llms.txt is a plain-text markdown file you publish at the root of your domain — https://yourdomain.com/llms.txt — that tells AI systems what your site is about, what your most important pages are, and where to find your documentation. It is the AI-era equivalent of robots.txt, but for context rather than crawl rules.
Why it matters: When an AI agent visits your site, it does not have time to crawl every page. Without llms.txt, it guesses. With llms.txt, you tell it exactly which pages matter and how to think about your brand. Brands that ship one report 15-40% lifts in Perplexity and Claude citations.
The format (with example)
llms.txt uses a specific markdown structure:
# VibecodeAEO
> AI Brand Intelligence platform. We measure how often ChatGPT, Perplexity,
> and Gemini cite your brand and tell you exactly what to change to win
> more citations.
## Product
- [How AI Visibility Scoring works](https://vibecodeaeo.com/seo/learn/scoring): The 0-100 metric
- [Pricing](https://vibecodeaeo.com/seo#pricing): Plans for solo, brand, and agency
- [Glossary](https://vibecodeaeo.com/seo/glossary): Plain-English AEO definitions
## Reference
- [What is AEO](https://vibecodeaeo.com/seo/what-is-aeo): Definitive guide
- [AEO vs SEO](https://vibecodeaeo.com/seo/aeo-vs-seo): Comparison
## Optional
- [About](https://vibecodeaeo.com/seo/about): Company background
The rules
Single H1 with your site or brand name.
Blockquote summary — one paragraph, plain language, what your brand is and does.
H2 sections grouping links by purpose (Product, Docs, Reference, etc.).
Markdown links in lists. Each link has a colon-then-description so the AI knows what it points to.
Optional ## Optional section at the end for “nice to have” pages the AI can deprioritize.
How to ship it in 10 minutes
List your top 5-15 most important URLs — product, pricing, docs, glossary, key reference content.
Write one paragraph describing your brand in plain language.
Drop the markdown into a text file named llms.txt.
Upload it to your web root so it serves at https://yourdomain.com/llms.txt.
(Optional) Add a <link rel="llms" href="/llms.txt"> in your homepage <head> for discoverability.
Test by curling the URL or using VibecodeAEO's validator.
Common mistakes
Linking to too much. If everything is important, nothing is. Keep it under 20 links.
Forgetting descriptions. A bare link tells the AI nothing. Always include the colon-description.
Stale content. If you change a page's URL, update llms.txt. Treat it like a sitemap.
Marketing copy. Skip the buzzwords. AI engines trained on millions of marketing pages can detect fluff and discount it.
Wrong location. Must be at root, not in /docs/llms.txt or anywhere else.
FAQ
What is llms.txt?
llms.txt is a markdown file served at the root of a domain (https://yourdomain.com/llms.txt) that gives AI systems a curated, machine-readable summary of your brand, products, and key documentation links. It was proposed by Jeremy Howard in 2024.
Is llms.txt an official standard?
Not yet ratified by the IETF, but adopted by Anthropic, Mistral, and several major SaaS brands. The proposal is hosted at llmstxt.org and the format is stable.
Where do I put llms.txt?
At the root of your domain, the same place as robots.txt. URL: https://yourdomain.com/llms.txt. Some adopters also publish llms-full.txt for a deeper version.
Does shipping llms.txt actually move citations?
Yes, especially for Perplexity and Claude which are documented to retrieve it. Effect on ChatGPT is harder to attribute but trending positive. Ship it — the cost is one hour of work.
What format does llms.txt use?
Plain markdown with a specific structure: H1 site name, blockquote summary, optional notes, then H2 sections each containing a markdown list of links with descriptions. See the example on this page or visit llmstxt.org for the spec.