llms.txt Validator
Ensure your AI-facing documentation is perfectly formatted. Fetch an existing file from a URL or paste raw Markdown to run a comprehensive validation audit.
Enter your domain (e.g. example.com) or direct file URL. We will automatically append /llms.txt if needed.
Analyzing Content...
How To Validate Your llms.txt
Input Data
Enter your root domain (e.g. example.com) to let our smart crawler find your file automatically, or switch tabs to paste your raw Markdown text directly.
Run the Audit
Click Validate. Our rules engine scans the Markdown against the community-accepted llms.txt specification for structural and syntax integrity.
Review & Fix
Review the red and green signal cards in the Validation Report. Use the visual Preview tab to ensure your file renders beautifully for AI parsers.
Premium Validator Features
Smart URL Resolution
You don't need the exact file path. If you type toolszu.com, our secure backend auto-formats the protocol and seamlessly checks https://toolszu.com/llms.txt.
Strict Spec Checking
The tool checks for crucial requirements: an H1 Title tag, a blockquote summary, linked documentation structure, and optimal file size limits for AI ingestion.
Instant Visual Preview
Markdown can be tricky to visualize. Our custom Formatted Preview tab instantly renders your raw text into styled HTML so you can spot formatting breaks easily.
Checklist for a Valid llms.txt File
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1. Proper Markdown Hierarchy
The file must begin with an H1 heading (
# Project Name) immediately followed by a brief blockquote (> Summary). This provides the AI agent with immediate context about your website. -
2. Absolute URLs Only
AI agents read this file as raw text, meaning they cannot resolve relative paths like
/docs/api. You must use full, absolute URLs (e.g.,https://example.com/docs/api) for all links. -
3. Root Directory Placement
To comply with the community specification, your file must live at the top-level root of your domain (
https://yourdomain.com/llms.txt), making it predictably discoverable by automated scrapers. -
4. Correct Content-Type Header
Your web server must serve the file with a
text/plainortext/markdownHTTP header. Serving it astext/htmlcan trigger errors in strict AI parsers. -
5. Optimized File Size
Keep it concise. The file should act as a structural map, not a dump of all your website's text. Files over 100KB risk exceeding an LLM's initial context window.
Frequently Asked Questions
Large Language Models (like ChatGPT or Claude) have strict context window limits. If your llms.txt file is massive (e.g., over 100KB), it wastes valuable AI tokens. Your file should act as a concise directory or sitemap that links out to your actual documentation, rather than containing the entire contents of your website.
According to the official llms.txt specification, the very first line of your file must be a Markdown H1 tag containing the name of your project. Ensure you start the document with # Your Project Name. Note that a space between the hashtag and the text is strictly required in Markdown.
You must use absolute URLs. Because AI agents are parsing a raw text file and not rendering a webpage in a browser, they cannot resolve relative paths like /api/docs. Always write out the full URL: https://yourdomain.com/api/docs.
Your web server must serve the llms.txt file as plain text (text/plain) or markdown (text/markdown). If the fetch tool detects text/html, it usually means your server is returning a custom 404 HTML error page, or a firewall (like Cloudflare) is blocking the bot request.
No. robots.txt and llms.txt serve entirely different purposes and use different syntax (Plain Text directives vs. Markdown). If you need to generate or check your crawler directives, use our dedicated Robots.txt Generator.