- https://github.com/astral-sh/ty/releases/tag/0.0.2
- https://astral.sh/blog/ty (ty: An extremely fast Python type checker and LSP)
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TL;DR: ty is an extremely fast Python type checker and language server, written in Rust, and designed as an alternative to tools like mypy, Pyright, and Pylance.
Today (2025-12-16), we're announcing the Beta release of ty.
We now use ty exclusively in our own projects and are ready to recommend it to motivated users for production use.
At Astral, we build high-performance developer tools for the Python ecosystem. We're best known for uv, our Python package manager, and Ruff, our linter and formatter.
Today (2025-12-16), , we're announcing the Beta release of the next tool in the Astral toolchain: ty, an extremely fast Python type checker and language server, written in Rust.
You can install ty today with uv tool install ty@latest
Like Ruff and uv, ty's implementation was grounded in some of our core product principles:
- 1. An obsessive focus on performance. Without caching, ty is consistently between 10x and 60x faster than mypy and Pyright. When run in an editor, the gap is even more dramatic. As an example, after editing a load-bearing file in the PyTorch repository, ty recomputes diagnostics in 4.7ms: 80x faster than Pyright (386ms) and 500x faster than Pyrefly (2.38 seconds). ty is very fast!
- 2 Correct, pragmatic, and ergonomic. With features like first-class intersection types, advanced type narrowing, and sophisticated reachability analysis, ty pushes forward the state of the art in Python type checking, providing more accurate feedback and avoiding assumptions about user intent that often lead to false positives. Our goal with ty is not only to build a faster type checker; we want to build a better type checker, and one that balances correctness with a deep focus on the end-user experience.
3. Built in the open. ty was built by our core team alongside dozens of active contributors under the MIT license, and the same goes for our editor extensions. You can run ty anywhere that you write Python (including in the browser).
Even compared to other Rust-based language servers like Pyrefly, ty can run orders of magnitude faster when performing incremental updates on large projects.
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