At the recent BUILD event, Microsoft unveiled a significant milestone in its ongoing development of the Windows Subsystem for Linux (WSL): it is now open source. This announcement marks the culmination of nearly a decade of evolution, during which the team has diligently worked to refine and enhance this powerful tool.
Closing a Chapter
In a notable gesture of transparency and community engagement, Microsoft has officially closed issue #1 on its GitHub issue tracker. This particular issue, which has lingered since April 6, 2016, posed a simple yet profound question: “Will this (WSL) be Open Source?” With this transition, developers and enthusiasts alike can now access the WSL code, build it from source, and contribute enhancements and fixes, fostering a collaborative environment for innovation.
A Glimpse into WSL’s Evolution
WSL serves as a virtualization framework that empowers Windows users to seamlessly run Linux distributions alongside their Windows operating system. Initially, WSL 1 was built on a pico process provider called lxcore.sys, enabling the execution of ELF binaries and Linux system calls directly within the Windows kernel. In a bid to enhance compatibility with native Linux, Microsoft introduced a dedicated Linux kernel in 2019, further bridging the gap between the two operating systems.
Over the years, WSL has undergone substantial enhancements, including the introduction of GPU support, graphical applications through wslg (which is already open source), and systemd support, which is crucial for many Linux distributions. In 2021, Microsoft made a strategic decision to decouple WSL from the Windows codebase, allowing for more agile updates and responsiveness to community feedback. This standalone version of WSL debuted via the Microsoft Store, initially supporting only Windows 11 and catering to users eager to explore cutting-edge features.
Continued Innovation
With the launch of WSL 2, users experienced a host of improvements, such as mirrored networking, DNS tunneling, and enhanced firewall and proxy support. By 2025, WSL further refined the installation process for Linux distributions, allowing users to leverage local images independent of the Microsoft Store.
Reflecting on the journey, Senior Software Engineer Pierre Boulay emphasized the vital role of the community in shaping WSL’s trajectory. “WSL could never have been what it is today without its community. Even without access to WSL’s source code, people have been able to make major contributions that lead to what WSL is now,” he noted in a recent blog post.
