ty is the third major tool from Astral, completing their vision of rebuilding Python's core development toolchain in Rust for maximum performance. Where Ruff replaced flake8 and black for linting and formatting, and uv replaced pip and virtualenv for package management, ty targets mypy and pyright for type checking. The result is a type checker that can process large codebases in seconds rather than minutes, with full support for Python's type system including generics, protocols, and the latest PEP 695 syntax.
The type checker performs whole-program inference, understanding type narrowing through control flow, isinstance checks, and pattern matching. It integrates with existing type stubs from typeshed and supports inline type: ignore comments for gradual adoption. ty outputs clear, actionable error messages with code snippets and fix suggestions, following the same developer experience philosophy that made Ruff popular. Configuration lives in pyproject.toml alongside Ruff and uv settings.
Despite being relatively new, ty has already accumulated over 18,000 GitHub stars, reflecting strong developer demand for faster Python tooling. It is distributed under the MIT license and installs as a single binary with zero Python dependencies. For teams already using Ruff and uv, ty provides the final piece of a coherent, high-performance Python development stack that eliminates the overhead of managing multiple slow Python-based tools.
