Microsoft Makes Rust a Tier-1 Language, Next to C++ and C#

Microsoft has designated Rust a tier-1 language for internal development, placing it alongside C++, C# and TypeScript, Victor Ciura, a principal engineer on Microsoft's Rust tooling team, wrote in a guest post published on the Rust Foundation's site Thursday.

Ciura said tier-1 status means Rust developers at Microsoft now get, in his words, "a paved path from local development to production: secure toolchain builds, productive developer tooling, quality workflows, deep platform integration," and compliance with the company's Security Development Lifecycle, the internal review process Microsoft software must pass before it ships.

What rustc_codegen_utc does

The backend behind the change is rustc_codegen_utc, an alternative code generator for the Rust compiler that Ciura said has been production-ready since early 2026 and self-hosted, meaning it compiles its own source code, since Rust 1.90. It joins a small family of alternative Rust code generators alongside rustc_codegen_llvm, the default, and rustc_codegen_gcc, a GCC-based backend maintained outside Microsoft. Rather than routing through LLVM, rustc_codegen_utc connects rustc directly to the same native toolchain Microsoft's C++ compiler, MSVC, already uses on Windows, which Ciura said lets Rust draw on platform-specific compiler work built up over decades without waiting for the LLVM project to add it separately.

How many repositories use it

More than 100 Microsoft project repositories build with rustc_codegen_utc today, Ciura wrote, with more added each week. He said Microsoft has invested "millions of dollars" in the Rust Project since Azure Chief Technology Officer Mark Russinovich set out the company's native-code strategy, without giving a total figure or the date that spending began.

What the post leaves out

Ciura's post does not name which products beyond the 100-plus repositories now build with the new backend, does not say how large the Rust tooling team is, and does not address the Windows kernel specifically. A separate Microsoft effort, led by distinguished engineer Galen Hunt, has pursued a public goal of removing C and C++ from Microsoft's codebase by 2030; Ciura's post does not mention that initiative or say whether the two efforts are coordinated.

Microsoft has been shipping Rust in specific components for at least a year before Thursday's announcement. Direct Write Core, part of Windows' text-rendering stack, and Mu, an open-source UEFI implementation, are both written in Rust, Ciura said in an April 2025 interview on the corrode.dev podcast, an independent Rust consultancy's show that also covers Rust in Microsoft's Azure Cloud HSM and its integration work with Hyper-V.

The pattern of low-level rewrites reaching production is not confined to Microsoft. Two developers separately ported the GNU Radio signal-processing toolkit to the browser via WebAssembly, and a cluster of newer libraries has tried to bolt durable execution onto Postgres rather than build a bespoke coordination layer, in both cases choosing to rebuild a lower layer rather than patch around its limits, the same trade-off Ciura's post frames as the reason for a second Rust compiler backend instead of waiting on changes to LLVM.

What is still open

Microsoft has not said whether tier-1 status changes hiring for the Rust tooling team, whether it extends to Windows itself rather than the DevDiv organization Ciura works in, or when the count of 100-plus repositories was last checked.