Linux: Microsoft WSL’s Decade-Long Journey to Open Source
It took Microsoft nearly a decade, but the company has officially open sourced the Windows Subsystem for Linux (WSL). The milestone was first shared publicly by Microsoft’s senior product manager Craig Loewen and principal product manager lead Clint Rutkas during Canonical’s Ubuntu 25.10 Summit in London.
The Origins of WSL
WSL’s development traces back to 2010 with a project code-named Astoria, or Windows Bridge for Android. The idea behind Project Astoria was to allow Android apps to run on Windows Phone through a translation layer built into the Windows 10 Mobile kernel.
“Since you’re unlikely to have a working Windows Phone in your pocket, you know how that turned out.”
Although Project Astoria was ultimately abandoned, its technical foundation laid the groundwork for what would become WSL. The experimental prototype could translate Linux system calls into Windows NT kernel calls—a crucial breakthrough that enabled compatibility between the two platforms.
Building on Collaboration
In 2016, Microsoft, with collaboration from Canonical, launched Bash and Ubuntu on Windows. This early version of WSL recompiled Cygwin’s open source utilities to run natively on Windows, marking the beginning of a new era of Linux and Windows cooperation.
A Broader Open Source Commitment
The decision to finally open source WSL reflects Microsoft’s continuing integration with the open source ecosystem. What started as a compatibility experiment now stands as a symbol of Microsoft’s evolving relationship with Linux and its developer community.
Author’s summary: Microsoft spent nearly ten years developing WSL, transforming it from a failed mobile bridge into a fully open-sourced platform that united Windows and Linux development.