head to head · open source
Mem0 vs outlines
Mem0 has 65,505 GitHub stars, 7,683 forks, 742 open issues and last shipped yesterday. outlines has 15,825 stars, 880 forks, 166 open issues and last shipped 9 days ago. Mem0 leads on adoption by 314% (65,505 vs 15,825 stars). Mem0 is written in Python under Apache-2.0; outlines is written in Python under Apache-2.0. Mem0 has attracted 12% as many forks as stars, outlines 6%. Mem0 was the more recently maintained of the two, and both are self-hostable with no licence fee.
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
| Mem0 | outlines | |
|---|---|---|
| GitHub stars | ★ 66K | ★ 16K |
| License | Apache-2.0 | Apache-2.0 |
| Written in | Python | Python |
| Last push | 2026-09-17 | 2026-09-09 |
| Forks | ⑂ 7.7K | ⑂ 880 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Mem0 if
- You weight community size — 66K stars and counting
- You want the Apache-2.0 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 Mem0
Mem0 is an open source memory layer for AI agents and applications, designed to store, retrieve, and manage persistent context across interactions. It lives in the Python based AI development ecosystem and provides infrastructure that enables agents and apps to remember user preferences, conversation history, and state over time—moving beyond ephemeral chat sessions toward truly adaptive systems.
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 →
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Frequently asked questions
Is Mem0 or outlines more popular?
Mem0 has 65,505 GitHub stars and outlines has 15,825. Mem0 has the larger community by that measure.
Are Mem0 and outlines free?
Both are open source. Mem0 is licensed under Apache-2.0 and outlines under Apache-2.0. Neither carries a licence fee.
What is the difference between Mem0 and outlines?
Mem0 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, Mem0 or outlines?
Choose Mem0 if you want the larger community (65,505 stars) or its Apache-2.0 licence terms. Choose outlines if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.