Overview
LlamaIndex (formerly GPT Index) is a data framework specifically designed for connecting LLMs with external data sources. Having raised $10 million, LlamaIndex has established itself as the go-to framework for building RAG (Retrieval-Augmented Generation) applications. While LangChain is more general-purpose, LlamaIndex focuses deeply on data ingestion, indexing, and retrieval.
The framework excels at creating custom knowledge bases from diverse data sources, with sophisticated indexing strategies and retrieval methods. LlamaIndex provides simple interfaces for common use cases while offering advanced customization for complex scenarios, making it accessible to both beginners and experts.
Key Features
**Data Connectors**: 160+ connectors for diverse data sources**Advanced Indexing**: Multiple index types for different use cases**Query Engines**: Sophisticated retrieval and query strategies**Chat Engines**: Conversation interfaces with context retention**Agent Tools**: Convert indexes into agent tools**Evaluation**: Built-in evaluation framework for RAG quality**LlamaCloud**: Managed parsing and ingestion service**LlamaParse**: Advanced document parsing for PDFs and complex formatsWhen to Use LlamaIndex
LlamaIndex is ideal for:
RAG applications with complex data sourcesBuilding searchable knowledge bases from documentsApplications requiring sophisticated retrieval strategiesProjects needing strong document parsing capabilitiesTeams focused specifically on data-augmented LLM appsUse cases requiring evaluation of RAG qualityPros
Best-in-class for RAG applicationsExtensive data connector libraryAdvanced indexing and retrieval strategiesStrong focus on document parsingExcellent documentation and examplesActive community and developmentBoth simple and advanced APIsLlamaParse for complex document handlingCons
More focused scope than general frameworksSmaller ecosystem than LangChainLess suitable for non-RAG use casesTypeScript version less mature than PythonSome advanced features only in paid tiersCan be complex for simple use casesLess emphasis on agents compared to LangChainPricing
**Open Source**: Free framework**LlamaCloud**: Free tier, then $69/month**LlamaParse**: $0/month for 1k pages, then paid tiers**Enterprise**: Custom pricing for support and features