Free Tools/llms.txt Validator

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llms.txt Validator

Check any domain's llms.txt against the real spec, missing title, broken links, relative URLs, and the other mistakes that stop an AI assistant using it properly.

Why use our llms.txt Validator

Instant validation, no manual review

Enter a domain and get every structural issue in your llms.txt flagged in seconds, no need to read the spec and check line by line yourself.

Free llms.txt checker, no signup

Validate llms.txt structure online for free, with no account required, unlike enterprise AI-SEO monitoring platforms.

Catches AI-crawler-breaking errors

Flags missing H1 titles, relative URLs, and broken links, the exact mistakes that stop ChatGPT, Claude, and Perplexity from parsing your file correctly.

Clear pass/fail issue list

See errors and warnings separated and labelled, so you know exactly what's critical to fix versus what's just a best-practice suggestion.

Website domain *

What this checks

A single H1 title, first in the file: The spec requires the very first line to be `# Your Site Name`. Content or extra H1s before it are flagged.

A summary blockquote right after the title: Not required, but it's the first thing AI tools read about your site: a `>` line straight after the H1.

Well-formed links in every section: Each H2 section should hold a markdown list of `[title](url): notes`. Broken syntax, missing URLs, and empty sections are flagged.

Absolute URLs, no duplicates: Relative paths force an AI tool to already know your domain to resolve them; repeated URLs are usually a copy-paste mistake.

Real llms.txt Validator example: before vs. after

A real llms.txt file with a structural mistake vs. the same file fixed to pass validation.

Before · Fails validation

Acme Analytics is a web analytics platform.

## Docs
- docs/getting-started: setup guide
- API Reference: /docs/api

Missing the required H1 title line, and links use relative or malformed paths, exactly the structural errors that stop AI crawlers from parsing the file.

After · Passes validation

# Acme Analytics

> A web analytics platform for privacy-focused teams.

## Docs
- [Getting Started](https://acme.com/docs/getting-started): Setup guide
- [API Reference](https://acme.com/docs/api): Full endpoint list

Has a proper H1 title, a blockquote summary, and full absolute URLs in every link, the structure most llms.txt parsers expect.

Frequently Asked Questions

What does an llms.txt validator actually check?

It checks whether your llms.txt file follows the correct plain-text Markdown structure, an H1 title, an optional blockquote summary, and H2-organised link sections, the format most llms.txt parsers and AI crawlers expect. It flags structural errors that could stop the file from being read correctly.

My llms.txt file exists but isn't being read correctly, why?

The most common causes are: it's not at your domain root (must be yourdomain.com/llms.txt exactly), it's missing the required H1 title line, or the file isn't served as plain text. Run it through the validator to see exactly which structural rule is failing.

Is there an official llms.txt validation standard?

Not an official one, llms.txt is a proposed, community-driven convention, not a ratified web standard. This tool validates against the commonly agreed structure most implementations follow, since there's no single authoritative spec to check against yet.

Should I validate llms.txt the same way I'd validate robots.txt?

The goal is similar, catching structural mistakes before they matter, but the rules are different. Robots.txt validation checks crawl directives syntax. llms.txt validation checks Markdown structure and required sections, since it's a content summary format, not an access-control file.

Preparing your pages for AI assistants? Turn any page into clean Markdown with our HTML to Markdown Converter.

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