Free tool
llms.txt validator
Paste an llms.txt file and see it checked against the proposal’s own format rules: the heading, the summary, the sections and every link, with each fault named by line and the file’s outline drawn beside it. Nothing you paste leaves your browser.
Crawl and AI access files are part of the first pass in our technical SEO services.
Open your-site.com/llms.txt in a new tab, select all, and paste it here.
Result
Paste a file to check it. This needs scripting on.
Outline
What was checked
The rules it checks, from the proposal
The format is set out at llmstxt.org, in the second version of Jeremy Howard’s proposal, modified on 10 August 2026. A file has these parts, in this order:
- An optional byte-order mark, which the validator ignores.
- An H1 with the name of the site. The proposal calls this the only required section.
- A blockquote with a short summary of the site.
- Any number of paragraphs or lists, of any kind except headings.
- Any number of sections under H2 headings, each a list of entries. Each entry is a required Markdown link, [name](url), then optionally a colon and notes.
A section headed Optional is, by convention, the links an agent can skip when it needs a shorter context. Faults are things the proposal rules out. Notes are things it does not rule on but that cause trouble, such as relative addresses and links with no notes.
The faults it finds most often
- An HTML page instead of a text file. The address answered with the site’s 404 page or home page. Every line fails, and the fix is on the server: the file is missing or a rewrite rule is catching it.
- No H1, or the H1 is not first. A file that starts with a comment, a date or a blank heading. The name has to come first.
- Headings before the first section. An H3 used as a sub-heading in the summary area. The proposal allows any markdown there except headings.
- Broken links. A space between the brackets and the parentheses, a missing closing bracket, or a bare address with no name. Each entry needs [name](url).
- Pages that no longer exist. The validator cannot open your links, so check the list against your sitemap. A file that names deleted pages is worse than no file, which is why ours is generated from the same route map as the sitemap.
Whether you need the file at all
This page checks the format and makes no claim for the file. Google says you do not need AI text files to appear in AI Overviews or AI Mode, and the llms.txt example sets out what the proposal and the vendors each say, with a live file to compare against. The files that do decide what AI crawlers may read are robots.txt, which the robots.txt generator writes, and the firewall in front of the site, covered in the ChatGPT SEO guide. To see whether assistants name your business at all, use the AI visibility checker.
If you would rather hand the whole crawl and indexing layer over, that is our technical SEO service.
Questions about validating llms.txt
What does the validator check?
The rules in the proposal at llmstxt.org: an H1 with the site’s name, which is the only required part; a blockquote summary; no headings before the first H2; and under each H2 a list of entries, each a Markdown link with an optional colon and notes. It also flags what usually goes wrong in practice: an HTML page served in place of the file, broken link syntax, relative or duplicate addresses, and empty sections.
Can it check the file on my website directly?
Not from this page. A browser will not let one site read a file from another site unless that site allows it, so open your-site.com/llms.txt in a new tab, select all, and paste it here. The button that loads a file only reads this site’s own llms.txt, as a working example.
My file passes. Will AI assistants read it now?
The validator checks the format and nothing more. Google’s documentation on AI features says you do not need AI text files to appear in AI Overviews or AI Mode, and no assistant’s documentation we could find says it fetches llms.txt when it answers. The llms.txt example page sets out what each side says.
Are relative links allowed?
The proposal shows full addresses in its examples and does not rule on relative ones. A reader that resolves them against the file’s own address will cope; one that does not will not. Full addresses starting with https work for every reader, so the validator suggests them.
Is anything I paste sent anywhere?
No. The check runs in your browser. The only request the page can make is to this site’s own llms.txt, and only when you press the button that loads it.
Book a call with us
A 30-minute call in your working hours. Tell us what you sell and where, and we will tell you what we would do first and what it involves. Prefer email? Send your website through the form and the Passieon Team will reply within two working days.