# Comparison of the Two New Typecheckers

At PyCon 2025's Typing Summit, participants saw the first demonstrations of Meta's [Pyrefly](https://pydevtools.com/blog/pyrefly-metas-new-type-checker-for-python.md) and Astral's [ty](https://pydevtools.com/handbook/reference/ty.md), two new Python type checkers with significant speed and analysis improvements.

[Edward Li](https://blog.edward-li.com/) helpfully took notes and provided a right-up.

Here are some takeaways:

* Both tools show substantial speed gains

  * Pyrefly claims up to 1.8 million lines/sec (35× faster than Pyre, 14× faster than MyPy/pyright), while ty benchmarks show it running 2–3× faster than Pyrefly on real-world codebases.

* The tools differ in their approach to type inference

  * Pyrefly pushes aggressive inference, revealing concrete unions even without annotations and catching subtle errors like `None * 2`.
  * ty follows the gradual guarantee, treating unknown types more permissively so type checking never *adds* errors to working code.

> [!WARNING]
> Both tools are still finding their in alpha release and will undergo rapid evolution and feature convergence in the months ahead.

Edward's full notes include benchmarks and examples [on his blog](https://blog.edward-li.com/tech/comparing-pyrefly-vs-ty/).

For a broader comparison including [mypy](https://pydevtools.com/handbook/reference/mypy.md), see [How do mypy, pyright, and ty compare?](https://pydevtools.com/handbook/explanation/how-do-mypy-pyright-and-ty-compare.md). To try ty yourself, see [How to try the ty type checker](https://pydevtools.com/handbook/how-to/how-to-try-the-ty-type-checker.md).