Google Replaces pytype With Pyrefly: Which Type Checker in 2026
Originally published at WowHow Google has made Pyrefly, Meta's Rust-based Python type checker, its type checker across the company and is dropping pytype, and if your CI still runs pytype you are on a tool whose own README says Python 3.12 is the last supported version. Google's announcement dated 6 October 2026 reports Pyrefly as "an order of magnitude faster than Pytype" on its internal benchmarks and scoring roughly 97% on the official typing conformance suite [1] . The pytype repository was archived on 3 September 2026 [2] . Below: what Google actually said, a four-way comparison of mypy, Pyright, Pyrefly and ty, a bug that a sound checker catches and a lenient one lets through, and a migration path you can run this week. TL;DR pytype is finished: its README names 3.12 as the last supported Python version and the repo is archived. Plan a move now, not when your next Python upgrade breaks it. Pyrefly is the closest drop-in for pytype and mypy users who wan...