How Microsoft Is Rewriting the Windows 11 Kernel with Rust for Safer, Faster Performance

Recently Microsoft announced that it is rewriting parts of the Windows 11 kernel using the Rust programming language, replacing previously C++ code with roughly 36,000 new lines that have passed boot tests.

Azure Cloud CTO Mark Russinovich confirmed that the Rust‑based Win32k.sys kernel‑mode driver has been ported to the Windows 11 Insider preview.

He tweeted that insiders can now “taste the flavor of Rust” inside the Windows kernel.

Win32k.sys handles the graphical device interface (GUI) and window management on Windows.

Rust’s advantages—high memory safety—have eliminated many unsafe subroutines in the kernel, while its concise and efficient code has caused no performance loss for Office applications, and in some scenarios it even runs faster than the original C++.

The latest builds show additional Rust compilation files via the command line.

Current Windows 11 Insider builds include Canary Build 25357, Dev Build 23451, and Release Preview Build 22621.1776.

Microsoft first revealed its plan to replace parts of the Windows kernel with Rust at the BlueHat IL security conference in mid‑March, where VP David Weston described the effort as part of a “positive and meaningful pursuit of memory safety.”

Within a month, Rust code has already appeared in the core of Windows 11, demonstrating a development pace comparable to open‑source projects.