What is LlamaIndex?
LlamaIndex (formerly GPT Index) is a data framework specifically designed for connecting custom data sources to large language models, with a primary focus on retrieval-augmented generation and semantic search applications. It provides comprehensive tools for data ingestion, indexing, storage, and querying, making it particularly well-suited for building applications that need to reason over private or domain-specific documents and data.
The framework excels at handling various data sources and formats through its extensive collection of data loaders and connectors. It supports different indexing strategies (vector indexes, tree indexes, keyword indexes, knowledge graphs) and provides sophisticated query engines that can combine multiple retrieval strategies, perform multi-step reasoning, and handle complex queries requiring information synthesis from multiple sources. LlamaIndex emphasizes data-centric concerns that are central to making LLMs useful for real-world applications.
While LangChain offers broader scope including agent frameworks and complex workflows, LlamaIndex focuses deeply on the data ingestion and retrieval aspects of LLM applications. The frameworks are often complementary, and some developers use both in the same application. LlamaIndex's query engines, response synthesizers, and index abstractions provide powerful primitives for building sophisticated retrieval systems, making it a popular choice for knowledge base applications, document Q&A systems, and semantic search engines.