Microsoft has officially open-sourced the Windows Subsystem for Linux (WSL), marking a major milestone nearly a decade after its initial release. This announcement was made at Microsoft Build 2025, with the WSL source code now available on GitHub. The open-sourced components include command-line tools (wsl.exe and wslg.exe), background services (wslservice.exe), and Linux-side daemons responsible for networking, launching services, and port forwarding[1].
WSL was first unveiled at BUILD 2016, initially as a compatibility layer (WSL 1) that allowed GNU/Linux environments to run directly on Windows without the need for a full virtual machine or dual-boot configuration. WSL 2, released in 2019, introduced a fully managed Linux kernel running in a lightweight virtual machine, significantly improving compatibility and performance, and enabling features like GPU and systemd support, and graphical Linux applications on Windows desktops[1][3].
The open-source move means developers can now contribute to the platform, create their own variations, and participate in WSL’s ongoing evolution. According to Microsoft, some components remain proprietary, including the WSL 1 kernel driver (lxcore.sys) and file system interface drivers (p9rdr.sys and p9np.dll), which handle integration between Windows and Linux filesystems[3][5].
WSL has become an essential tool for developers, especially those working with open source projects, web development, or Linux software, offering a streamlined environment that uses fewer resources than a full virtual machine. Since Windows 11, WSL can run Linux GUI programs seamlessly alongside Windows applications. With the open-sourcing of WSL 2.0.0, users now benefit from new features such as mirrored networking, DNS tunneling, session 0 support, proxy and firewall support[4].
For those interested in contributing or building WSL from source, details and documentation are available at Microsoft’s GitHub repository and developer blogs[5].