head to head · open source
CL4R1T4S vs outlines
CL4R1T4S has 50,059 GitHub stars, 10,280 forks, 127 open issues and last shipped 10 days ago. outlines has 15,841 stars, 882 forks, 166 open issues and last shipped yesterday. CL4R1T4S leads on adoption by 216% (50,059 vs 15,841 stars). CL4R1T4S is written in various languages under AGPL-3.0; outlines is written in Python under Apache-2.0. CL4R1T4S has attracted 21% as many forks as stars, outlines 6%. outlines was the more recently maintained of the two, and both are self-hostable with no licence fee. The two share 1 topic tag (prompt-engineering), 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
| CL4R1T4S | outlines | |
|---|---|---|
| GitHub stars | ★ 50K | ★ 16K |
| License | AGPL-3.0 | Apache-2.0 |
| Written in | — | Python |
| Last push | 2026-09-10 | 2026-09-19 |
| Forks | ⑂ 10K | ⑂ 882 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick CL4R1T4S if
- You weight community size — 50K stars and counting
- You want the AGPL-3.0 license terms
- 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 CL4R1T4S
CL4R1T4S is an AGPL 3.0 repository of full extracted system prompts, guidelines and tools from the major AI models and agents — ChatGPT, Claude, Gemini, Grok, Perplexity, Cursor, Lovable, Replit and more — for anyone who wants to know what instructions sit behind the AI systems they use.
read the full CL4R1T4S 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 →
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Frequently asked questions
Is CL4R1T4S or outlines more popular?
CL4R1T4S has 50,059 GitHub stars and outlines has 15,841. CL4R1T4S has the larger community by that measure.
Are CL4R1T4S and outlines free?
Both are open source. CL4R1T4S is licensed under AGPL-3.0 and outlines under Apache-2.0. Neither carries a licence fee.
What is the difference between CL4R1T4S and outlines?
CL4R1T4S is written in various languages 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, CL4R1T4S or outlines?
Choose CL4R1T4S if you want the larger community (50,059 stars) or its AGPL-3.0 licence terms. Choose outlines if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.