A free open-source launcher runs Valve's official ARM SteamOS, the build made for the Steam Frame headset, in a VM on Apple Silicon Macs, with Proton and FEX handling your Windows games.
steamac, aka FX Steam Launcher, runs Valve's official ARM64 SteamOS for the Steam Frame in a virtual machine on Apple Silicon Macs.
It downloads the real SteamOS image from Valve, checks its signature and handles OS updates.
Windows games run through Proton 11 and FEX, then DXVK or VKD3D, then MoltenVK to Apple's Metal.
ETA Prime got over 70fps in The Witcher 3 and Stellar Blade on an M4 Max, and over 200fps in Left 4 Dead 2. Those were best cases at 1080p or lower.
You need an M-series Mac on macOS 15 or later and about 150GB free. It's unofficial and free on GitHub.
Valve built an ARM version of SteamOS so its Steam Frame headset could play your Windows library. A modder has now taken that exact build and got it running on Apple Silicon Macs. So yes, your MacBook can now pretend to be a Steam Frame, and the results are better than they have any right to be.
The project is called steamac, packaged as the FX Steam Launcher, and it’s free and open source on GitHub.
This isn’t a hacked-up Linux distro or a SteamOS lookalike. The launcher downloads Valve’s official ARM64 SteamOS image, the one made for the Steam Frame, straight from Valve’s servers. It checks the image’s signature against Valve’s own certificate and makes you accept Valve’s licence agreements before it’ll build the disk. It even handles SteamOS updates.
It’s not a native install either. SteamOS runs inside a lightweight virtual machine using libkrun on Apple’s Hypervisor framework, and you can run it windowed or fullscreen while still using macOS around it. The GitHub repo was only created on 4 October, has passed 2,000 stars, and is moving fast: three new versions dropped on 4 November alone, taking it to 1.9.12. There’s a ready-made .dmg download, so you don’t need to build it yourself.
The Steam Deck runs on an x86 AMD chip, same as a gaming PC. The Steam Frame, Valve’s new standalone VR headset, doesn’t. It uses a Qualcomm Snapdragon 8 Gen 3, an ARM chip like the ones in phones and, crucially, like Apple’s M-series. Valve opened pre-orders in September, starting at US$1,059.
To get Windows games running on that ARM chip, Valve paired Proton with FEX, an emulator that translates x86 code to ARM on the fly. Apple Silicon Macs are ARM too, so Valve has basically done the hard part already. The steamac launcher just has to get Valve’s ARM SteamOS talking to a Mac GPU.
And that’s where it gets wild. A Windows game has to go through a stack of translation layers before a single frame hits your Mac’s screen:
We haven’t tried it ourselves, so we’re going off YouTuber ETA Prime, who tested it on an M4 Max. At high settings, The Witcher 3, Stellar Blade and Left 4 Dead 2 all went past 70fps, and Left 4 Dead 2 cleared 200fps.
Before you sell your gaming PC, though, PC Gamer pointed out those were the best cases. Stellar Blade was running at just 800p, nothing went above 1080p, The Witcher 3’s trees looked a bit funky, and not every game ETA Prime tried ran that well. An M4 Max is also one of the fastest chips Apple sells, so a base MacBook Air will be a very different story.
There’s also a security note worth reading if you turn on the experimental DXMT path. The README warns it lets programs inside the VM run code on your Mac with your user’s permissions. Leave it off unless you know what you’re doing. The good news is that controllers are covered: Xbox, DualSense and DualShock 4 pads all work.
This is a brilliant bit of tinkering, and it shows how far Valve’s Linux push has come. Valve didn’t make SteamOS for Macs, but by building it for an ARM headset, it accidentally did a lot of the work. One modder and a pile of open-source translation layers did the rest in about a month.
Is it a reason to buy a Mac for gaming? No. A Mac with enough grunt to run this well costs a bomb, and with RAM prices where they are, even that is getting pricier. But if you’ve already got a decent M-series Mac sitting on your desk, it’s free, it’s easy to try, and your Steam library just got a lot bigger. Mac gamers in NZ and Australia have put up with “not available on your platform” for decades. This is a cheeky way round it.
Got it running on your Mac? Tell us how it went in the GetRekt Discord.
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