🦜️🔗 LangChain.js

LangChain is a framework for building LLM-powered applications. It helps you chain together interoperable components and third-party integrations to simplify AI application development — all while future-proofing decisions as the underlying technology evolves.

Documentation: To learn more about LangChain, check out the docs.

If you're looking for more advanced customization or agent orchestration, check out LangGraph.js. our framework for building agents and controllable workflows.

[!NOTE] Looking for the Python version? Check out LangChain.

To help you ship LangChain apps to production faster, check out LangSmith. LangSmith is a unified developer platform for building, testing, and monitoring LLM applications.

⚡️ Quick Install

You can use npm, pnpm, or yarn to install LangChain.js

npm install -S langchain
# or
pnpm install langchain
# or
yarn add langchain

🚀 Why use LangChain?

LangChain helps developers build applications powered by LLMs through a standard interface for agents, models, embeddings, vector stores, and more.

Use LangChain for:

• Real-time data augmentation. Easily connect LLMs to diverse data sources and external/internal systems, drawing from LangChain’s vast library of integrations with model providers, tools, vector stores, retrievers, and more.
• Model interoperability. Swap models in and out as your engineering team experiments to find the best choice for your application’s needs. As the industry frontier evolves, adapt quickly — LangChain’s abstractions keep you moving without losing momentum.

📦 LangChain's ecosystem

• LangSmith - Unified developer platform for building, testing, and monitoring LLM applications. With LangSmith, you can debug poor-performing LLM app runs, evaluate agent trajectories, gain visibility in production, and deploy agents with confidence.
• LangGraph - Build agents that can reliably handle complex tasks with LangGraph, our low-level agent orchestration framework. LangGraph offers customizable architecture, long-term memory, and human-in-the-loop workflows — and is trusted in production by companies like LinkedIn, Uber, Klarna, and GitLab.
• Deep Agents - Build sophisticated "deep" agents that go beyond simple tool-calling loops. Deep Agents combines planning tools, sub-agent spawning, file system access, and detailed prompts to handle complex, multi-step tasks — inspired by applications like Claude Code and Deep Research.

🌐 Supported Environments

LangChain.js is written in TypeScript and can be used in:

• Node.js (ESM and CommonJS) - 20.x, 22.x, 24.x
• Cloudflare Workers
• Vercel / Next.js (Browser, Serverless and Edge functions)
• Supabase Edge Functions
• Browser
• Deno
• Bun

📖 Additional Resources

• Getting started: Installation, setting up the environment, simple examples
• Learn: Learn about the core concepts of LangChain.
• LangChain Forum: Connect with the community and share all of your technical questions, ideas, and feedback.
• Chat LangChain: Ask questions & chat with our documentation.

💁 Contributing

As an open-source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infrastructure, or better documentation.

For detailed information on how to contribute, see here.

Please report any security issues or concerns following our security guidelines.