🎉 Pyrefly v1.0 is now available!
A fast type checker and language server for Python with powerful IDE features
$ pip install pyrefly && pyrefly initScale with Confidence
Type check over 1.85 million lines of code per second.ⓘTested using Meta infrastructure (166 cores, 228 GB RAM)
→Developer Delight
Get lightning fast autocomplete, and catch errors with instant feedback in your favorite editor.
→Verify AI-written Python
Catch type bugs in code your AI agent writes
read the blog →Works where you or your agent writes Python
Performance Comparison
Type checking the PyTorch codebase from scratch.ⓘTested using Macbook
(10 cores: 8 performance + 2 efficiency cores, 32 GB RAM)
(10 cores: 8 performance + 2 efficiency cores, 32 GB RAM)
PyreflyⓘCommand: "pyrefly check"
Pyrefly uses as many threads as possible
Pyrefly uses as many threads as possible
PyrightⓘCommand: "pyright --threads=8"
8 threads yielded the best performance after testing multiple settings
8 threads yielded the best performance after testing multiple settings
MyPyⓘCommand: "dmypy run"