Microsoft has taken a significant step in its relationship with the open-source community by open-sourcing its Windows Subsystem for Linux (WSL) code. This announcement, made during the Build 2025 developer conference, addresses a long-standing request from developers and marks a pivotal moment in the collaboration between Microsoft and open-source contributors.
WSL: Bridging Two Worlds
For those unfamiliar, WSL allows users to run Linux distributions natively on Windows, creating a seamless integration between Linux tools and the Windows environment. Since its debut at Build 2016 and its subsequent release in the Windows 10 Anniversary Update, WSL has become an essential tool for developers who require access to Linux utilities and command-line tools without exiting the Windows ecosystem.
The primary motivation behind WSL’s creation was to provide developers—particularly web developers and open-source programmers—with a streamlined method to operate Linux tools and workflows directly on Windows. This innovation has also been well-received by system administrators who can now manage Linux environments on Windows machines more efficiently. By eliminating the need for dual-boot setups or resource-heavy virtual machines, WSL allows users to run Linux applications alongside their Windows software, enhancing the overall development experience.
Microsoft’s efforts in this domain have proven successful. According to StackOverflow’s 2024 developer survey, 16.8% of programmers now utilize WSL as part of their work operating system, surpassing the usage rates of traditional Linux distributions like Debian, Arch, or Red Hat Enterprise Linux (RHEL).
The Evolution of WSL
The journey to this milestone was not without its challenges. The initial version, WSL 1, relied on a compatibility layer to translate Linux system calls for the Windows NT kernel, which resulted in performance limitations. However, the introduction of WSL 2 in 2019 marked a turning point, featuring a full Linux kernel running in a lightweight virtual machine. This upgrade significantly enhanced compatibility and performance, allowing users to run graphical Linux interfaces and applications, not just command-line tools.
With the recent release, Microsoft has made the majority of WSL’s codebase available on GitHub under the MIT License. This includes essential command-line tools such as wsl.exe, wslg.exe, and wslconfig.exe, as well as the WSL service responsible for VM management, distro booting, networking, and file sharing. Additionally, the company has opened up the Linux-side daemons and init processes that manage core functionalities like networking and port forwarding. While some components remain closed source, such as the outdated lxcore.sys, the overall move represents a significant shift in Microsoft’s approach to open-source collaboration.
The decision to open-source WSL has been a long time coming, with the first inquiry about this possibility dating back to 2016. Microsoft acknowledges that the evolution of WSL has been heavily influenced by community contributions, stating, “WSL could never have been what it is today without its community.” Pavan Davuluri, Microsoft’s corporate VP for Windows, noted that the lengthy process was due to substantial architectural changes needed to decouple WSL from the main Windows codebase.
Today, users can access a wide array of popular Linux distributions on WSL, including Fedora, Debian, openSUSE, and Ubuntu, along with more niche options like Arch Linux and Kali Linux. With sufficient resources, users can even run multiple distributions simultaneously alongside their Windows environment.
For those interested in exploring the intricacies of WSL, the WSL GitHub site offers a wealth of information and resources.
