**An `llms.txt` file is like `robots.txt` for large language models — a Markdown map that tells AI systems what your site is and which pages are authoritative.** This check confirms yours is published at your site root, returns a `200`, is served as real Markdown (not an HTML error page), and contains a summary plus links to your key URLs. A clean `llms.txt` helps AI engines represent and cite you accurately.
It fetches yourdomain.com/llms.txt and confirms it's a usable file for AI systems. Specifically:
- Reachable — it returns a 200 at the site root and isn't blocked by robots.txt or your CDN.
- Markdown, not HTML — it's served as plain Markdown, not an HTML page or a custom 404.
- Has a summary — a short title (H1) and a one-paragraph description of what the site is.
- Curated links — Markdown links to your most important, authoritative pages.
A valid, well-formed file passes; one that exists but is thin or malformed is a warning; no llms.txt at all is a fail.
GEObubbly fetches /llms.txt, confirms a 200 response, checks that the content is Markdown rather than an HTML error page, and looks for a summary and links. It's a core GEO / LLM Readiness check worth 3 points — a cheap, high-leverage signal because so few sites have one yet.
When an AI engine answers a question about your product or company, it stitches together whatever it can find — and without guidance, that can be stale, scattered or wrong. An llms.txt gives those systems a curated, high-signal map: here's what we do, and here are the canonical pages to trust. That reduces misrepresentation and steers engines toward your best content rather than letting them guess from fragments. Adoption is still early, which is precisely the opportunity: publishing a clean llms.txt now is a cheap, low-risk edge while most competitors don't have one. It won't rescue a site that's blocked or unindexable, but paired with answer-first content, fast server-rendered pages and accurate structured data, it measurably improves how correctly ChatGPT, Perplexity and other engines describe and cite you. Think of it as the guided tour you hand the AI — one of the most actionable wins in GEO / LLM Readiness.
An llms.txt is a Markdown file placed at your site root (/llms.txt) that gives AI systems a curated summary of what your site is and links to your most authoritative pages. It works like a guided tour for large language models — the opposite of making them crawl and guess. When an AI engine describes or cites your brand, it can anchor to this authoritative source instead of stitching together stale or scattered fragments, which reduces misquoting and helps it represent you accurately.
Fetch https://yourdomain.com/llms.txt and confirm three things: it returns a 200 status, it's served as plain Markdown rather than an HTML error or redirect page, and it contains a clear summary plus working links to your key URLs. It also must not be blocked by robots.txt or challenged by your CDN. GEObubbly's checker above performs all of these validations automatically — paste your URL to see exactly which requirements pass or fail and where the file falls short.
It belongs at the root of your domain, served from https://yourdomain.com/llms.txt, exactly as robots.txt lives at the root. It must return a 200 and not be blocked by robots.txt rules or your CDN, because AI systems look for it specifically at that root path. Sub-folder locations such as /docs/llms.txt are not part of the emerging standard and won't be discovered, so placing the file anywhere other than the root means it effectively doesn't exist as far as LLMs are concerned.
A well-formed llms.txt opens with a short H1 title naming your site, then a one-paragraph summary of what you do, followed by curated Markdown links to your most important, authoritative pages — documentation, flagship products, your about page, key guides. Keep it high-signal and current: it's a guided tour for AI models, not a full sitemap, so include only the pages you genuinely want engines to read, prioritise and cite when answering questions about you.
Adoption is still early, which is what makes it a low-cost, low-risk edge right now — very few of your competitors have one. A clean llms.txt won't rescue a broken or unindexable site on its own, but paired with answer-first content, fast server-rendered pages and accurate structured data, it measurably improves how correctly ChatGPT, Perplexity and other engines describe, prioritise and cite you. It steers AI systems toward your best, canonical pages rather than letting them guess from scattered fragments, reducing misquoting and outdated claims.