head to head · open source
langchain vs outlines
langchain has 146,538 GitHub stars, 24,504 forks, 492 open issues and last shipped yesterday. outlines has 15,825 stars, 880 forks, 166 open issues and last shipped 9 days ago. langchain leads on adoption by 826% (146,538 vs 15,825 stars). langchain is written in Python under MIT; outlines is written in Python under Apache-2.0. langchain has attracted 17% as many forks as stars, outlines 6%. langchain was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (generative-ai), 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
| langchain | outlines | |
|---|---|---|
| GitHub stars | ★ 147K | ★ 16K |
| License | MIT | Apache-2.0 |
| Written in | Python | Python |
| Last push | 2026-09-17 | 2026-09-09 |
| Forks | ⑂ 25K | ⑂ 880 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick langchain if
- You weight community size — 147K stars and counting
- You want the MIT license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick outlines if
- You want the outlines feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Python
- You evaluated both and outlines fits your workflow better
About langchain
LangChain is an open source framework for building agents and LLM powered applications, written in Python and released under the MIT license. It lives in the AI and machine learning ecosystem, specifically among AI development platforms, and it works by chaining together interoperable components and third party integrations so that AI application development becomes simpler. The project describes itself as the agent engineering platform, and its abstractions are designed to keep applications working as the underlying technology evolves.
read the full langchain overview →
About outlines
Outlines is a Python library for structured generation with large language models, released under the Apache 2.0 license and maintained by the team at .txt. It lives in the AI and machine learning ecosystem, specifically among AI development platforms and structured generation tooling, and it is distributed through PyPI. The project describes itself as a way to guarantee structured outputs during generation rather than repairing them afterward, and its topic list places it alongside work on context free grammars, regular expressions, JSON, prompt engineering, and symbolic AI.
read the full outlines overview →
More in AI & Machine Learning
Related comparisons
More AI Development Platforms projects
Compare either of these against the rest of the AI Development Platforms field.
Frequently asked questions
Is langchain or outlines more popular?
langchain has 146,538 GitHub stars and outlines has 15,825. langchain has the larger community by that measure.
Are langchain and outlines free?
Both are open source. langchain is licensed under MIT and outlines under Apache-2.0. Neither carries a licence fee.
What is the difference between langchain and outlines?
langchain is written in Python and outlines in Python. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, langchain or outlines?
Choose langchain if you want the larger community (146,538 stars) or its MIT licence terms. Choose outlines if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.