Microsoft has designated Rust as a "Tier 1" internal programming language, putting it on equal footing with C++, C# and TypeScript for in-house development. The move, announced by principal engineer Victor Ciura at RustConf in Montréal, formalises the tooling and processes needed to support Rust throughout the software development lifecycle and reflects the language's growing role in tackling memory-safety flaws that have long plagued Windows and other Microsoft products.

Rust already features in more than 100 Microsoft repositories, underpinning services such as Outlook, Word, Excel, OneDrive and SharePoint via the company's Oxidizer toolkit, as well as parts of the Copilot stack. Microsoft has also built a custom compiler backend, rustc_codegen_utc, to integrate Rust directly with its MSVC Windows toolchain. The push comes as roughly 70 percent of Windows CVEs stem from memory-related bugs, according to Azure CTO Mark Russinovich, though engineers still face challenges managing "unsafe" interactions where Rust code meets legacy C++ memory allocations.