Rust becomes a Tier-1 language inside Microsoft

What Tier-1 means

Microsoft now counts Rust among C++, C# and TypeScript as one of the best-supported languages for internal development. The classification, described in a guest post published by the Rust Foundation, is an engineering status rather than a marketing label: a “paved path” from local development to production, covering secure toolchain builds, developer tooling, quality workflows, deep platform integration and compliance with the SDL requirements Microsoft software must meet.

The company’s history with the language runs from Azure CTO Mark Russinovich’s public statements about native code to millions of dollars invested in supporting the Rust Project. Today Rust appears in firmware and drivers, kernels and hypervisors, microservices and applications.

rustc_codegen_utc explained

The centre of the post is a compiler component: rustc_codegen_utc, an alternative code-generation backend for rustc in the same architectural family as rustc_codegen_llvm, rustc_codegen_gcc and rustc_codegen_cranelift. It plugs into the same backend interface and connects rustc’s shared compiler machinery to the MSVC backend — Microsoft’s native compiler for Windows, also known as UTC.

The goal is a unified code-generation platform for Rust and C++ on Windows. MSVC and Windows have co-evolved for decades, and Microsoft argues that new security features, diagnostics and servicing technologies should reach both languages instead of requiring a parallel implementation of every Windows-specific capability.

What the backend unlocks

According to the post, connecting rustc to that backend gives Rust high compatibility with the Windows tooling ecosystem and ABI, binary hardening and code-security features, post-link compliance, analysis and servicing including Hotpatch, seamless Rust/C++ interop for hybrid projects, cross-language inlining and Sample Profile Guided Optimization, debugging and crash-dump analysis, and profiling, diagnostics and coverage.

Interop is only half about code generation: FFI contracts, bindings, differences in language semantics and build systems remain open problems, which the Rust Foundation’s Interoperability Initiative is tracking.

Production use since early 2026

rustc_codegen_utc has been production-ready since early 2026 and has been self-hosted since Rust 1.90. More than 100 Microsoft project repositories already build with it, and the rollout continues each week as more repositories adopt it.

On other platforms, a hybrid Rust/C++ project that builds its C++ with Clang can already reach the same LLVM code-generation platform; the new backend is meant to create the equivalent shared-backend opportunity on Windows-native projects where MSVC is the platform compiler.