head to head · open source
headroom vs outlines
headroom has 78,657 GitHub stars, 6,141 forks, 643 open issues and last shipped yesterday. outlines has 15,998 stars, 911 forks, 166 open issues and last shipped 1 months ago. headroom leads on adoption by 392% (78,657 vs 15,998 stars). headroom is written in Python under Apache-2.0; outlines is written in Python under Apache-2.0. headroom has attracted 8% as many forks as stars, outlines 6%. headroom 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
| headroom | outlines | |
|---|---|---|
| GitHub stars | ★ 79K | ★ 16K |
| License | Apache-2.0 | Apache-2.0 |
| Written in | Python | Python |
| Last push | 2026-11-02 | 2026-09-21 |
| Forks | ⑂ 6.1K | ⑂ 911 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick headroom if
- You weight community size — 79K 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 headroom
Quickstart · Install · Proof · Agents · Docs · Discord · llms.txt AI agents / LLMs: read /llms.txt here, or fetch the live index · full docs blob . Headroom compresses everything your AI agent reads — tool outputs, logs, RAG chunks, files, and conversation history — before it reaches the LLM. Same answers, fraction of the tokens. Compression runs on your machine; no prompt or file content is sent anywhere to be compressed. 10,144 → 1,260 tokens. The same FATAL found. What it does Library — compress(messages) in Python or TypeScript, inline in any app. Proxy — headroom proxy port 8787 , zero code changes, any…
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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 headroom or outlines more popular?
headroom has 78,657 GitHub stars and outlines has 15,998. headroom has the larger community by that measure.
Are headroom and outlines free?
Both are open source. headroom is licensed under Apache-2.0 and outlines under Apache-2.0. Neither carries a licence fee.
What is the difference between headroom and outlines?
headroom 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, headroom or outlines?
Choose headroom if you want the larger community (78,657 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.