Microsoft is planning to launch its game streaming service, currently known as Project xCloud, free to its paying Xbox Game Pass Ultimate subscribers in September. The xCloud service will allow Xbox players to play games on mobile devices or even start a game on their consoles and resume it on their phone or tablet. Xbox Game Pass Ultimate combines Xbox Live access, an Xbox Game Pass subscription, and, starting in September, xCloud game streaming into a single $14.99 monthly subscription.

Microsoft is promising that more than 100 Xbox Game Pass titles will be playable on a phone or tablet when the streaming service launches. Microsoft isn’t detailing which countries will be supported at launch just yet, though. The company has been building out its Azure data centers across the US and in parts of Europe with Xbox One S blades to stream Xbox games through xCloud. Microsoft will upgrade these servers to Xbox Series X hardware in 2021.

Xbox Game Pass Ultimate will be the only way to access xCloud streaming at launch, but it won’t always be limited to Microsoft’s top subscription tier.

“Over time we will continue to expand how we introduce streaming as part of the platform, and playing games that you own that aren’t part of the subscription,” says Microsoft’s Xbox chief Phil Spencer in an interview with The Verge. “For launch we’re putting it in Ultimate for no additional cost. We think it’s a good audience for us to start with, and it’s an audience that plays a lot of games.”

While everyone accessing xCloud game streaming in September will do so through a phone or tablet, Microsoft isn’t detailing which devices will be supported just yet. The software maker has been involved in ongoing discussions with Apple over App Store policies that have prevented Microsoft from testing xCloud with the same features as the Android version. Microsoft started testing xCloud on iOS devices earlier this year, but the test has been limited to a single Halo game.

“We want to bring xCloud, eventually, to every screen that someone can stream games to. Right now we’re just saying mobile,” says Spencer. “There are discussions going on and we’re working through things. We’ll talk more specifically about which mobile devices through August and the September launch.”

It sounds like we’re going to get more details on the xCloud launch in general in August. I also asked Spencer about the promised PS4 controller support and streaming xCloud games to PC, and he promised more clarity on the company’s plans next month.

Project xCloud won’t even be the final name for Microsoft’s game streaming service. “This isn’t the official name, but you should think about it as Game Pass streaming or Xbox streaming, something like that,” explains Spencer. “We actually don’t have the final name just yet, but it won’t be Project xCloud.”

Beyond the launch plans, Microsoft has greater ambitions with xCloud that go beyond just streaming to mobile devices. “There’s an ease of browsing and buying capability on xCloud that I find incredibly valuable today,” says Spencer. “Many times the first time I play a game will actually be on xCloud, so I can go and use it as my snackable trial experience.”

Microsoft is planning to use xCloud as a vehicle for enabling people to quickly try out Xbox games. That could involve you logging into an Xbox console and seeing a friend playing a game and quickly joining in before your full download has completed, for example, or simply clicking a link from Facebook Gaming in the future.

“We want that trial to be as easy as it is in music and video today, where I can send you a track in Spotify today and you can stream it instantly,” says Spencer. “Over time, anywhere I see a game I should be able to give it a try.” The idea is that any time you see a game on any device or web browser, you should be able to start streaming it through xCloud in the future.

Some of these xCloud ambitions sound similar to what Google has promised with Stadia. Google’s big plan is to leverage YouTube to allow people to jump straight into games. That hasn’t materialized just yet, but the ease of accessing games feels like it will be an important part of both xCloud and Stadia in the future.

Some rival streaming services, like Nvidia’s GeForce Now, have run into trouble with publishers by offering their games to stream without their permission. Microsoft hasn’t run into any similar problems with publishers yet. “Over 100 games will be there,” says Spencer. “We have an existing relationship with so many publishers already, so for us the conversation is how do we take the great business that we’ve built together as a platform, and as a studio or publisher and expand it.”

That doesn’t guarantee that every Xbox Game Pass game will necessarily be available on xCloud game streaming, but it certainly sounds like the vast majority will be. A lot of game developers have benefited from increased sales, thanks to Xbox Game Pass, especially indie developers who see the immediate benefit of access to more than 10 million subscribers.

Microsoft is now planning to show more games coming to xCloud during its Xbox Series X games event next week, and we should get more solid launch details about the service in August.

Microsoft has been building toward this xCloud launch for the best part of a decade, ever since the company first demonstrated Halo 4 running on a Windows Phone back in 2013. After nearly a year of publicly testing xCloud, September will mark the first big step toward Microsoft’s ambitious plan to reach billions of gamers around the world.