Overview
LangChain is the most popular open-source framework for building applications with large language models. Founded by Harrison Chase and having raised $25 million, LangChain has become the de facto standard for LLM application development. It provides a comprehensive set of tools for building everything from simple chatbots to complex multi-agent systems.
The framework offers abstractions for prompts, chains, agents, memory, and retrieval, making it easier to build sophisticated LLM applications. LangChain's modular design allows developers to swap components easily, and its extensive integrations ecosystem connects to virtually every LLM provider, vector database, and tool.
Key Features
**Chains**: Compose LLM calls and processing steps**Agents**: Build autonomous agents with tool usage**Memory**: Built-in conversation and context memory**RAG Support**: Complete toolkit for retrieval-augmented generation**LangSmith**: Observability and debugging platform**LangServe**: Deploy LangChain applications as APIs**Extensive Integrations**: 700+ integrations with tools and services**Multi-Language**: Python and JavaScript/TypeScript SDKsWhen to Use LangChain
LangChain is ideal for:
Building RAG applications with LLMsCreating AI agents with tool usageComplex workflows combining multiple LLM callsApplications requiring extensive integrationsTeams wanting a proven, well-documented frameworkProjects needing both Python and JavaScript supportPros
Largest ecosystem and community in LLM developmentComprehensive documentation and tutorialsExtensive integration libraryActive development with frequent updatesBoth open-source and commercial offeringsLangSmith for production monitoringStrong backing and fundingMulti-language supportCons
Can be overly complex for simple use casesAbstraction layers can hide important detailsFrequent API changes and deprecationsPerformance overhead from abstractionsLearning curve for advanced featuresCan encourage over-engineeringSome integrations are poorly maintainedPricing
**Open Source**: Free framework**LangSmith**: Free tier, then $39/month per user**LangChain Enterprise**: Custom pricing