Amazon has just taken the wraps off its long-rumored Amazon Luna, meaning the company is officially jumping into the cloud gaming ring — one that has become increasingly crowded over the past year. Google launched Stadia last November, Nvidia’s GeForce Now left beta in February, and Microsoft’s cloud gaming offering (formerly known as xCloud) is included with a Game Pass Ultimate subscription as of September 15th, though it only works with Android right now.

The race is on to see which (if any) of those cloud gaming services takes off with customers, and each company is tackling cloud gaming in a slightly different way. If you’re trying to better understand each service, we’ve put together this guide for you.

Amazon Luna

Amazon’s Luna offers all-you-can-play access to different selections of games as part of separate “channels” — which sounds almost like a cable service. But at launch, you can only subscribe to one channel, Luna Plus, and only if you’re accepted as an early access user. The only other channel announced so far is one that’ll house exclusively Ubisoft games. And right now, you can’t buy individual games on Luna — you can only play what’s included in the bundles. Luna Plus will have “introductory pricing” of $5.99 per month, while the Ubisoft channel, which is currently listed as “coming soon,” doesn’t have a price yet.

Games will stream from Amazon’s AWS widely-used cloud computing infrastructure (specifically G4 instances), with the promise of loading very quickly with no installation required on your part. And if you buy the custom $49.99 Luna Controller offered to Luna early access users, you can connect it directly to those servers while you’re playing, which Amazon claims will mean less latency in gameplay than if you’re using the controller over a Bluetooth connection.

Luna will be available on PC, Mac, Fire TV, and, in a notable distinction from its competitors, on iPhone and iPad. The iOS version of Luna is a progressive web app, according to Engadget, a solution that allows Amazon to circumvent Apple’s restrictive App Store rules for cloud gaming apps. Games will target up to 1080p, with 4K support “coming soon” for some games, according to the Luna website.

Amazon plans to have about 50 games each on both the Luna Plus and Ubisoft channels, the company told Engadget. That number might be surprisingly easy to grow over time, as Luna runs on Windows servers and Nvidia GPUs in Amazon’s AWS compute cloud, so developers can bring their existing Windows games over to those to get them running on Luna.

That might be an easier lift for developers than it is to bring games to Stadia, which requires developers to port their games to Linux so they can run on Google’s server hardware — and it doesn’t hurt that plenty of companies have been bringing their console games to PC recently, including Sony.

Luna will also have an integration with Twitch that lets users watch streams and start games they’re watching others play, but Amazon hasn’t said when that might be available.

You can sign up now for a chance to try out the service in early access.

Google Stadia

Google’s Stadia cloud gaming service seems pretty similar to Amazon’s Luna at first glance — it lets you stream games from Google’s distributed data centers directly to the device you’re playing it on, similarly has a custom controller that can connect to Google’s servers to reduce latency, and promises to prominently integrate YouTube. But the business model for Stadia has some notable differences.

Instead of cable-like channels, Stadia gives you access to games two different ways. One is to buy individual titles at full price and stream them whenever you want, at no additional charge.

Or, you can get Stadia Pro, a $9.99 per month subscription service that lets you claim a regularly-changing lineup of games for free, and keep them as long as you pay the monthly fee. Stadia Pro also lets you play games you buy individually at up to 4K resolution, up from the 1080p max resolution that’s available to non-Pro users.

Getting developers to bring games to Stadia might be a bit more of a challenge than it is for other platforms, though — as I mentioned earlier, developers need to port their games to Linux. Also, since you’re always buying a fresh copy of a game on Stadia, you’ll sometimes be leaving your friends and savegames from other platforms behind. We found the Destiny 2 and PUBG servers pretty empty back in May. It’s not yet clear if that will be true for Amazon’s Luna as well.

But unlike Luna, the Stadia platform also has (some) exclusive games and features made possible by the cloud, and is building games for Stadia itself. Amazon hasn’t said whether it’ll commit its own game studios or server infrastructure to do something similar, but told reporters it’s “not focused on things like exclusives” for Luna.

Stadia is available on a slightly different mix of platforms than Luna: PC, Mac, Linux, ChromeOS, the Chromecast Ultra dongle for TVs, and certain Android phones — but no iOS support. We counted 88 games on the service as of this writing.

Microsoft Game Pass Ultimate streaming, aka xCloud

If you subscribe to Xbox Game Pass Ultimate, which costs $14.99 per month and is already available in 22 countries, you can beam more than 150 Xbox games from Microsoft’s data centers directly to the device you’re streaming them to. But as I said in the introduction, there’s the big caveat that you can only stream games to Android phones right now — though Microsoft does plan to bring its cloud gaming service to PC at some point.

There’s another thing you should know about Microsoft’s cloud gaming service: it’s currently powered by Xbox One S hardware in Microsoft’s data centers. That means the games you’re playing might have worse graphics and slower load times than other cloud gaming services, which run on beefy servers. Even the best internet in the world won’t help the physical hardware in an Xbox One S load a game any faster. Though Microsoft plans to upgrade to Xbox Series X hardware in its servers next year.

That being said, because your saves are all stored in Microsoft’s cloud, it’s easy to move between playing games on your Xbox (many of which are also included in Xbox Game Pass) and an Android phone. You’ll be playing with other Xbox players online as well. And if you don’t want to use Microsoft’s cloud gaming service, you can stream games directly from your Xbox console to an Android phone or tablet that’s on the same Wi-Fi network, which might result in a higher quality stream to your device.

Microsoft is also in a good position to continue to add games to the service, because in theory, any game that comes to Game Pass could also be available via Microsoft’s cloud. (Microsoft itself adds first-party titles to the service the day they are released.) And again, since it’s Xbox hardware in a server rack, there’s no porting required for a developer to bring their game from Xbox to Game Pass streaming — developers just have to make the decision whether or not they want their games available in the cloud.

Nvidia’s GeForce Now

Nvidia’s approach with GeForce Now is to let you play PC games you already own, without needing a powerful PC right in front of you, and typically bringing your savegames along for the ride. And the company says there are more than 2,000 games available to stream on GeForce Now — which is quite a bit more than any of the other three services we’ve covered here.

But again, we’re generally talking about games you already own, which is why that number is so high — and even so, not all developers have agreed to let you play your own titles. It’s been opt-in ever since the turbulence after GeForce Now’s official launch in February, when big developers like Activision Blizzard and Bethesda yanked their titles off the service.

We don’t know exactly why the developers pulled their games, but it seems Nvidia failed to get permission to continue letting players stream many games once GeForce Now moved from a free beta to a paid service. However, there are still some notable developers that have opted in to GeForce Now, including Bungie, Electronic Arts, Riot Games, and Valve.

If you choose to pay $4.99 per month for GeForce Now’s “Founders” tier, you can play your games as much as you want and take advantage of the company’s ray-tracing-capable RTX Server graphics cards while you’re streaming them for an added graphical boost.

But GeForce Now is unique in that you don’t necessarily need to pay at all just to try — there’s also a free tier that lets you play games for an hour at a time, and you can download some of the hottest free-to-play games like Fortnite, League of Legends and Destiny 2 if you don’t already have compatible titles in your Steam, Epic Games or Uplay libraries. The free tier also runs on somewhat less graphically powerful servers, without ray-tracing support.

GeForce Now works on PC, Mac, Android, the Nvidia Shield, some Chromebooks, and tops out at a maximum resolution of 1080p at 60fps for now.

Update September 25th, 8:34PM ET: Added that Microsoft’s cloud gaming service is available in 22 countries, will come to PC at some point, and that first-party titles are on the service the day they release.