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pyrefly

A high-performance Python type checker and language server providing fast code analysis and IDE integration.

  • Backend
  • Full stack
  • Code quality
  • CLI
  • IDE plugin
  • Windows
  • macOS
  • Linux
  • Runs locally
Open websiteView on GitHub
pyrefly screenshot
Popularity
7.0k Stars
GitHub stars
Recent activity
9/18/2026
Updated in the last 30 days
License
MIT
Permissive

Why it matters

We look beyond stars: what problem it solves, whether it creates real utility, and what makes its approach worth noticing.

Last 90 days

Problem

Static type checking for Python often hits performance bottlenecks in large codebases, leading to slow feedback loops.

Practical value

Significantly reduces type verification time for large projects through high-speed checking and built-in support for major frameworks.

Innovation / differentiation

Achieves processing efficiency far exceeding Mypy and Pyright through low-level optimizations while maintaining compatibility with existing tools.

Leverage potential

Provides a smooth migration path and automated type inference tools, lowering the barrier for switching from existing checkers.

Why now

As Python is increasingly used in large-scale engineering, the demand for high-performance type checking tools is growing.

Community activity

In the last 90 days there were 509 new issues and 591 pull requests; the bounded issue/PR samples include 40 issue authors and 32 PR contributors, with at least 11 releases.

Maintainer responsiveness

The 97-issue window sample had a 80% close rate, and the 99-pull-request sample had a 0% merge rate. Maintainer-comment observations covered only 18% of that issue sample, so response rate and first-response speed are not reported.

32 contributors in PR sampleAt least 11 releasesPR merge rate 0% · 99 sampled in window

Key highlights

  • Lightning-fast type checking processing over 1 million lines per second
  • Full-featured language server with code navigation, completion, and semantic highlighting
  • Built-in support for Pydantic, Django, and pytest frameworks

Quick start

How it is installed, how hard it is, and where to start.

Where it runs

Runs locally

Difficulty

Easy — follow the steps

Runs locally
  1. 01Install the command-line tool using pip.
  2. 02Install the corresponding Pyrefly extension in your IDE.
  3. 03Run the initialization command to configure your project.

Best for

  • Developers who want to try it on their machine

More about it

Pyrefly is a type checker and language server optimized for large-scale Python projects. It delivers millisecond-level feedback in IDEs through high-performance analysis, while providing essential features like code completion and hover information.

The tool integrates with popular editors and includes deep support for frameworks such as Pydantic and Django. It offers a suite of migration and maintenance utilities, allowing users to adopt type checking incrementally using commands like pyrefly init and pyrefly infer.

Sources

Each field shows its status and source — expand to review.

14 · Expand

  • capability tags

    Verified

    code_quality

    Source: admin_cms · cms editor · 8/27/2026

  • editor note

    Verified

    {"en":"Developed by Meta for large-scale codebases like Instagram, Pyrefly excels in type-checking speed. It includes built-in support for frameworks like Pydantic and Django, making it suitable for complex projects migrating from Mypy or Pyright.","zh":"Pyrefly 由 Meta 开发并用于 Instagram 等大规模代码库，其核心优势在于极高的类型检查速度。它内置了对 Pydantic、Django 等框架的深度支持，适合从 Mypy 或 Pyright 迁移的复杂项目。"}

    Source: admin_cms · cms editor · 8/27/2026

  • how to use

    Verified

    {"steps":[{"en":"Install the command-line tool using pip.","zh":"通过 pip 安装命令行工具。"},{"en":"Install the corresponding Pyrefly extension in your IDE.","zh":"在 IDE 中安装对应的 Pyrefly 插件。"},{"en":"Run the initialization command to configure your project.","zh":"运行初始化命令以配置项目。"}],"installAt":"local","difficulty":"easy"}

    Source: admin_cms · cms editor · 8/27/2026

  • intro

    Verified

    {"en":"Pyrefly is a type checker and language server optimized for large-scale Python projects. It delivers millisecond-level feedback in IDEs through high-performance analysis, while providing essential features like code completion and hover information.\n\nThe tool integrates with popular editors and includes deep support for frameworks such as Pydantic and Django. It offers a suite of migration and maintenance utilities, allowing users to adopt type checking incrementally using commands like `pyrefly init` and `pyrefly infer`.","zh":"Pyrefly 是一款专为大规模 Python 项目设计的类型检查器与语言服务器。它通过极高的处理性能，在 IDE 中实现毫秒级的实时反馈，并提供代码补全、悬停提示等辅助开发功能。\n\n该工具不仅兼容主流编辑器，还针对 Pydantic、Django 等常用框架进行了深度优化。它提供了一套完整的迁移与维护工具，支持用户通过 `pyrefly init` 和 `pyrefly infer` 等命令逐步引入类型检查。"}

    Source: admin_cms · cms editor · 8/27/2026

  • Latest release

    Verified

    1.3.1

    Source: GitHub API · latest_release=1.3.1 · 9/18/2026

  • License

    Verified

    MIT

    Source: GitHub API · license.spdx_id=MIT · 9/18/2026

  • needs api key

    Verified

    No

    Source: admin_cms · cms editor · 8/27/2026

  • One-liner

    Verified

    {"en":"A high-performance Python type checker and language server providing fast code analysis and IDE integration.","zh":"一款高性能 Python 类型检查器与语言服务器，支持快速代码分析及主流 IDE 集成。"}

    Source: admin_cms · cms editor · 8/27/2026

  • Platforms

    Verified

    windows, macos, linux

    Source: admin_cms · cms editor · 8/27/2026

  • Category hint

    Inferred from materials

    developer-tools

    Source: Project README · hint=developer-tools · 8/17/2026

  • product forms

    Verified

    cli, ide_plugin

    Source: admin_cms · cms editor · 8/27/2026

  • role tags

    Verified

    backend, fullstack

    Source: admin_cms · cms editor · 8/27/2026

  • supports local

    Verified

    Yes

    Source: admin_cms · cms editor · 8/27/2026

  • supports self host

    Verified

    No

    Source: admin_cms · cms editor · 8/27/2026

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