pyrefly
Meta's high-performance Python type checker written in Rust — open-sourced in 2025 as the successor to Pyre, designed for monorepo-scale codebases.
type-checking-frameworksRecently released
59
Hero Score
Popularity
66
Performance
100
Ecosystem
25
Maturity
46
Dev Experience
60
⭐ 6,583 stars⬇ 825.2K downloads/wkFirst release: Feb 2025Last release: May 2026
Async Support: YesPlugin Extensions: GrowingSpeed: Very fastDoc Quality: MediumLearning Curve: Easy
Pros
- • Built by Meta to handle monorepo-scale Python — proven on Instagram's codebase
- • Rust core delivers very fast incremental checking on huge projects
- • Bundled LSP gives the same checks in editor and CI without a second tool
Cons
- • Young open-source project — type semantics and config story are still stabilizing
- • Plugin and framework integration ecosystem is minimal compared to mypy
- • Tutorials and community Q&A are limited outside Meta's own docs