Apple just handed Microsoft a major win for its newest version of Windows

Apple CEO Tim Cook

Apple's iTunes -- and with it, the company's subscription music service -- is heading to Microsoft's Windows Store. 

Microsoft announced the move Thursday at its Build developer conference in Seattle. Apple will be listing a full version of iTunes, complete with Apple Music and iPhone syncing, in the Windows Store. 

This is a big deal for Microsoft. Just last week, the software giant announced Windows 10 S, a streamlined version of its flagship operating system that's targeted at students. Unlike other versions of the OS, Windows 10 S can only install apps from the Windows Store. Adding iTunes will make Windows 10 S a lot more useful and usable to a lot more people.

From the Apple perspective, this could be seen as a defensive move. Currently, iTunes is the only way on a Windows or Mac computer to use the Apple Music subscription service, which is a major push for Apple. If iTunes weren't in the Windows Store, Apple Music could lose out to rivals such as Spotify.

At the moment, the Windows Store is fairly limited. It includes a handful of popular apps like Netflix, Hulu, Facebook, Instagram, and Uber, but it's struggled to attract the lion's share of developers. Most app makers are focusing their efforts on Apple's iOS, which underlies the iPhone, and Android, both of which offer broader audiences. Meanwhile, traditional Windows developers generally haven't bothered with the Windows Store, seeing little advantage in changing how they distribute software.

As a result, Windows 10 S lacks access to many popular desktop apps, including the Steam gaming platform and the Google Chrome browser. That's likely to limit its appeal. 

Which is why Microsoft has redoubled its efforts to get the Windows Store stocked up. At the Build, the company announced that Spotify, SAP Boardroom, and Autodesk are all coming to its Store. The idea is that the more developers that come to the Windows Store, the more it'll encourage others to follow suit.

So with Apple giving the Windows Store this a vote of confidence, that's a huge win for Microsoft. As we often see elsewhere, as Apple goes, the world follows.