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Developer building blocks

LangChain

A toolkit for building AI apps and agents that can use tools and your own data.

Widely used

What it does

LangChain helps developers build applications around AI models, for example a chatbot that answers questions from a company's documents, or an assistant that can search the web and use other tools.

It provides ready-made pieces for connecting AI models to data sources, other software and each other, so developers don't start from scratch.

It was one of the first popular frameworks of the current AI wave and remains one of the most widely downloaded.

Who it's for

Developers building AI-powered products.

Can I use it without coding?

Developers only. A code library for Python (and JavaScript). New to this? Start here.

Can I run it?

Cost
FreeNothing to pay or sign up for.
API key
Not needed

Try it

Using Claude Code, Cursor or another AI coding assistant? Paste the prompt and it will walk you through the setup.New to this?

Before you install

  • Only download from the official GitHub page. Copies with similar names exist for many popular projects.
  • License (MIT): Very permissive: free to use, change and share, including for business.
  • More on staying safe

Where people are talking about it