llms.txt Validator - Free SEO tool

The llms.txt Validator analyzes the llms.txt file of any domain and reports whether it is correctly formatted for AI crawlers. Paste your URL or domain into the tool above to get an instant diagnostic.

What is llms.txt and why does it matter?

llms.txt is a plain-text convention, analogous to robots.txt, that tells large language models and AI search engines how to navigate a website. Placed at the root of a domain (e.g., example.com/llms.txt), it lists the key pages, sections, and files an AI crawler should prioritize. Without it, AI systems must guess which content is authoritative -- and they often guess wrong.

As AI Overviews, ChatGPT, and Perplexity increasingly drive discovery, having a well-formed llms.txt is one of the fastest technical wins available for Generative Engine Optimization (GEO).

What the tool above checks

File presence: is llms.txt accessible at the expected path?
Syntax validity: correct Markdown heading structure, no malformed links.
Required sections: a valid file typically includes a site title, a short description, and at least one section of URLs.
Link reachability: the validator samples listed URLs and flags any returning 4xx or 5xx errors.
Encoding: the file must be served as UTF-8 plain text; wrong MIME types break AI parsers.
File size: an oversized llms.txt may be truncated by crawlers; the tool warns if the file exceeds recommended limits.

How to interpret the results and act

A green status means the file is reachable and well-formed. Check that listed URLs are genuinely your most important pages.
A 404 error on the file itself means no llms.txt exists yet. Create one using the official spec at llmstxt.org and deploy it at the root.
Broken links inside the file reduce trust: fix redirects or remove stale URLs immediately.
Wrong MIME type (e.g., text/html instead of text/plain): update your server or CDN headers.
After any fix, re-run the tool above to confirm the issue is resolved before requesting re-indexing.

Benchmark: AI visibility starts with crawl access

Studies show that AI Overviews appear on roughly 31% of Google queries (2025). A site that blocks or confuses AI crawlers is invisible in this growing slice of search. A correct llms.txt removes one of the most common technical barriers to GEO visibility.

For ongoing monitoring of your AI search presence across ChatGPT, Perplexity, and Gemini, Sorank tracks citations and visibility automatically.

Frequently asked questions

Where should I place my llms.txt file?

At the root of your domain, accessible at https://yourdomain.com/llms.txt. It must be served as UTF-8 plain text (Content-Type: text/plain).

Does having a valid llms.txt guarantee I appear in AI answers?

No. A valid file removes a technical barrier but AI models also weigh content quality, authority signals, and citation patterns. It is a necessary first step, not a sufficient one.

How often should I update my llms.txt?

Whenever you add important new pages or restructure your site. At minimum, review it quarterly and re-run this validator after each update to catch broken links.