When Valve launched the Steam client for Linux in 2012, the idea of playing Windows games on Linux seemed like a distant dream. Fast forward to 2026, and you can now play tens of thousands of Windows games on Linux — and even on ARM-based handheld devices. This transformation didn't happen overnight. It's the result of over a decade of investment, open-source collaboration, and Valve's determination to break free from platform dependency.

At the center of this revolution are two technologies: Proton, Valve's compatibility layer that lets Windows games run on Linux, and FEX-Emu, an x86 emulator that brings those same games to ARM processors. Together, they've fundamentally changed what's possible in PC gaming beyond Windows.

Here's the complete timeline of how we got here — and what Proton and FEX actually do.

What Is Proton?

Proton is a compatibility layer developed by Valve that allows Windows games to run on Linux without modification. It's built on top of Wine (Wine Is Not an Emulator), a long-standing open-source project that translates Windows API calls into POSIX-compatible calls that Linux can understand.

But Proton is more than just Wine. Valve's version bundles:

The result? You can install a Windows game on Linux through Steam, click Play, and Proton handles everything in the background. No dual-booting. No virtual machines. No manual configuration for most titles.

As of April 2026, ProtonDB reports that over 80% of the top 1,000 games on Steam are playable on Linux via Proton. That's a staggering achievement for a platform that, just a decade ago, had virtually no native game support.

What Is FEX?

FEX-Emu (often just called FEX) is an x86 and x86-64 emulator designed to run x86 Linux binaries on ARM processors. It was created by developer Ryan Houdek and has become critical for bringing PC gaming to ARM-based devices like the Snapdragon-powered retro handhelds we cover on this site. While it began as an independent open-source project, Valve has been quietly funding FEX development for years — and as of Proton 11, FEX is now officially bundled into Proton itself.

Here's the key insight: Proton lets Windows games run on Linux, but most of those games are compiled for x86 processors (Intel/AMD). If you're running Linux on an ARM chip — like a Snapdragon 8 Gen 2 in a Retroid Pocket 5 — you need a way to translate x86 instructions into ARM instructions. That's what FEX does.

FEX uses just-in-time (JIT) compilation to translate x86 code to ARM at runtime, with optimizations to minimize performance overhead. It's not perfect — there's still a performance penalty compared to native execution — but it's shockingly efficient for an emulator of this complexity. The official FEX-Emu website provides documentation, performance benchmarks, and installation guides for various ARM devices.

When combined with Proton, FEX creates a two-layer compatibility stack:

  1. Proton translates Windows API calls to Linux
  2. FEX translates x86 instructions to ARM

The result? You can run Windows x86 games on ARM Linux devices. This is the technology powering Steam support on Snapdragon handhelds running distributions like Rocknix, which we covered recently.

The Timeline: Valve's Linux Journey

2012: Steam Comes to Linux

In July 2012, Valve announced it was developing a Steam client for Linux based on Ubuntu. The beta launched in November 2012, with full public release in February 2013. At the time, fewer than 100 games were available natively on Linux. Valve ported Left 4 Dead 2 and Team Fortress 2 as proof-of-concept titles, demonstrating that Source Engine games could run on Linux with performance on par with — or even exceeding — Windows.

The motivation was clear: Gabe Newell saw Microsoft's push toward a closed Windows Store ecosystem as an existential threat to Steam's dominance. Newell called Windows 8's closed nature "a catastrophe for everyone in the PC space" and argued that Linux would maintain "the openness of the platform."

2013: Steam Machines and SteamOS

In September 2013, Valve unveiled three major announcements in quick succession: SteamOS (a Debian-based gaming OS), Steam Machines (third-party hardware running SteamOS), and the Steam Controller. The plan was ambitious: create a living room gaming platform powered entirely by Linux.

SteamOS 1.0 launched in December 2013. It was built on Linux but still relied heavily on native Linux ports. For Windows-only games, you had to dual-boot or stream from a Windows PC using Steam In-Home Streaming.

2015: Steam Machines Launch (and Struggle)

Steam Machines officially launched in November 2015. They were met with lukewarm reception. The hardware was expensive, the game library was limited to Linux-native titles, and the Steam Controller had a steep learning curve. Critics pointed out that for the same price, you could build a more powerful Windows gaming PC with access to your entire Steam library.

Valve quietly stopped promoting Steam Machines by 2018. But the lessons learned would prove critical.

2018: Proton Changes Everything

On August 21, 2018, Valve announced Steam Play Proton — a fork of Wine specifically tailored for gaming. This was the breakthrough moment. Instead of waiting for developers to port games to Linux, Valve would make Windows games work on Linux automatically.

The initial Proton release supported 27 whitelisted titles. Within weeks, users discovered they could force Proton to run non-whitelisted games by enabling it in Steam's settings. The compatibility floodgates opened.

Proton was open-source from day one, hosted on GitHub, and Valve committed to upstreaming improvements to Wine, DXVK, and related projects. This wasn't a closed ecosystem — it was a collaborative effort that benefited the entire Linux gaming community.

2019–2020: Proton Matures

Over the next two years, Proton expanded rapidly:

By 2020, thousands of Windows games were playable on Linux. Valve's investment was paying off — not for Steam Machines, but for the next big project.

2021: Steam Deck Announced

On July 15, 2021, Valve announced the Steam Deck — a handheld gaming PC running SteamOS 3.0, based on Arch Linux instead of Debian. Unlike Steam Machines, this was Valve's own hardware. And unlike SteamOS 1.0, this version had Proton baked in from the start.

The pitch was simple: your entire Steam library, playable on a handheld. The deck was powered by a custom AMD APU (x86 architecture), meaning Proton could run without additional emulation overhead.

2022: Steam Deck Ships

The Steam Deck began shipping in February 2022. Reviews were overwhelmingly positive. Proton's compatibility had reached a point where the vast majority of Steam's library "just worked" — often with performance matching or exceeding Windows on equivalent hardware thanks to Vulkan optimizations.

Valve also introduced the Deck Verified program, rating games as Verified (perfect compatibility), Playable (minor issues), Unsupported, or Unknown. Developers began optimizing for Steam Deck, even though it was technically just a Linux PC.

2023–2024: Anti-Cheat Support and FEX Development

Two major developments occurred during this period:

1. Anti-cheat compatibility: Valve worked with BattlEye and Easy Anti-Cheat to support Proton, unlocking multiplayer games like Elden Ring, Apex Legends, and Dead by Daylight. This was a massive barrier removed.

2. FEX matured rapidly: Ryan Houdek's FEX-Emu project progressed from experimental to functional. By late 2023, FEX could run complex x86-64 Linux applications on ARM with playable performance. The Asahi Linux project (reverse-engineering Linux for Apple Silicon Macs) adopted FEX for x86 compatibility, proving its viability.

2023–2025: Valve Secretly Funds FEX Development

In a revelation that didn't surface until late 2024, it became clear that Valve had been quietly funding FEX-Emu development for years. While Ryan Houdek led the project publicly, Valve's financial backing helped accelerate development significantly.

This was strategic positioning. Valve wasn't just supporting an interesting open-source project — they were building the infrastructure needed for ARM-based gaming devices. By 2025, Linux distributions for Snapdragon-based retro handhelds began bundling FEX and Proton together. Rocknix was one of the first to offer this out-of-the-box, allowing devices like the Retroid Pocket 5 and AYN Odin 2 to run Steam games.

April 2026: Proton 11 Officially Integrates FEX

The biggest news in the Proton timeline arrived in April 2026 when Valve released Proton 11.0-Beta1 with integrated FEX-2604 support. This was the first time Valve officially bundled FEX directly into Proton, making ARM64 support a first-class feature rather than a community workaround.

The technical implementation is elegant: when Steam launches a game on an ARM device, Proton provides the Windows API compatibility layer as usual, but when the game binary is x86/x64, FEX sits underneath Proton as the execution engine, translating CPU instructions to ARM64 via just-in-time compilation. Because Proton's own components are compiled as ARM-native where possible, the translation overhead is limited to just the game's original x86 code.

Performance results were impressive: According to Notebookcheck testing, Hollow Knight: Silksong ran above 100 FPS on the AYN Odin 2 Portal's Snapdragon 8 Gen 2 chip, Half-Life 2 exceeded 120 FPS, and even Cuphead maintained 60–70 FPS.

The primary driver for this integration is the Steam Frame — Valve's upcoming streaming-first gaming headset powered by a Qualcomm Snapdragon 8 Gen 3 ARM processor. By baking ARM compatibility into Proton now, Valve is building the software foundation for the Steam Frame to run a subset of games locally, not just stream them.

But the community impact extends far beyond Valve's hardware. Modders successfully got Steam running on a Nintendo Switch running Ubuntu Linux, and the integration works on ARM handhelds from manufacturers like AYANEO, Retroid, and AYN with no modifications required.

Why This Matters for Retro Handhelds

For retro gaming enthusiasts, FEX and Proton unlock a new category of games on ARM handhelds:

This wouldn't be possible without Valve's decade-long investment in Linux gaming. Proton is open-source, freely available, and actively maintained. FEX builds on that foundation, extending compatibility to ARM — a chip architecture Valve never directly targeted but benefits from nonetheless.

The Ecosystem Today

As of April 2026, the Proton + FEX ecosystem looks like this:

This is an open-source success story. Valve's investment didn't just benefit Steam — it lifted the entire Linux gaming ecosystem. Other storefronts like GOG and Epic Games now run on Linux through tools like Heroic Games Launcher and Lutris, all leveraging the same Proton/Wine foundation. And with Proton 11's ARM support, that ecosystem now extends to ARM-based devices regardless of manufacturer.

What's Next?

Looking ahead, several trends are shaping the future of Proton and FEX:

Final Thoughts

When Valve launched Steam on Linux in 2012, skeptics dismissed it as a side project. Fourteen years later, Proton 11 with official ARM support represents the culmination of Valve's long-term vision — a gaming platform independent of both Microsoft's control and Intel/AMD's x86 architecture.

Proton turned Linux into a first-class gaming platform. FEX extended that compatibility to ARM. And Proton 11's integration of FEX makes it official: Valve is betting on a future where your CPU architecture doesn't determine what games you can play.

For retro handheld enthusiasts running Rocknix, Bazzite, or other Linux distributions, this history matters. The fact that you can boot into EmulationStation, play Ocarina of Time through a recomp, switch over to Steam, and launch Hollow Knight: Silksong at over 100 FPS — all on a $200 Snapdragon handheld running Windows x86 games through two layers of translation — is a direct result of Valve's willingness to invest in open-source infrastructure that benefits everyone, not just Steam Deck owners.

That's worth recognizing.