quick settings than on Windows Phone 8 and a different colour scheme, with blue icons.
Keyboard and messaging
The keyboard is getting a bit of a touch-up on Windows 10 Mobile. It's still the Word Flow keyboard from Windows Phone 8.1, but now it can be resized and even moved around the screen, so you can position it perfectly for your device and fingers.
Plus you can look forward to in-line messaging, allowing you to switch between SMS and Skype without switching apps and it's rocking some fancy dictation skills, as it can output symbols rather than writing the word and will even head into your contacts list to check how you spell a person's name when you speak it.
Camera and photos
The new photos app will be one of many universal apps and being universal it also syncs your images across all your Windows 10 devices using OneDrive.
Not only that, it also removes duplicate images, automatically creates albums and automatically enhances your photos by removing red eye and the like.
If you're not using a Lumia phone then you'll also see some big changes to the camera app, as Lumia Camera is becoming the default app on all Windows 10 handsets. It brings with it auto-HDR, 4K video recording, Rich Capture (which can combine images to create one superior photo) and Dynamic Flash, which takes a photo both with and without flash and then lets you adjust the flash level after the fact.
If you're already using a Lumia then you won't have to wait for Windows 10 Mobile to make use of these features, but the new version of Lumia Camera will also be faster both to launch and take photos than the current version.
Big things are happening to Internet Explorer as part of Windows 10. In fact it's going to be replaced with a new name: Microsoft Edge. That's the official name. Previously, it was codenamed Project Spartan.
The biggest addition is that on desktop at least you can now mark up web pages with notes and drawings and then share them with other users, though we're not sure whether this feature will be available on the smartphone version or not.
More to come
That's all we know so far. We can expect to learn more about the Windows 10 platform as a whole over the coming months before its release toward the end of 2015.
- In the meantime take a look at our first hands-on with Windows 10 Mobile.