LLMS.txt Validator
Validate llms.txt structure and catch the errors that make it unusable.
Last reviewed by the Radiatus Cloud team
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Structural rules to check
Exactly one H1 carrying the site name. Section headings at H2. Link lists in standard markdown with a description following a colon. Any blockquote summary immediately after the H1. Multiple H1s or headings jumping straight to H3 break the expected shape, and a parser reading the file positionally will misattribute entries.
Broken links are the common fault
Entries pointing at 404s, at redirects, or at URLs that changed during a site migration. A file that recommends missing pages is worse than none, because it spends a model's limited budget on failed fetches. Every URL should return 200 directly rather than through a redirect chain.
Check against robots.txt and canonicals
A page listed here but disallowed in robots.txt will not be fetched. A page whose canonical points elsewhere should not be listed — the canonical target should be. These contradictions are invisible when the file is written by hand from a list of favourites.
Descriptions do the selection work
Entries with no description force a model to fetch a page to discover whether it is relevant. A specific one-line description is what allows the file to serve its purpose without any fetching, and it is the difference between a useful file and a decorated sitemap.
Absolute URLs, served as plain text
Relative paths resolve inconsistently for a fetcher that did not arrive through the site. The file belongs at the domain root, served as text/markdown or text/plain — serving it as HTML with a template wrapper defeats parsing entirely.
Related tools
- Meta Tag Analyzer — Check a page's meta tags for the problems that actually affect indexing and click-through.
- Redirect Chain Checker — Trace the full path of redirects (301/302) to find loops or lost link juice.
- Robots.txt Validator — Validate robots.txt syntax and check whether a specific URL is allowed or blocked for a given crawler.
- Sitemap Generator (Lite) — Generate a valid XML sitemap with lastmod dates and correct structure, and learn which URLs belong in it and which do not.
Frequently Asked Questions
What structure should llms.txt have?
One H1 with the site name, an optional blockquote summary, then H2 sections containing markdown link lists with a description after each colon.
What is the most common error?
Broken or redirecting links. A file recommending missing pages spends a model's limited budget on failed fetches, which is worse than having no file.
Should I list pages blocked in robots.txt?
No. robots.txt still applies, so those pages will not be fetched. The same goes for pages whose canonical points elsewhere — list the canonical target instead.
Do descriptions matter?
They are the point. Without them a model must fetch each page to judge relevance, which defeats the purpose of the file.
Privacy & Security
Validated locally in your browser. No data is sent to any server.
How to Use
Paste your llms.txt content and click Validate.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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