head to head · open source
PageIndex vs langchain4j
PageIndex has 35,678 GitHub stars, 3,148 forks, 103 open issues and last shipped yesterday. langchain4j has 13,116 stars, 2,555 forks, 878 open issues and last shipped 2 days ago. PageIndex leads on adoption by 172% (35,678 vs 13,116 stars). PageIndex is written in Python under MIT; langchain4j is written in Java under Apache-2.0. PageIndex has attracted 9% as many forks as stars, langchain4j 19%. PageIndex 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.
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Side by side
| PageIndex | langchain4j | |
|---|---|---|
| GitHub stars | ★ 36K | ★ 13K |
| License | MIT | Apache-2.0 |
| Written in | Python | Java |
| Last push | 2026-09-17 | 2026-09-16 |
| Forks | ⑂ 3.1K | ⑂ 2.6K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick PageIndex if
- You weight community size — 36K 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 PageIndex
PageIndex is a vectorless, reasoning based retrieval augmented generation engine written in Python and released under the MIT license. It lives in the AI and machine learning infrastructure ecosystem, with topics spanning RAG, information retrieval, LLM reasoning, context engineering, and agentic AI. Instead of building a vector index, PageIndex generates a hierarchical tree index for each document and then lets a large language model reason its way through that tree, in the same way a human expert turns to the right section of a long report. The project ships as a Python SDK, a hosted cloud service, and a docume…
read the full PageIndex 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 →
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Frequently asked questions
Is PageIndex or langchain4j more popular?
PageIndex has 35,678 GitHub stars and langchain4j has 13,116. PageIndex has the larger community by that measure.
Are PageIndex and langchain4j free?
Both are open source. PageIndex is licensed under MIT and langchain4j under Apache-2.0. Neither carries a licence fee.
What is the difference between PageIndex and langchain4j?
PageIndex 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, PageIndex or langchain4j?
Choose PageIndex if you want the larger community (35,678 stars) or its MIT licence terms. Choose langchain4j if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.