There seems to be some confusion brewing on what games will actually run on the Steam Deck, so let this serve as a reminder on keeping expectations in check. Here's a quick refresher of how things are right now.
Some of the confusion seems to appear from an IGN interview, where Valve developer Pierre-Loup Griffais mentioned how "we haven't really found something that we could throw at this device that it couldn't handle" that we covered before. Here's the thing though: even though the Steam Deck will ship by default with the Arch Linux based SteamOS 3, they have also been testing Windows 10 and they've been working with AMD to get it supported on Windows 11 too. So speaking from a hardware standpoint, yes it probably will work with the vast majority of games on a performance level.
For regular readers and regular Linux gamers, knowing that the Steam Deck won't run everything is a given and this won't be news but there's plenty of people out there seemingly expecting a bit too much from it. Part of the problem though is Valve's marketing too, with it repeatedly mentioning your entire Steam library. They obviously want every game to work but that's simply not going to be the reality - at least not for a while.
For people who stick with SteamOS 3 this is where it doesn't quite match up. There's a good number of native Linux games (those actually built for Linux) and for everything else there's Steam Play Proton to run Windows games. A big majority of games work on Linux already between native and Proton but there's caveats.
Currently, Proton does not work with games that have the likes of Easy Anti-Cheat and BattlEye which is used in some of the most popular online titles. When it comes to EAC and BattlEye, we do know that Valve are working on it as they said in the developer documentation FAQ that they're "working with BattlEye and EAC to get support for Proton ahead of launch".
Another issue is Microsoft Media Foundation for videos, it's something of a nuisance and they don't play in Proton either. Currently Valve appear to be re-encoding the videos into a playable format which downloads with your game when run through Proton. That's a lot of work though too, there's a lot of games on Steam.
Then there's certain DRM too. Valve's older CEG (custom executable-generation) DRM also doesn't work in Proton, and there's no doubt a few other DRM/anti-tamper solutions that also don't work with Proton. Launchers can be a problem too, with some developers using .NET / Windows Presentation Foundation (WPF). For launchers Valve recommends that developers use something cross-platform and standalone like Qt or just skip launchers completely, which would be vastly better for gamepad/controller support too.
Compatibility will improve over time though as more developers hopefully look to support it directly and as Proton continues maturing. So even if your favourite or the latest AAA doesn't work right away, it might do later. There's still plenty of time until the Steam Deck releases and Valve has opened up requests for developer kits too. Valve also stated in their Steamworks video how "our goal is for every game to work by the time we ship Steam Deck" and that "there is a lot of work that has been done that doesn't yet affect the public version of Proton" so we are expecting the situation to improve. Until we see this special Proton release though, this article sums up the current situation.
If you're looking to try out Linux gaming and you're confused with Proton, be sure to check out our guide.