Why Microsoft Open‑Sourced WSL and What It Means for Developers

At the Microsoft Build 2025 conference, Microsoft announced that the Windows Subsystem for Linux (WSL) is now officially open‑source.

On May 20, Microsoft declared that the source code for WSL is publicly available for community contributions.

Since its introduction for Windows 10 nearly nine years ago, Microsoft has continuously worked to open‑source the functionality that enables a Linux environment within Windows.

WSL consists of several distributed components, some running directly on Windows and others inside the WSL 2 virtual machine. The main technical areas are:

User‑mode components that manage Linux distributions, file systems, and process scheduling.

Kernel‑mode components, including the Linux kernel in WSL 2 and the drivers that interact with the Windows kernel.

Virtual‑machine management handling the start, operation, and shutdown of the WSL 2 VM.

Network and display support providing the same networking environment and graphical application capabilities as the host.

WSL Architecture Overview

WSL was first announced at the 2016 Microsoft BUILD conference and shipped with the Windows 10 anniversary update. The initial version, later called “WSL 1,” relied on the pico process provider lxcore.sys to run ELF binaries natively and implement Linux system calls inside the Windows kernel.

To achieve better compatibility with native Linux, WSL 2 was introduced in 2019, featuring a real Linux kernel and delivering significant performance and compatibility improvements.

The WSL community has grown steadily, adding features such as GPU support, graphical application support via WSLg, and systemd integration. In July 2021, Microsoft separated WSL from the Windows codebase and released it as an independent package in the Microsoft Store, initially for Windows 11 preview.

In November 2022, WSL 1.0.0 was released, supporting Windows 10 and marking the first stable version of the standalone package. Subsequent development led to the milestone release of WSL 2.0.0, introducing features like image networking, DNS tunneling, Session 0 support, proxy support, and firewall integration.

The latest version, WSL 2.5.7, has accumulated nine years of GitHub updates covering numerous enhancements and new capabilities.

Windows CEO Pavan Davuluri emphasized that open‑sourcing WSL fulfills a long‑standing developer request, allowing the project to be rebuilt, contributed to, and integrated at scale within Windows.

WSL’s source code is now available on GitHub ( https://github.com/microsoft/WSL ), enabling developers to download, build, fix bugs, and add new features.

Davuluri expects developers to leverage the open‑source project to improve WSL performance and integrate it more deeply with Linux services.

Microsoft’s open‑source move marks a significant milestone for WSL, originally launched in 2016 as part of the Windows 10 anniversary update, and reflects the company’s ambition to make Windows a premier development platform.