Meta Open Source

⚡️OSS Project Spotlight⚡️

Lexical is an extensible text editor framework designed for reliability, accessibility, and performance. It provides a powerful, framework-agnostic engine for building sophisticated text editing experiences on both the web and iOS.

Learn more: https://lexical.dev/

4 Pyrefly Type Narrowing Patterns that make Type Checking more Intuitive | Pyrefly Learn about 4 ways Pyrefly narrows types, reducing the need to explicitly cast in your code.

New Meta Open Source Content 🔎

Four type-narrowing patterns that make Python type checking more intuitive. 🐍✨
From tuple length narrowing to hasattr guards, see how Pyrefly helps reduce the need for explicit casts in your code.

Learn more here: https://pyrefly.org/blog/type-narrowing/

Infer Static Analyzer | Infer | Infer A tool to detect bugs in Java and C/C++/Objective-C code before it ships

🔎 Meta Open Source 101🔎

Want to catch null pointer exceptions and resource leaks before they crash your app? Use Infer, a static analyzer that detects complex bugs in Java, C++, and Objective-C.

Learn more at https://fbinfer.com/

IGListKit A data-driven UICollectionView framework for building fast and flexible lists.

⚡️OSS Project Spotlight⚡️

IGListKit is a data-driven UICollectionView framework for building fast lists on iOS. It features a decoupled diffing algorithm that handles updates automatically, eliminating reloadData or performBatchUpdates.

Learn more: https://instagram.github.io/IGListKit/

Python Typing Survey 2025: Code Quality and Flexibility As Top Reasons for Typing Adoption The 2025 Typed Python Survey, conducted by contributors from JetBrains, Meta, and the broader Python typing community, offers a comprehensive look at the current state of Python’s type system and d…

Python typing is trending — and the community has spoken! 📊

From improved readability to better tooling support, see what developers love (and struggle with) in 2025:

https://engineering.fb.com/2025/12/22/developer-tools/python-typing-survey-2025-code-quality-flexibility-typing-adoption/

YouTube video by Meta Open Source How Pyrefly Works with Pydantic (v1 experimental support)

🔎 Check out our new video on Pyrefly’s Pydantic support

Pyrefly currently offers experimental support for Pydantic, bringing improved static type checking and IDE integration to your data models.

▶️ Watch the video: youtu.be/zXYpSQB57YI
#Python #TypeChecking #OpenSource

Souper-Model: How Simple Arithmetic Unlocks State-of-the-Art LLM Performance | Research - AI at Meta Large Language Models (LLMs) have demonstrated remarkable capabilities across diverse domains, but their training remains resource- and time-intensive,...

🚀 New from Meta AI Research: Souper-Model! By smartly averaging multiple model weights using a method called SoCE (Soup Of Category Experts), the team achieved strong performance without retraining a whole new model.

Read more here: https://loom.ly/bSbrL70

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. - YouTube

Announcing Pyrefly is now in Beta 🎉

Pyrefly is a super fast, open source language server and typechecker for Python. We’ve been working closely with our open source community to improve performance, add new features and address bugs.

Learn more: https://youtu.be/4o0RLJJ-FAo

Efficient Optimization With Ax, an Open Platform for Adaptive Experimentation Efficient Optimization With Ax, an Open Platform for Adaptive Experimentation

🚀 New Blog Post Alert 🚀

Ax, our OS adaptive experimentation platform, uses machine learning to automate and optimize complex experiments. Discover real-world applications of AX across AI, GenAI, infrastructure and even physical engineering.

Learn more: https://loom.ly/Djv-f8k

GitHub - facebookincubator/below: A time traveling resource monitor for modern Linux systems A time traveling resource monitor for modern Linux systems - facebookincubator/below

⚡️OSS Project Spotlight⚡️

Below is a powerful resource monitoring tool for Linux that provides deep insights into system performance, including CPU, memory, I/O, and more — all from an intuitive terminal interface.

Learn more: https://github.com/facebookincubator/below

StyleX: A Styling Library for CSS at Scale StyleX is Meta’s styling system for large-scale applications. It combines the ergonomics of CSS-in-JS with the performance of static CSS, generating collision-free atomic CSS while allowing for expressive, type-safe style authoring.

🚀 StyleX: Meta’s Open Source Styling Library for CSS at Scale!

StyleX is the styling system that combines the best of CSS-in-JS ergonomics with the performance of static CSS—making styling expressive, type-safe, and lightning fast.

Link: https://loom.ly/IEnQjTY

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. - YouTube

Did you know that 63% of AI training models today are built on @PyTorch? When Meta first released the framework, we wanted to support developer experiences for AI researchers. Today, PyTorch helps accelerate the path to AI productization around the world: https://youtu.be/g__HkxDEvCg

Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on YouTube. - YouTube

🚀 New Podcast Episode Alert!

Are you passionate about Python typing or developer experience? Check out the latest episode of @talkpython.fm featuring Pyrefly, Meta’s blazing-fast type checker for Python:
https://www.youtube.com/watch?v=P4RKxl_giH4&t=2s

Branching in a Sapling Monorepo Sapling is a scalable, user-friendly, and open-source source control system that powers Meta’s monorepo. As discussed at the GitMerge 2024 conference session on branching, designing and imple…

🚀 New on the Meta Engineering blog: Branching in a Sapling Monorepo

Discover how Meta solved the tradeoffs between scalability and dev experience by introducing directory branching alongside full-repo branching in Sapling.

Read more here: https://loom.ly/GgxCxto

Captum · Model Interpretability for PyTorch Model Interpretability for PyTorch

⚡️OSS Project Spotlight⚡️

Captum is an open source library from Meta for model interpretability in PyTorch. It helps developers understand and visualize the decisions made by deep learning models using attribution methods like Integrated Gradients and DeepLIFT.

Learn more: https://captum.ai/

Introducing the React Foundation: The New Home for React & React Native Meta open-sourced React over a decade ago to help developers build better user experiences. Since then, React has grown into one of the world’s most popular open source projects, powering over 50 m…

🚀 Big news! Today marks the formation of the React Foundation — a new home for React, React Native, JSX, and the broader React ecosystem.

Let’s celebrate a new chapter for React and the open web!

🔗 Read more: https://loom.ly/UrW8eeI

#React #OpenSource #WebDev #ReactNative

Introducing OpenZL: An Open Source Format-Aware Compression Framework Introducing OpenZL: An Open Source Format-Aware Compression Framework

🚀 Introducing OpenZL, a new #opensource, format-aware compression framework!

It uses a unique “graph model” for compression, enabling modular, high-performance codecs and a universal decoder - perfect for structured data at scale

Link: https://loom.ly/z09xoNw

#DataCompression

Give your Python IDE a Glow-Up with Pyrefly | Pyrefly Learn how Pyrefly's language server capabilities can help you navigate large Python codebases with ease.

How do you make sure your IDE works smoothly when you have more than 20 million lines of python code? 🤔

For devs at Instagram the answer is to use the Pyrefly VSCode extension 👩🏼‍💻

Read our blog about how Pyrefly improves your experience: https://pyrefly.org/blog/2025/09/15/ide-extension/

🔎 Meta Open Source 101🔎

Meet Sapling, Meta’s next-gen source-control system. It’s Git-compatible but designed for massive repos and lightning-fast operations, even at scale. Perfect if you need speed and a smooth developer experience.

Learn more 👉 https://sapling-scm.com