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Introduction

LangChain is a framework for developing applications powered by large language models (LLMs).

LangChain simplifies every stage of the LLM application lifecycle:

Diagram outlining the hierarchical organization of the LangChain framework, displaying the interconnected parts across multiple layers.Diagram outlining the hierarchical organization of the LangChain framework, displaying the interconnected parts across multiple layers.

Concretely, the framework consists of the following open-source libraries:

  • langchain-core: Base abstractions and LangChain Expression Language.
  • langchain-community: Third party integrations.
    • Partner packages (e.g. langchain-openai, langchain-anthropic, etc.): Some integrations have been further split into their own lightweight packages that only depend on langchain-core.
  • langchain: Chains, agents, and retrieval strategies that make up an application's cognitive architecture.
  • LangGraph: Build robust and stateful multi-actor applications with LLMs by modeling steps as edges and nodes in a graph.
  • LangServe: Deploy LangChain chains as REST APIs.
  • LangSmith: A developer platform that lets you debug, test, evaluate, and monitor LLM applications.
note

These docs focus on the Python LangChain library. Head here for docs on the JavaScript LangChain library.

Tutorials​

If you're looking to build something specific or are more of a hands-on learner, check out our tutorials. This is the best place to get started.

These are the best ones to get started with:

Explore the full list of tutorials here.

How-to guides​

Here you’ll find short answers to “How do I….?” types of questions. These how-to guides don’t cover topics in depth – you’ll find that material in the Tutorials and the API Reference. However, these guides will help you quickly accomplish common tasks.

Conceptual guide​

Introductions to all the key parts of LangChain you’ll need to know! Here you'll find high level explanations of all LangChain concepts.

API reference​

Head to the reference section for full documentation of all classes and methods in the LangChain Python packages.

Ecosystem​

🦜🛠️ LangSmith​

Trace and evaluate your language model applications and intelligent agents to help you move from prototype to production.

🦜🕸️ LangGraph​

Build stateful, multi-actor applications with LLMs, built on top of (and intended to be used with) LangChain primitives.

🦜🏓 LangServe​

Deploy LangChain runnables and chains as REST APIs.

Additional resources​

Security​

Read up on our Security best practices to make sure you're developing safely with LangChain.

Integrations​

LangChain is part of a rich ecosystem of tools that integrate with our framework and build on top of it. Check out our growing list of integrations.

Contributing​

Check out the developer's guide for guidelines on contributing and help getting your dev environment set up.

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