Microsoft previously stated that its plan for Windows 10 was to have it reach 1 billion devices by 2018. Now, it’s becoming clear how Microsoft will do that: by bringing the operating system to non-Windows devices.

The company on Tuesday announced that a Windows 10 companion app will be available for iOS and Android devices alongside the main version for Windows devices.

“A real challenge people face is figuring out how to make everything work together,” Microsoft’s Joe Belfiore wrote on the Windows blog. That’s why we’re announcing a ‘Phone Companion’ app built-in to Windows 10, which will help you connect your Windows PC to whatever phone you own–whether it’s a Windows phone, Android phone, or iPhone.”

Once you sync up your iPhone or Android device, you’ll be able to access your files and content across PC and phone. Check out the full blog post for a detailed breakdown of how this works.

In addition, Microsoft announced today that Windows 10’s Siri-like digital assistant Cortana–named after the Halo character–will also be available for iPhones and Android devices. Cortana can fetch net-based data such as web results and weather reports, among many other things.

However, there will be some limitations.

“Although the functionality will be very helpful, because it’s “just an app” there will be certain things that Cortana does on Windows phones that won’t work on Android devices or iPhones,” Belfiore said. “Some features require access to the system that aren’t currently possible with iOS or Android, so things like toggling settings or opening apps won’t initially be available in the Cortana companions for those platforms. Similarly, the ability to invoke Cortana hands-free by saying ‘Hey Cortana’ requires special integration with the device’s microphone, so that feature will be limited to Windows Phones and PCs.”

Windows 10 launches this summer, first on PC. The new operating system will also be integrated into the Xbox One, but not until “post-summer.”