head to head · open source
llama_index vs langchain4j
llama_index has 52,202 GitHub stars, 8,162 forks, 770 open issues and last shipped yesterday. langchain4j has 13,116 stars, 2,555 forks, 878 open issues and last shipped 2 days ago. llama_index leads on adoption by 298% (52,202 vs 13,116 stars). llama_index is written in Python under MIT; langchain4j is written in Java under Apache-2.0. llama_index has attracted 16% as many forks as stars, langchain4j 19%. llama_index was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (llm), so they are genuine substitutes rather than adjacent tools.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
← all 8884 open source comparisons
Side by side
| llama_index | langchain4j | |
|---|---|---|
| GitHub stars | ★ 52K | ★ 13K |
| License | MIT | Apache-2.0 |
| Written in | Python | Java |
| Last push | 2026-09-17 | 2026-09-16 |
| Forks | ⑂ 8.2K | ⑂ 2.6K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick llama_index if
- You weight community size — 52K stars and counting
- You want the MIT license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick langchain4j if
- You want the langchain4j feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Java
- You evaluated both and langchain4j fits your workflow better
About llama_index
LlamaIndex is an MIT licensed, open source Python framework for building agentic applications — retrieval augmented generation systems, agents and multi agent workflows — on top of private documents and data, and it is aimed at AI engineers and teams who need to connect large language models to their own sources of context.
read the full llama_index overview →
About langchain4j
LangChain4j is an Apache 2.0, open source, idiomatic Java library for building LLM powered applications on the JVM, aimed at Java developers and enterprise teams who want one unified API over many LLM providers and embedding stores without leaving the Java ecosystem.
read the full langchain4j overview →
More in AI & Machine Learning
Related comparisons
More Machine Learning Infrastructure projects
Compare either of these against the rest of the Machine Learning Infrastructure field.
Frequently asked questions
Is llama_index or langchain4j more popular?
llama_index has 52,202 GitHub stars and langchain4j has 13,116. llama_index has the larger community by that measure.
Are llama_index and langchain4j free?
Both are open source. llama_index is licensed under MIT and langchain4j under Apache-2.0. Neither carries a licence fee.
What is the difference between llama_index and langchain4j?
llama_index is written in Python and langchain4j in Java. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, llama_index or langchain4j?
Choose llama_index if you want the larger community (52,202 stars) or its MIT licence terms. Choose langchain4j if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.