LlamaIndex

Framework for connecting LLMs to your own documents and data

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What is LlamaIndex?

LlamaIndex is an open-source framework for building retrieval and agent applications on top of language models. It handles the unglamorous parts: loading documents from many sources, splitting them into chunks, creating embeddings, storing them in an index, and retrieving the right context for a query. On top of that sit query engines, chat engines, tool-calling agents and workflow orchestration. The differentiator is the breadth of connectors and index types, which lets a team assemble a working retrieval pipeline in days rather than wiring every piece by hand.

Last updated: 2026-09-20. This site only provides an index; for exact features, pricing, and licensing, see the official website.

Key features

  • Data connectors for files, Notion, Slack, databases and web pages
  • Index structures including vector, keyword, tree and knowledge graph
  • Query and chat engines that return responses with citations
  • Agent and workflow abstractions for multi-step tool use
  • Integrations with most vector stores and model providers
  • Evaluation modules for measuring retrieval and answer quality

Pros & cons

Strengths

  • Very wide set of loaders and integrations out of the box
  • Open source with a steady release cadence and active community
  • Handles chunking and retrieval plumbing so you do not

Watch out for

  • Abstractions are numerous and the API has moved between versions
  • Debugging a poor answer means inspecting several layers
  • Production deployments still require your own infrastructure

Best for & use cases

rag applications, document question answering, data agents, retrieval evaluation

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FAQ

What problem does LlamaIndex solve?

It handles the data plumbing behind retrieval applications: loading documents, chunking them, creating embeddings, storing vectors and fetching the right context. That is the work most teams would otherwise write themselves.

Do I need a vector database?

Not necessarily to start. LlamaIndex ships with simple in-memory stores for prototyping. For anything at scale you will want a real vector store, and the framework supports most of the popular ones.

Is it only for retrieval?

No. Retrieval is the core, but the project also covers chat engines, tool-calling agents, multi-step workflows and evaluation, so it can support an agent application as well as a search one.