LangChain
open-sourceLangChain is an open-source framework for building LLM applications with chains, tools, and agents.
LangChain provides libraries and patterns to connect large language models to data sources, tools, and memory so developers can ship chatbots, copilots, and autonomous agents. Components include prompt templates, retrieval augmented generation (RAG) helpers, and integrations with vector databases and enterprise systems.
The core packages are open source under permissive licenses, with optional commercial services (such as LangSmith) for observability and evaluation. LangChain is widely adopted in Python and TypeScript ecosystems.
Engineering teams use LangChain when they want composable abstractions and a large integration surface rather than wiring every provider API by hand from scratch.