Validate a live llms.txt.
Paste a URL and we fetch the site's /llms.txt, parse it against the llmstxt.org spec, and tell you exactly what is present, what is missing, and how to fix it. Free, no signup.
Tip: drop the leading https://, we add it for you. Private-network URLs (loopback, RFC1918) are rejected.
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What the score actually means
A perfect 20/20 requires all six surfaces the spec calls out: the file exists and is reachable at the root, it starts with a single H1 header, it has at least 3 markdown links, it groups links under H2 sections, it opens with a summary blockquote right after the H1, and the body is at least 300 characters of real content. The 21st point is a bonus for also publishing /llms-full.txt, the longer-form companion that ships the actual prose instead of just links.
Why this matters
Perplexity, Claude's browser search, and ChatGPT's web-browsing tool all look for llms.txt in the first pass when they land on a new domain. A site that publishes a clean llms.txt answers the question "what is this site for" in one round-trip, without scraping ten pages or relying on a search index. That compresses discovery from minutes to milliseconds, and the model cites the file directly in more than one retrieval pass in our tests.
How to fix a low score
If the validator reports no llms.txt at all, the fastest path is our llms.txt generator — paste a URL, get a starter file you can edit and upload. If you have an llms.txt but it is missing specific surfaces, the "How to fix this" section above lists each issue in priority order with a one-line fix. Nothing on that list takes more than a couple of minutes.
Related tools
AI Readiness Checker runs this validator alongside four other categories · llms.txt generator creates a starter file · Live leaderboard shows every URL we've validated · Host analysis directory for per-host deep dives.
We fetch /llms.txt once per validation, with a standard browser User-Agent, and never store the content. The scoring rubric is open source and matches the AI Readiness Checker byte for byte.