# llms.txt Validator

> Agent-friendly Markdown of https://www.buildseo.org/free-tools/llms-txt-validator — full index for AI agents: https://www.buildseo.org/llms.txt

Validate a site's llms.txt against the llmstxt.org structure.

## How it works

Enter any URL on the site and the validator fetches /llms.txt from that origin and checks the llmstxt.org structure: a single H1 title, a blockquote summary, and '## Section' headings whose list items are markdown links with descriptions.

It then samples the linked URLs live — an llms.txt that sends AI agents to 404s is worse than none — and compares the same-origin links against your XML sitemap to warn when the file has drifted stale.

Findings and section stats download as CSV or JSON, free and instant.

## Frequently asked questions

### What is llms.txt?
A proposed standard (llmstxt.org) for a markdown index at your site root that tells AI agents what your site contains and where the machine-readable versions live — the AI-era counterpart to sitemap.xml.

### What structure does the validator require?
An H1 title on the first line, an optional but recommended '>' blockquote summary, and sections introduced by '## Heading' containing '- `[Name](url)`: description' list items. Malformed list lines are flagged because agents parse that form strictly.

### How does the staleness check work?
Same-origin links in llms.txt are compared against the URLs in your sitemap. When only a small fraction overlap, the file likely predates your current page set — regenerate it alongside the sitemap.

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