The service lets you access a library of Xbox 360 and Xbox One games, even letting you download them to play offline. Read on to find out about the pricing, features, and which games are on offer.
How much does it cost?
The monthly subscription fee is £7.99/$9.99, which is substantially cheaper than the £12.99/$19.99 monthly rate for PlayStation Now, the service's closest rival.
There's no option to rent individual games, but there's a 20 percent discount if you decide to purchase any of the games while they're still part of the Game Pass catalogue, with a further 10 percent off any DLC or other related purchases - though that only applies to Xbox One titles, not the 360 games.
What is the Xbox Game Pass?
Simply put, it's a monthly subscription service that gives you access to an extensive library of Xbox One and Xbox 360 games, all playable on your Xbox One console.
It's similar to Sony's rival PlayStation Now platform, but unlike PS Now, you don't stream the games - instead you have to download and install any that you want to play.
The downside is that you need to have enough hard drive space to install them, and will always need to wait for downloads before you can play, but the upshot is no worrying about streaming lag or connectivity issues. Microsoft has also said that there is no limit on the number of games that you can install at any given time, and you can play downloaded games offline for up to 30 days.
There should be over 100 games on the platform at any given time, drawn from both the Xbox One and Xbox 360 back catalogues, but the library regularly rotates, with new games added each month and others taken away. Once games leave Xbox Game Pass you can't play them any more, but your progress and achievements will be saved.
As mentioned above, if you fall in love with a title you can choose to buy it so that you own it permanently, and you'll get a 20 percent discount, along with 10 percent off any DLC - but only if you make the purchase before the game leaves Game Pass, and only if it's an Xbox One game.
It's worth noting that while Xbox 360 games are included in the service, Game Pass itself is only available on the Xbox One, and not the older console. It will also be compatible with Project Scorpio when that launches later in 2017. Microsoft also hasn't announced any plans for a similar Windows service.
Finally, you don't need an Xbox Live Gold account to use Xbox Game Pass, though you will need it if you want to enjoy any of the online multiplayer features in games.
What games can I play?
Xbox Game Pass has over 100 games from the Xbox One and Xbox 360 on the service at launch, but the lineup will change over time, with new titles added "every month".
Xbox Game Pass senior product manager Dennis Ceccarelli clarified during E3 2017 that "at least" five new games will be added to the service on the first of the month, every month, and that no games will leave the service until at least November 2017.
"In reality, the vast majority of our games are going to be in there much, much longer than that so you've got plenty of time to play through the great experiences that are in Game Pass, engage with DLC, just really enjoy that content - it's not leaving tomorrow."
The launch games included Halo 5: Guardians, Mad Max, Payday 2, NBA 2K16, Saints Row IV, Terraria, Lego Batman, Fable 3, the Gears of War series, and SoulCalibur II.
Microsoft is working with major publishers including 2K, 505 Games, Bandai Namco, Capcom, Codemasters, Deep Silver, Focus Home Interactive, SEGA, SNK, THQ Nordic, and Warner Bros, so there should always be a decent variety of titles available.
To see a full list of titles on the service at any given time, head to the official Xbox Game Pass site and scroll down the page. You can also check out our round-up of the best Xbox One games to get an idea of which games to prioritise playing.