Microsoft's October 2019 hardware event was full of surprises. The Surface Pro 7 and Surface Laptop 3 were joined by the Surface Pro X, a brand new device with the company's own processor inside.

However, arguably the most exciting new products were the Surface Duo and Surface Neo, two foldable dual-screen devices. While the Duo will come running Android, the Neo will ship with a modified version of Windows known as Windows 10X. 

We heard precious little about this new operating system until February 2020, when Microsoft revealed much more about how it might run on this new form factor. Crucially, this included how it will support older so-called 'Win32' apps.

So what is Windows 10X exactly?

It’s a new version of Windows designed specifically for dual-screen devices, though it will run on single-screen ones as well.

It isn't Windows 10, even though it sounds - and looks - just like a new version of that operating system.

It's confusing because Windows 10 supports dual screens already, but as you'll see, Windows 10 isn’t really suitable for the sort of small-screened, portable devices we’re talking about here. They are the next-generation of mobile PCs, designed to be used alongside your existing desktop one.

When will Windows 10X be available?

Initially, Windows 10X was expected to debut on Microsoft's own Surface Neo towards the end of 2020, before making its way to third party manufacturers soon after. 

However, in response to product delays brought about by the coronavirus pandemic, the software will be available much sooner for laptop and PC users. 

An official blog post announced Microsoft's intention to roll out Windows 10X to single-screen devices initially, ahead of its arrival on the Surface Neo and other dual-screen PCs. This news will inevitably push their release back to 2021. 

What's new on Windows 10X?

A new user interface

The Surface Neo is one of these new devices. It has two 9in screens, so it’s a bit like two tablets tablets joined with a hinge. Except that it’s way more than that.

Along with a stylus, you can use a magnetic keyboard with the Neo. It can sit on top of one of the screens, leaving a strip that’s about a quarter of the display visible. Microsoft calls this the Wonder Bar, the reason being that it can show a mini version of an app, an emoji panel, as well as reserving an area that you can use as a track pad to control a mouse pointer.

What is Windows 10x?
Image: Microsoft

When both screens are visible, you can choose to run a different app on each one (a web browser and Word, say) or make a single app spread across both screens in an intelligent way that isn’t just zooming to fill the space.

Rotate it from landscape to portrait, flip it to tent mode for desk use (where the hinge is at the top and you can see just one screen or attach the keyboard and apps will automatically rearrange themselves to suit, and the interface adjusts itself for touch- or keyboard/pen input.

What is Windows 10x?
Image: Microsoft

A new Start menu

Windows 10X also has a new Start menu which looks a bit like a search engine home page: a search bar at the top, links to apps below and your recently accessed documents and web pages below that. Here it is stretched across the two screens of the Lenovo ThinkPad X1 Fold:

What is Windows 10x?

Five different 'postures'

As you might imagine, developers need to optimise their apps so they play nicely in Windows 10X, and that’s one of the main reasons why Microsoft was so keen to show off the Neo 12 months before its launch.

Windows 10X devices can be used in five different modes, so apps need to work no matter which one the user has picked:

What is Windows 10x?

On 11 February 2020, developers got access to a Windows 10X emulator so they can see how their apps will behave in the OS, and optimise them without having an actual 10X device in their hands.

 What is Windows 10x?

The announcement of the development kit also highlights that the new Edge browser – based on the some Chromium platform as Google’s Chrome – will be an integral part of Windows 10X and has been built with dual-screen support in mind.

All of the above is why a new, different version of Windows is required, and why Windows 10X isn’t going to be an upgrade for Windows 10 users.

You might know that there are already lots of different versions of Windows 10: it runs on laptops, PCs, tablets (such as the Surface Pro 7), the Xbox One, Internet of Things devices and the Hololens headset.

However, while all of those share some code between them (known as One Core), there is a new, stripped-down operating system on which Windows 10X is built.

Although Microsoft hasn’t said it officially, this is called Windows Core OS, and there’s still plenty unknown about it.

You don't need antivirus on Windows 10X

The operating system is 'read-only' to apps, which means any malware cannot wreak havoc with system files.

If that sounds familiar, it's because that's how Windows 10S worked. But no-one liked it because you could only run apps installed from the Microsoft Store. And there weren't a whole lot to choose between. 

Windows 10X does things differently because it will allow you to install 'trusted' apps - by using signed code and apps with a good reputation - from any source, including a web browser, a USB stick or something else.

Can Windows 10X run older Windows apps?

Yes. Unlike Windows 10 S - and also the newer Surface Pro X, which uses an ARM-based processor - devices that run Windows 10X will have an Intel processor and use a ‘container’ to run legacy Windows programs. 

A container is a bit like a fenced-off area (or sandbox) where apps only have access to the resources that the user has granted and, as mentioned, no write-access to the operating system. 

In the case of Win32 apps, which is any app that isn’t from the Microsoft Store or an app that runs entirely in a web browser (web apps such as Gmail, for example), they are run in a "guest" operating system, and are given access to the screens, keyboard and mouse via a high-performance remote-desktop protocol.

In simpler terms, it means that older apps aren't supported natively and have to be run in a virtual 'Old Windows' operating system. And if you've ever used the built-in Windows remote desktop tool to control one computer from another, that's basically how you'll access Win32 apps on a device running Windows 10X.

Let's hope that this method doesn't cause them to run too slowly.

There are a couple of reasons why Win32 apps can't run natively. First, because Windows Core OS doesn't support them, and second because they’re not necessarily written to be efficient with battery power. Mobile, dual-screen devices such as the Neo are very thin, which doesn’t leave much room for a huge battery.

This does mean that running a lot of virtualised Win32 apps could drain the battery faster...

Updates will take 90 seconds

Unlike Windows 10, Windows 10X will work more like Android and Chrome OS (the operating system on Chromebooks). This allows it to download and install feature updates in under 90 seconds, Microsoft says.

And that is much more in keeping with what everyone expects from modern mobile devices.

Which devices will run Windows 10X?

There’s the Surface Neo for one, but Microsoft also announced that Asus, Dell, HP and Lenovo would be producing hardware that will run Windows 10X and launch in ‘fall 2020’.

What is Windows 10x?
Image: Lenovo

They won’t all be clones: there will be a variety of sizes and specifications. We’ve already had a good look at Lenovo’s ThinkPad X1 Fold, but this was running Windows 10 Pro and therefore lacked the usability that Windows 10X will bring to the device when it’s available in around eight months’ time.

Lenovo has several mockup images (such as the one above) which demonstrate what should be possible with the new OS.