One weakness of Valve’s Steam Deck gaming handheld and SteamOS is that, by default, they will only run Windows games from Steam that are supported by the platform’s Proton compatibility layer (plus the subset of games that run natively on Linux). It’s possible to install alternative game stores, and Proton’s compatibility is generally impressive, but SteamOS still isn’t a true drop-in replacement for Windows.

Microsoft and Asus’ co-developed ROG Xbox Ally is trying to offer PC gamers a more comprehensive compatibility solution that also preserves a SteamOS-like handheld UI by putting a new Xbox-branded user interface on top of traditional Windows. And while this interface will roll out to the ROG Xbox Ally first, Microsoft told The Verge that the interface would come to other Ally handhelds next and that something “similar” would be “rolling out to other Windows handhelds starting next year.”

Bringing a Steam Deck-style handheld-optimized user interface to Windows is something Microsoft has been experimenting with internally since at least 2022, when employees at an internal hackathon identified most of Windows’ handheld deficiencies in a slide deck about a proposed “Windows Handheld Mode.”

Credit: Microsoft/Twitter user _h0x0d_ The mock-up “gaming shell” that some Microsoft employees were experimenting with in 2022 shares some similarities with the Xbox-branded interface we saw on the ROG Xbox Ally yesterday.

It’s not clear whether this new Xbox interface is a direct outgrowth of that slide presentation, but it pitches a tile-based Switch-style gamepad UI with some superficial similarities to what Microsoft revealed yesterday. This theoretical Handheld Mode would also have come with “optimizations for your handheld’s touch screen to improve touch points and visibility” and Windows’ “lack of controller support” outside of the Steam app and actual games.

On the ROG Xbox Ally, the new full-screen interface completely replaces the traditional desktop-and-taskbar interface of Windows, saving what Microsoft says is a couple of gigabytes’ worth of RAM while also using less energy and other system resources. On a handheld running the normal version of Windows, like the regular ROG Ally, that Windows overhead is joined by additional overhead from things like Asus’ Armoury Crate software, which these handhelds currently need to bridge the functionality gap between SteamOS and Windows.