Pyrefly
Hacker ApprovedRanked 4 of 6 Python type checkers by recommenders
People recommend it for speed, low memory use and strict type checking. Main caveat: its editor extension can change config files without asking.
People recommend it for speed, low memory use and strict type checking. Main caveat: its editor extension can change config files without asking.
36 people gave an opinion
- recommend it
- 28
- criticize it
- 8
- approval share
- 78%
Recommended in 8 of 13 months
- November 2025: recommended
- December 2025: recommended
- January 2026: not recommended
- February 2026: not recommended
- March 2026: recommended
- April 2026: not recommended
- May 2026: recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: not recommended
- September 2026: recommended
- October 2026: recommended
- November 2026: not recommended (month in progress)
Owned for 1 month
Median of the 3 owners who said how long they have had it.
Each square is one year.
Why it carries the badge
- 28 people recommend itNeeds 10 or more, met.
- 3.5 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 8 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Faster than other checkers
“we are quite a bit faster than pyright (almost 10x avg) and use far less memory (almost half)”
Comment from 15 May 2026 in “Pyrefly v1.0.0 is here (Type Checker / Language Server for Python) [video]” “rust-based tools (ty, pyrefly) have popped up, running sub-second.”
Comment from 6 Jun 2026 in “Show HN: Typedframes – Pandas/polars column name checking at lint time” “The reason I prefer pyrefly over mypy is mostly because of speed.”
Comment from 17 Mar 2026 in “Comparing Python Type Checkers: Typing Spec Conformance” - Comment from 25 Oct 2026 in “Bringing uv and ty together”
- Comment from 25 Oct 2026 in “Bringing uv and ty together”
- Comment from 25 Sep 2026 in “Topcoat is pushing the boundary of server applications with Rust”
Works well with uv and ruff
“with that combination, has roughly the same agent ergonomics as Go and lower token count due to higher abstraction level”
Comment from 8 Jul 2026 in “Why TypeScript 7.0 Was Rewritten in Go” “Python has uv, ruff and Pyrefly, and with that combination, has roughly the same agent ergonomics as Go”
Comment from 8 Jul 2026 in “Why TypeScript 7.0 Was Rewritten in Go” “UV, Ruff and Pyrefy and you're set”
Comment from 11 Jul 2026 in “Scarf has moved away from Haskell” Has the features people want
“the Pyrefly implementation seems to have everything I'd like”
Comment from 13 May 2026 in “Pyrefly v1.0.0 is here (Type Checker / Language Server for Python) [video]” “pyrefly has everything and is faster than ty”
Comment from 25 Oct 2026 in “Bringing uv and ty together” “everything I wanted from ty”
Comment from 24 Oct 2026 in “Bringing uv and ty together” Strong type checking
“Pyrefly has much better checks IME (at least with strict mode)”
Comment from 24 Oct 2026 in “Bringing uv and ty together” “purely on a type checking front, it's excellent”
Comment from 24 Oct 2026 in “Bringing uv and ty together”
What people warn about
Each mark is one comment
Crash bugs in some releases
“I've been using Pyrefly and loving it compared to Pyright, but they recently shipped some updates with crash bugs”
Comment from 17 Dec 2025 in “Announcing the Beta release of ty” “they recently shipped some updates with crash bugs that forced me to pin to a previous version”
Comment from 16 Dec 2025 in “Announcing the Beta release of ty” Changes settings without asking
“it should definitely be documented and undone on uninstall but the action itself is reasonable”
Comment from 2 May 2026 in “Meta's Pyrefly sabotages competing Python extensions without telling you” “Writing to global settings and leaving the mess behind after uninstall is not the same thing.”
Comment from 2 May 2026 in “Meta's Pyrefly sabotages competing Python extensions without telling you” “Could they not gate this behind a notification on install?”
Comment from 2 May 2026 in “Meta's Pyrefly sabotages competing Python extensions without telling you” - Comment from 2 May 2026 in “Meta's Pyrefly sabotages competing Python extensions without telling you”
Can use a lot of memory
“It’s a memory hog! The other day it was using 2.5GB of RAM.”
Comment from 13 May 2026 in “Pyrefly v1.0 is here (fast type checker and language server for Python)” “It's a huge memory hog. The other day it was using 2.5GB!”
Comment from 13 May 2026 in “Pyrefly v1.0.0 is here (Type Checker / Language Server for Python) [video]”
Other Python type checkers people recommend
The four most recommended other Python type checkers, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| ty Python type checker | 74 | 26 | 74% | 11 | — | Approved |
| mypy | 34 | 14 | 71% | 10 | — | Approved |
| Pyright | 31 | 16 | 66% | 11 | — | — |
| PyreflyThis page | 28 | 8 | 78% | 8 | 1 mo3 owners | Approved |
| basedpyright | 9 | 7 | 56% | 7 | — | — |
What people said
40 of the 44 comments that mention it, newest first. Each links to the original comment.
“Pyrefly and Zuban are faster. Pyrefly and Zuban use less memory.”
“pyrefly has everything and is faster than ty”
“everything I wanted from ty”
“purely on a type checking front, it's excellent”
“Pyrefly has much better checks IME (at least with strict mode)”
“pyrefly seems to me to be the furthest along with support for many common libraries”
“Pyrefly is better than ty for my use cases.”
“If you want speed and strict conformance, Pyrefly and Zuban are better.”
“a very fast type checker (Pyrefly)”
“vscod(ium) with pyrefly LSP is miles better than Pycharm today”
“UV, Ruff and Pyrefy and you're set”
“Python has uv, ruff and Pyrefly, and with that combination, has roughly the same agent ergonomics as Go”
“with that combination, has roughly the same agent ergonomics as Go and lower token count due to higher abstraction level”
“rust-based tools (ty, pyrefly) have popped up, running sub-second.”
“I'm very excited that Pyrefly is addressing a problem I have”
“which makes it simpler to reason about them when you're writing the code and catch bugs”
“we are quite a bit faster than pyright (almost 10x avg) and use far less memory (almost half)”
“the migration was painless”
“the Pyrefly implementation seems to have everything I'd like”
“It’s a memory hog! The other day it was using 2.5GB of RAM.”
“It's a huge memory hog. The other day it was using 2.5GB!”
“What a happy surprise to get a 1.0 as fresh delivery straight in to my project.”
“We're excited to announce general availability today!”
“Writing to global settings and leaving the mess behind after uninstall is not the same thing.”
“Don't touch my config without my consent.”
“it even says it in the initial installation instructions and gives a clear reason why it interferes with other language servers”
“it should definitely be documented and undone on uninstall but the action itself is reasonable”
“That's a convenient thing to do: if user installs Pyrefly, they probably want to use Pyrefly.”
“Could they not gate this behind a notification on install?”
“it most likely has added "features" you may not expect”
“there are competing LSPs of reasonable quality now”
“The reason I prefer pyrefly over mypy is mostly because of speed.”
“That’s hardly 300 external tools.”
“If you're starting a new project, there's no reason you shouldn't.”
“The most annoying thing was Pyrefly's lack of exhaustive pattern matching for StrEnum and Literal[...]”
“I've been using Pyrefly and loving it compared to Pyright, but they recently shipped some updates with crash bugs”
“The Pyrefly extension needed a config tweak to work.”
“they recently shipped some updates with crash bugs that forced me to pin to a previous version”
“pyrefly which also seems great”
“new type checking solutions like pyrefly aren't there yet for my use cases.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.