Open-source alternatives to LlamaIndex

LlamaIndex is already open source — its core library is Apache-2.0-licensed and free to use commercially, with a large ecosystem of data connectors and integrations for building retrieval-augmented (RAG) applications. This page isn't about escaping proprietary software; it's about comparing it to adjacent open-source agent frameworks.

Letta (formerly MemGPT) approaches a related but distinct problem: rather than focusing on document ingestion and retrieval pipelines like LlamaIndex, it's built around stateful agents with persistent memory that's meant to improve over time. Use LlamaIndex when your core need is RAG over documents; consider Letta when the priority is long-running agents that retain and build on memory across sessions.

FAQ

Is there a free, open-source alternative to LlamaIndex?

LlamaIndex is already open source and free. Letta is another Apache-2.0-licensed option, focused on persistent agent memory rather than document retrieval pipelines.

What's the best open-source alternative to LlamaIndex?

For RAG and document-retrieval pipelines, LlamaIndex itself remains a leading open-source choice. Letta is the better pick specifically when you need agents that retain state and memory across long-running sessions.

What are the top open-source alternatives to LlamaIndex?

Browse all open-source alternatives to LlamaIndex above, or explore the full Developer Tools category for more options.