llms.txt Tester and Validator
“Just create an llms.txt, throw in a few lines, and you’re done!” – Unfortunately, it’s not quite that simple. Even though the llms.txt file isn’t an official standard yet, there are clear structural rules that should be followed so AI systems can correctly interpret your content.
This tool checks your llms.txt file for compliance with the llms.txt specification: structure, formatting, heading hierarchy, and optional sections. You can also test the reachability of all linked URLs – so you can be sure there are no dead links in your file.
LLMS.txt Validator
Validate llms.txt files for compliance with the llms.txt specification.
Enter a domain to fetch and validate its llms.txt file.
Paste your llms.txt content below. Validation happens automatically as you type.
Upload a .txt file to validate its contents.
The validation result will be displayed here.
How the llms.txt Validator Works
- Enter a domain: Enter your domain, and the tool automatically fetches the file stored at
/llms.txt. If anllms-full.txtexists, that’s noted as well. - Paste content: Alternatively, copy the contents of your llms.txt file directly into the text field. Validation starts automatically as you type.
- Upload a file: You can also upload a .txt file from your computer.
- Read the results: The tool shows the validation status, specific error messages (e.g., missing H1 heading, incorrect heading order), and optimization suggestions.
- Enable link check (optional): Check the “Check URL reachability” option to test every link in your file via HEAD request.
What Gets Checked?
- Structure validation: The first line must be an H1 heading. H2 sections must follow after the H1. No duplicate H1 entries.
- Markdown format: Correct use of headings (
#,##), links, and blockquotes. - Optional sections: Detection of recommended areas like
## Optionalfor additional resources. - Link reachability: Status check of all absolute URLs with detection of redirects, WAF blocks, and server errors.
Changelog
- Added link reachability check via HEAD request with per-link status display (reachable, redirect, error, WAF block)
- Integrated llms-full.txt detection for domain queries
- Added optimization suggestions (“Add a blockquote summary after the title,” “Add an Optional section”)
- Implemented cancel function for running link checks
- File upload as a third input option alongside domain query and text entry
Background: Why an llms.txt File Matters
The llms.txt file is a proposal that allows website operators to curate their content specifically for Large Language Models (LLMs). While robots.txt controls which pages may be crawled, llms.txt describes which content is relevant for AI systems and how it’s structured for retrieval.
What Is the File For?
More and more AI systems – from ChatGPT to Claude to Perplexity – browse websites to answer user questions. The llms.txt gives these systems a curated overview of your most important pages, organized by topic and priority. This lets you actively influence which content AI applications use as the basis for their answers.
What Should You Do With the Results?
- Fix errors: Structural errors like a missing H1 heading or incorrect heading order prevent AI systems from correctly parsing your file.
- Repair dead links: If the link check finds broken URLs, update or remove them.
- Implement optimization suggestions: A blockquote summary after the title helps AI systems grasp your website’s purpose at a glance.
Frequently Asked Questions
What is an llms.txt file?
The llms.txt is a Markdown file in your website’s root directory (at /llms.txt) that gives Large Language Models a structured overview of your most important content. It contains a main heading, an optional summary, and thematically grouped links.
Is llms.txt an official standard?
No, it’s currently a community proposal. The specification is maintained at llmstxt.org. Even without official status, the file is already recognized by several AI providers.
What’s the difference between llms.txt and llms-full.txt?
The llms.txt contains links and a compact overview. The llms-full.txt can contain the full content of your website in text form – useful for AI systems that need the entire context without fetching individual pages.
Do I need an llms.txt if I already have a robots.txt?
Yes, both files serve different purposes. The robots.txt controls which pages may be crawled. The llms.txt recommends which pages are relevant for AI systems. They complement each other.
What does a WAF block mean in the link check?
A WAF (Web Application Firewall) like Cloudflare can block automated requests. If a link is marked as “WAF block,” the page is likely reachable, but the firewall rejected the test request. This isn’t an error in your llms.txt – the URL itself is typically correct.
How many links should an llms.txt contain?
There’s no fixed limit, but focus on your most important pages. A well-curated file with 10–30 links is usually more effective than a complete sitemap. Use H2 sections to create thematic groups.
