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Pyrefly vs. ty: Comparing Python’s Two New Rust-Based Type Checkers | Edward Li's Blog

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Earlier this month, two new Rust-based Python type checkers hit the spotlight: pyrefly and ty. Although neither is officially released, they are a welcome change to the Python type checking world, historically dominated by mypy and pylance. While both are open-source and publicly downloadable for quite some time, there have not been any official announcements by Meta nor Astral on their brand new next-generation Python type checkers — until last week. At PyCon 2025, nestled away in a quiet Room 319 at the Typing Summit, we had our first official sneak peek into both of these tools — the team behind them, their goals, visions, and ambitions — and their unique approaches to tackling Python’s typing problems. This blog is a collection of rough notes scribbled during the event, personal conversations with the team, and not-too-thorough experiments that I’ve run myself. As such, some details might be a little blurry. Also, both of these tools are still in early alpha! Please do not use this

Note: I like using em-dashes while writing! Don't worry, this is not written by AI. (context) Earlier this month, two new Rust-based Python type checkers hit the spotlight: pyrefly and ty . Although neither is officially released, they are a welcome change to the Python type checking world, historically dominated by mypy and pyright . While both are open-source and publicly downloadable for quite some time, there have not been any official announcements by Meta nor Astral on their brand new next-generation Python type checkers — until last week . At PyCon 2025 , nestled away in a quiet Room 31

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