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Microsoft has officially open-sourced the Windows Subsystem for Linux (WSL) as announced at Build 2025. The source code, except for a few components, is now available on GitHub, marking a major milestone for the project that began as an experiment nearly a decade ago[1].

This move enables the developer community to contribute directly to WSL, including its command-line tools (wsl.exe and wslg.exe), background services (wslservice.exe), and Linux-side daemons responsible for networking and port forwarding[1]. The kernel driver for WSL 1 (lxcore.sys) and the file system drivers (p9rdr.sys and p9np.dll) remain proprietary and are excluded from open sourcing[3].

WSL allows developers to run unmodified Linux tools, utilities, and applications directly on Windows—without the overhead of a full virtual machine or the need for dual-booting. WSL 1 provided a compatibility layer for Linux binaries by converting system calls to Windows, while WSL 2, released in 2019, features a real Linux kernel in a lightweight virtual machine for greater compatibility and performance[2].

With continued improvements—such as GPU acceleration, GUI support via WSLg, and systemd support—WSL has become a critical tool for developers. Since 2021, WSL development has been decoupled from Windows itself and shipped as a standalone package through the Microsoft Store, enabling faster updates and broader compatibility[5].

WSL 2.0.0’s release introduced features such as mirrored networking, DNS tunneling, session 0 support, proxy support, and firewall integration, continuing to enhance its network and security capabilities[4]. In the latest Windows 11 version 24H2, WSL is no longer embedded directly into the OS image; instead, wsl.exe is still present to bootstrap installation of the latest WSL package[3].

Microsoft’s open-sourcing of WSL fulfills a long-standing community request and is expected to accelerate innovation and bug fixes via community contributions[7].

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