head to head · open source
CL4R1T4S vs outlines
CL4R1T4S has 51,737 GitHub stars, 10,551 forks, 127 open issues and last shipped 1 months ago. outlines has 16,002 stars, 910 forks, 166 open issues and last shipped 2 months ago. CL4R1T4S leads on adoption by 223% (51,737 vs 16,002 stars). CL4R1T4S is written in various languages under AGPL-3.0; outlines is written in Python under Apache-2.0. CL4R1T4S has attracted 20% as many forks as stars, outlines 6%. CL4R1T4S 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 | ★ 52K | ★ 16K |
| License | AGPL-3.0 | Apache-2.0 |
| Written in | — | Python |
| Last push | 2026-09-22 | 2026-09-21 |
| Forks | ⑂ 11K | ⑂ 910 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick CL4R1T4S if
- You weight community size — 52K 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 AI SYSTEMS TRANSPARENCY AND OBSERVABILITY FOR ALL! Full extracted system prompts, guidelines, and tools from OpenAI, Google, Anthropic, xAI, Perplexity, Cursor, Windsurf, Devin, Manus, Replit, and more – virtually all major AI models + agents! 📌 Why This Exists "In order to trust the output, one must understand the input." AI labs shape how models behave using massive, unseen prompt scaffolds. Because AI is a trusted external intelligence layer for a growing number of humans, these hidden instructions can affect the perceptions and behavior of the public. These prompts define: What AIs can’t say What…
read the full CL4R1T4S overview →
About outlines
🗒️ Structured outputs for LLMs 🗒️ Made with ❤👷️ by the team at .txt Trusted by NVIDIA, Cohere, HuggingFace, vLLM, etc. [![PyPI Version][pypi version badge]][pypi] [![Downloads][downloads badge]][pypistats] [![Stars][stars badge]][stars] [![Discord][discord badge]][discord] [![Blog][dottxt blog badge]][dottxt blog] [![Twitter][twitter badge]][twitter] The .txt API is currently in early access. Request access here → 🚀 Building the future of structured generation We're working with select partners to develop new interfaces to structured generation. Need XML, FHIR, custom schemas or grammars? Let's talk. Audit…
read the full outlines overview →
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Frequently asked questions
Is CL4R1T4S or outlines more popular?
CL4R1T4S has 51,737 GitHub stars and outlines has 16,002. 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 (51,737 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.