Windows Subsystem for Linux is now open source. Read that again, and again. Announced at the Build 2025 developer conference, this marks the closing of a request that was submitted nearly nine years ago.

One thing to remember is that this is not the Microsoft of old, so releasing something as open source shouldn't be that big of a deal, but WSL is a bit different because it directly involves Linux. The code for WSL is now available on GitHub (downloaded as either a .zip or .tar.gz file).

Before you get too excited (you knew this was coming), Microsoft didn't open source the entire WSL code. What you will find is the WSL command-line tools (like wsl.exe and wslconfig.exe), as well as the WSL service, which is responsible for several tasks (such as virtual machine management, booting distributions, networking, Linux init and daemon processes, and file sharing).

The newly opened bits are in addition to those that were already open, such as microsoft/wslg (for Wayland support and X server scenarios) and microsoft/WSL2-Linux-Kernel (the source for the Linux kernel used in WSL 2).

The WSL components that are still proprietary are lxcore.sys (the kernel-side driver that powers WSL 1), p9rdr.sys, and p9np.dll (both of which run the \\wsl.localhost filesystem).