LlamaIndex

LlamaIndex is an open-source data framework for building LLM applications, created by Jerry Liu in 2022. The company (formerly known as GPT Index) has raised over $30 million and provides tools specifically focused on connecting large language models to private data sources.

LlamaIndex specializes in data ingestion, indexing, and retrieval — the critical infrastructure for RAG (retrieval-augmented generation) applications. The framework supports over 160 data connectors (databases, APIs, file systems, SaaS tools) and provides sophisticated indexing strategies including vector stores, knowledge graphs, and hybrid approaches. LlamaIndex also offers LlamaParse (document parsing for complex PDFs and documents) and LlamaCloud (managed RAG-as-a-service).

LlamaIndex fills a complementary niche to LangChain in the AI development ecosystem: while LangChain provides broad orchestration for LLM applications, LlamaIndex goes deeper on the data connection and retrieval problem. The framework is particularly popular with enterprises building AI applications over proprietary document collections — legal firms, financial institutions, and healthcare organizations that need AI to accurately retrieve and cite information from complex internal knowledge bases.