2025-09-19 –, Main stage
Pyrefly is a Python type checker built to provide a fast type checking experience, enabling developers to write better code with confidence. It brings an IDE experience powering type hints and code navigation on a new type checking engine that scales to large codebases.
We started working on Pyrefly a little under a year ago, to make a type checker that stays fast on Meta's vast Python codebase, and can be the foundation for more than just checking of Python types.
We'll show how fast Pyrefly is, and why that's essential to power great IDE experiences. Then we'll walk through a few basic examples of how using a type checker is beneficial, sometimes even for 100% untyped code!
By the end you'll learn how to start using Pyrefly for your own code.
Basic
Currently working on Pyrefly @ Meta, focusing on the IDE/LSP.