llms.txt Validator

What the llms.txt Validator checks

The llms.txt standard gives large language models a clean, curated map of your most important content. A malformed file can cause AI systems to misread your structure or miss key pages — so this validator checks every requirement from the official llmstxt.org spec and reports each problem on the exact line, with a concrete fix.

• Single H1 title — exactly one # Project Name, as the first line (required).
• Blockquote summary — a short > summary after the H1 (recommended).
• Section link lists — ## Section headings with items in the - [name](url): notes format.
• Valid links — absolute http(s) URLs, no duplicates, optional reachability check.
• Size & count guidelines — under ~50KB and ~100 links for llms.txt; up to 500KB for llms-full.txt.

How to validate your llms.txt file

1. Load the file. Choose Fetch URL and enter your domain (the validator looks for /llms.txt), or choose Paste content to check a draft before you publish it.
2. Fix errors first, then warnings. Errors break the spec, such as a missing H1 or a malformed link line. Warnings are recommendations, such as a missing summary. Each one lists the line number and a suggested fix.
3. Check the links. Turn on the link check to confirm every URL in the file actually loads, so AI systems are not pointed at dead pages.
4. Publish at the root. Upload the corrected file to https://yourdomain.com/llms.txt and run the validator against the live URL once more.

No file yet? Build one with the llms.txt generator. To see whether AI assistants already mention your brand, run the AI visibility checker, and if you would rather keep some AI crawlers out entirely, the AI bot blocker writes the robots.txt rules for you.