Free llms.txt validator

Check the llms.txt you already have: format, file type, size and dead links.

FreeNo sign-upFormat: llmstxt.org

llms.txt validatorFormat: llmstxt.org

Enter your domain to check its /llms.txt file.

How it checks

The file, line by line.

Read against the llmstxt.org format, then every link it lists is opened.

Find the file

/llms.txt on your domain, and llms-full.txt if you have it.

Check the type

A text file, not a web page answering every address.

Check the format

H1 name, summary, H2 sections, Markdown links.

Open the links

The first 12 links, so agents don't hit dead pages.

FAQ

Questions, answered.

What does the llms.txt validator check?

That /llms.txt exists and is a text file (not your 404 page), starts with an H1 name, has a summary and H2 sections of Markdown links with full URLs, is a sensible size, and that the first links it lists open.

Do AI engines use llms.txt?

Some AI tools and agents read it; the major engines have not said they rely on it. It is cheap to add and useful for agents, but it does not replace pages that answer buyer questions.

My site returns a page at /llms.txt. Why does it fail?

Many sites answer every unknown address with their normal page and a 200 status. Agents then read HTML, not your file. Serve a real text file instead.

What is llms-full.txt?

An optional companion with the full text of your docs in one file. The validator notes whether you have one.

How do I fix the problems?

Open the free llms.txt generator: it reads your site, drafts the file, and shows the same format checks as you edit.

Is it free?

Yes, with no sign-up. Results are kept for 7 days; use “Check again” after you change the file.