The most popular framework for LLM app development
Introduction
LangChain is the most popular LLM application framework, abstracting model calls, prompt templates, RAG, agents and tool calling into composable chains. With Python/JS ecosystems, massive integrations and tutorials, it is the de facto entry to LLM engineering — LangSmith/LangGraph round out observability and complex orchestration.
Key Features
- Unified model/prompt/chain abstractions
- Full RAG component suite
- Agent and tool-calling framework
- LangSmith observability platform
- Python and JS ecosystems
Pros
- The richest components and tutorials
- A shortcut into LLM engineering
Cons
- Heavy abstractions for simple cases
Pricing
Framework is open-source and free; LangSmith bills by usage.（See official site for current pricing）
FAQ
Still worth learning?
Yes for concepts and ecosystem; simple cases can use official SDKs directly.
What is LangGraph?
A graph-based multi-agent orchestration framework.
LangChain vs LlamaIndex?
LangChain for general apps; LlamaIndex for RAG-heavy data work.
Related Sites
Collected on lucifer.city · Reviewed by the founder