SUMMARYMicrosoft has made Rust a Tier One language for internal development, placing it alongside C++, C#, and TypeScript as a fully supported option. The company says Rust is used in more than 100 project repositories and has helped power Microsoft 365 core services as well as parts of the Copilot stack. At RustConf in Montréal, Microsoft engineers also pointed to Rust’s role in reducing memory-safety issues that account for many Windows security vulnerabilities.
The Register reports:
When Microsoft's developers and engineers sit down to code, they can now choose to work in Rust, which Redmond has added to its list of canonical languages. "Rust now is a Tier One language at Microsoft, and that just means that it sits among C++, C# and TypeScript as the best supported languages for internal development in the company," explained Victor Ciura, Microsoft principal engineer for the Rust tooling team, during a keynote talk today at this year's annual RustConf, being held this week in Montréal. Ciura said Microsoft has "paved a path" of tools and processes that support local Rust development across the entire software development lifecycle.
Rust is no stranger at Microsoft and is already present in over 100 Microsoft project repositories. The company has built Oxidizer, a set of crates to build scalable services in Rust, which have been used to build and refine the Microsoft 365 core services such as Outlook, Word, Excel, OneDrive, and SharePoint. The Copilot tech stack also owes quite a bit to Rust... [C]ompany engineers built rustc_codegen_utc, a custom Rust compiler code-generation backend that wires the rustc compiler directly into the Microsoft Visual C++ internal toolchain for Windows... "The result is a unified code generation platform for Rust and C++ on Windows" [Ciura wrote in a blog post, noting that more than 100 Microsoft project repositories now build with rustc_codegen_utc.]
Still, Redmond running towards Rust is a welcome development. In his 2025 RustConf keynote, Microsoft Azure CTO Mark Russinovich noted that ~70 percent of Windows CVEs are memory issues. "One of the things that I realized a long time ago is that no matter how much we really want to make C and C++ better, we can't make it as good as what Rust starts with," he said.