Microsoft Build 2025: WSL becomes open source

At the Build 2025 developer conference, Microsoft announced that the Windows Subsystem for Linux (WSL) is now open source. The code is available in the GitHub repository. In a post on the Windows Developer Blog, Microsoft explains the individual components of WSL and also states which components remain under lock and key – namely the kernel driver for WSL 1 (lxcore.sys) and the file system interface driver (p9rdr.sys and p9np.dll)

Microsoft first presented the Windows subsystem for Linux at Build at the end of March 2016. The first question in the bug tracker of the WSL GitHub repository was: Will this be open source? A good nine years later, the answer is now yes and the issue can be closed. Fittingly, however, successor entries for the kernel driver and the file system driver were posted immediately.

Nine years of Linux on Windows

Shortly after the announcement, WSL was offered for initial testing in the Windows Insider beta test program. With the release of Windows 10 version 1607, also known as the “Anniversary Update” at the time, the first – officially still referred to as “beta” – version was then available in the regular release at the end of July. The subsystem was then part of Windows itself for several years until Microsoft decided to decouple development more from Windows and also offer WSL as a package in the Store to be able to update it more quickly and independently.

Since its initial launch, Microsoft has developed and expanded WSL extensively. In 2019, WSL2 was released, which, unlike the first edition, virtualizes a complete Linux kernel. Since Windows 11, it can also display Linux programs with a GUI directly on the Windows desktop. In the current Windows 11 release 24H2, WSL is no longer integrated into Windows – There is still a wsl.exe, but this is only used to initiate the download of the current version.

(jss)