llms.txt generator

llms.txt Validator

Check any llms.txt file against the proposal — structure, format and every link.

Or paste a llms.txt file instead

What gets validated

The validator applies the five requirements the llmstxt.org proposal actually cares about, in order of severity:

CheckWhat it requiresWhy it fails files
H1 titleFirst line is # Site name — the site’s name, not “llms.txt”The H1 is how a reader knows whose file this is; a generic one breaks identification.
Summary blockquoteA > blockquote with a one-or-two sentence site summaryThe most-skipped requirement in the wild — even large sites omit it.
H2 sectionsLinks grouped under descriptive ## headingsAn unsectioned wall of links gives an agent no way to prioritize.
Link formatEvery entry is [name](absolute-url)Relative or bare URLs break the “fetchable from anywhere” contract.
Links reachableEvery linked page responds successfullyDead or redirected entries waste the agent’s requests and erode trust.

Validate a live site or a draft

Enter a domain and the validator requests /llms.txt from it directly — nothing is stored, and the check runs server-side, so the results do not depend on your browser. Working on a draft? Paste the content instead: the same checks run on the text you provide, which is handy before you publish. For a known-good baseline, validatethis site’s own file — it is the first file this tool was run against, and it stays in sync with the proposal.

Common validation failures, and the fix

SymptomCauseFix
“Missing H1”File starts with a heading level other than #, or with textOpen with # Your Site Name
“Missing summary blockquote”Description written as a plain paragraphPreface it with > on the line after the H1
“not an absolute URL”Entries like (/docs)Write (https://your-site.com/docs)
“N links unreachable”Typos, moved pages, redirectsFix or drop the dead entries — an index that lies is worse than none
No sectionsAll links in one listGroup under ## Docs, ## Pricing-style headings

From validation to a valid file

If your file fails more than it passes, the fastest path is to regenerate rather than patch: the llms.txt generator crawls your site, applies the proposal’s structure from the start, and shows the decision table behind every entry. Validation then becomes a confirmation step instead of a repair job. Checking a file someone else shipped? The checker page covers the same ground from a different angle (llms.txt checker).

FAQ

What does a llms.txt validator check?
It compares your file against the llmstxt.org proposal: the required H1, the required summary blockquote, the presence of H2 sections, the markdown link format with absolute URLs, and whether the linked pages actually resolve.
Is validation different from generation?
Yes. Generation writes a file from your live site; validation reads a file — yours or anyone’s — and reports where it deviates from the proposal. Use the validator after hand-editing a generated file, or to audit another site’s file.
Why does link reachability matter?
A llms.txt file is only as good as its links. Entries pointing at redirects, 404s or pages behind logins waste the agent’s request and make the index untrustworthy. The validator requests every link and reports the failures.
My file passes — am I done?
Validation means the file follows the proposal. Whether it lists the right pages is an editorial question: read the descriptions and make sure each entry would help someone decide whether to visit.
Can I validate a file that is not published yet?
Yes — paste the content instead of entering a URL. The same five checks run against the text you provide.