To ensure games run well on Linux either via Native Linux builds or Windows games with Proton, part of the magic is in the Steam Linux Runtime. A new version of it, the Steam Linux Runtime 4.0 was recently put up with some pretty big changes.
What’s the point of it? It ensures Steam and games run through Steam on Linux work properly across all the many different Linux distributions. Another secret Valve sauce for Linux. Well, not secret at all but you get my meaning I’m sure.



Funny this shows up when all of a sudden Steam won’t launch anymore on my Arch install. It’s installed via flatpak.
How do I even check which version of the Steam runtime I am running? The flatpak version of Steam is just 1.0.something.other.
The runtime is not Steam itself. That’s more or less independent from the runtime. The runtimes are a collection of libraries that developers can develop against without having to include them themselves.
Kind of similar to the Visual C++ Runtime on Windows.
I know what a runtime is, but I’d like to check which version of it I’m running. 🙂 Wouldn’t be very difficult but I’m this instance I don’t know how.
The runtime is for launching games, not Steam itself. You can check the runtime selection in Compatibility tab of Steam and of each game. If your Steam Flatpak install doesn’t work, the issue is likely somewhere else.
I’d suggest trying to launch the flatpak from the terminal and seeing if there’s any strange logging.
Hold up, are you talking about the compatibility layer, “Proton”? I’m not sure that’s what we’re talking about here. Proton is up to version 9 and 10, not 4.0.
You can select Steam Runtime Versions in the Compatibility tab too, separate from Proton versions
Oh okay, I guess that’s in the main Steam settings, not per game as the other person suggested.
You can select it per game as well,
steam runtime 3.0and now presumablysteam runtime 4.0should show up in the same drop down menu next toproton 1.0,proton 10.0in the compatibility optionsAnd also, should be noted, only for games with a Linux native version
No, it is a per game setting. When your game is a native Linux game it will use one of the Steam runtimes. If you had a Linux native game and selected Proton instead of a Steam Linux runtime Steam would download the Windows version of the game.
With Linux native games you usually don’t have to touch this setting.
Already did that but I couldn’t see anything that I could recognize as abnormal. The “Connecting” window shows up, actually. But it just stops loading for a second and then it just says “Reaping pid” in the console and it closes the process.
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So you can use those to develop on a platform and be sure that it work on the other too? Is this runtime steam-indipendent?
Yes. Exactly.
Older stuff here: https://github.com/ValveSoftware/steam-runtime
Newer stuff here: https://gitlab.steamos.cloud/steamrt
The dev guide within that gitlab repo confirms that it can be used sans Steam: https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/blob/main/docs/slr-for-game-developers.md
This applies to the new runtime as well: https://gitlab.steamos.cloud/steamrt/steamrt4/platform
Oh that’s cool, thank your for the link too
idk about that, but it’s called the Steam Runtime because it’s the library files for running Steam. so I’m not sure what context you would use it in that didn’t include Steam, since it’s used for everything Steam does from connecting you to your friends in multiplayer games, to notifying Steam users that it’s their turn in asynchronous games.
if the game wasn’t run from Steam, it probably wouldn’t need or want to use the Steam Runtime.
No, it’s for running games on Linux. Steam will probably use the libs as well for its own functionality. But the main use is for game developers to target specific libraries so that they are independent of the user’s distribution.
And they can indeed be used outside of Steam as well. I sometimes use it to link in specific libraries for other games. @Axolotl_cpp@feddit.it
Thank you!
I stand corrected then
the flatpak version is unsupported by Valve for a reason. there’s been a ton of problems over the lifespan of the flatpak. it’s usually highly recommended everywhere not to use that version.
You say that as if the versions packaged by your distro are supported.
As it stands, on Linux, Steam is only supported by Valve on SteamOS and LTS releases of Ubuntu.
Seems like I’m not the only one with this issue.
I’ve been using Steam in a flatpak for a couple years now, I think. What ton of problems are you referring to?
I don’t have a reference, but I’ve been seeing random individuals asking for help and finally saying they fixed their issue by switching away from flatpak, so… You, I guess? Your.problem might be a perfect example of one of the many problems that keep popping up, that seem to only happen on the flatpak version.
For me personally (Fedora 43 KDE) about 80% of unity games that don’t have a native build refused to run at all. No problems at all since I swapped to a non-flatpak Steam install.
OTOH I’m having trouble with pretty much all flatpak apps in some way or another… might just be my system that’s being weird.
too many small things over the years to go over them all in one post. some still relevant, some not. drivers, for one. no game mode, if I remember correctly. you might end up having issues with controllers, and VR is out of the question on the flatpak. some people have reported issues with permissions.
it’s enough of a troublemaker that Bazzite blacklisted the flatpak, I believe, and it can’t be installed normally.
Install warehouse. It gives you all the details of which runtime is in a Flatpak and even lets you change the version.
I did not know about Warehouse. Thank you.
i usually avoid flatpaks, especially with steam. but every now and then my non-flatpak steam borks too and won’t launch on mint. 9 times out of 10 simple reboot helps, but sometimes it requires a reinstall…
#justFlatpakThings
Why would you use flatpack for stuff natively available on pacman? Search no further, flatpack is a good way to introduce problems where there are none
https://wiki.archlinux.org/title/Steam#Flatpak
🤷♂️ Seemed like a good way to install it. I had used the native package before but I think I tried flatpak because of some issue or another with the native version.
It’s been working great for years now so, no issues until now.
I usually install big corporate software with flatpak if I can help it, to keep them as isolated as possible. Slack, Discord, Steam, etc. Stuff like that. 👍
You’re not alone. I had the same thing on two machines yesterday. (Not flatpack)
yeah, many people had that problem. it happened around the same time the Arc Raiders servers went offline. a buddy of mine couldn’t launch Steam, and when he did, it wouldn’t load his friends list. my theory is that the 350,000 people who were all reloading Steam and Arc Raiders over and over DDoSed the two services.
Been happening though. Maybe it’s a coincidence or it’s happening again or something. Interesting theory though.
A decent error message would have been useful.
I don’t know if there’s an existing error message for “please stop reloading Steam all at once, the game will come back online just give them time”.
“unable to contact server” would do. It tells me it’s not a problem on my end.