Free LLMs.txt File Validator
The most comprehensive online tool to validate your llms.txt and llms-full.txt files against the official standard. Ensure your website is AI-friendly and optimized for Large Language Models.
Enter the URL to your llms.txt or llms-full.txt file. The protocol (https://) will be added automatically if missing.
What is LLMs.txt?
llms.txt is a revolutionary proposed file standard that helps Large Language Models (LLMs) understand your website's structure and find your most important content efficiently.
📋 Quick Definition
/llms.txt is a Markdown file placed at your website's root directory that provides AI systems with a curated, structured overview of your site's most valuable content.
Think of it as: A navigation guide specifically designed for AI - just likerobots.txt guides web crawlers, but llms.txt guides intelligent AI systems.
AI-First Approach
Optimized specifically for LLMs and AI agents, not traditional search engines
Context Window Friendly
Clean, curated content that fits within LLM context limitations
Web Standard
Part of the emerging GEO (Generative Engine Optimization) movement
🤔 Why Does LLMs.txt Exist?
❌ The Problem
- • HTML pages cluttered with ads & navigation
- • Dynamic content confuses AI systems
- • Important content gets lost in noise
- • Context window limitations
✅ The Solution
- • Clean, curated content summaries
- • Structured Markdown format
- • Direct links to key pages
- • AI-optimized organization
Understanding LLMs-Full.txt
llms-full.txt is the companion file to llms.txt that containscomplete documentation content rather than just structured links.
📄 What Makes It Different?
While /llms.txt provides a structured index with links, /llms-full.txtcontains the actual content - full documentation, guides, and reference material in one comprehensive file.
Perfect for: AI systems that can process large contexts without needing to navigate multiple pages
🗂️ llms.txt (Index)
- ✓Structured format (H1, blockquote, H2 sections)
- ✓Links to important pages with descriptions
- ✓Small file size (<50KB typically)
- ✓Quick overview for AI navigation
📚 llms-full.txt (Content)
- ✓Free-form markdown content
- ✓Complete documentation in one file
- ⚠Large file size (can be >500KB)
- ✓Self-contained reference material
🤔 When Should You Use LLMs-Full.txt?
✅ Great For
- • Comprehensive API documentation
- • Complete user guides and tutorials
- • Technical reference materials
- • AI systems with large context windows
- • Self-contained documentation sites
⚠️ Consider Carefully
- • Files larger than 1MB (may hit limits)
- • Frequently changing content
- • Sites with many separate topics
- • Limited server bandwidth
- • Mobile or low-power AI systems
🔍 How Validation Differs
llms.txt Validation
- • Requires H1 header
- • Requires blockquote summary
- • Requires H2 sections with links
- • Strict structural rules
llms-full.txt Validation
- • Flexible content structure
- • Valid markdown format
- • File size warnings (>500KB)
- • Focus on readability
Note: Our validator currently applies llms.txt rules to both file types. This will be updated to use appropriate validation for each format.
Understanding LLMs.txt: The New Web Standard
What is llms.txt?
A proposed file placed at the root of your website (e.g., /llms.txt) in Markdown format to guide Large Language Models through your site's most important content in a clear, structured way.
Why does it exist? HTML pages are often cluttered with ads, navigation, scripts, or dynamic content. LLMs benefit from curated, plain-text summaries that fit their context window limits.
Similar to Other Web Standards
robots.txtControls web crawlers
sitemap.xmlLists site pages
llms.txtSignals to LLMs where to find important content
SEO vs GEO (Generative Engine Optimization)
Traditional SEO
Optimization for search engines like Google, Bing
New GEO
Optimization for LLMs and AI agents. llms.txt is a core GEO tool.
Why Proper LLMs.txt Validation Matters
Required Structure
# H1 HeaderPrimary site or project name
> Blockquote summaryConcise introduction for LLMs
## Section HeadersAt least one H2 section with links
Common Issues We Catch
Best Practices Our Validator Enforces
File Placement
Files must be accessible at /llms.txt and /llms-full.txt
Clean Structure
Proper H1, blockquote, H2 lists, and Optional sections
Current Content
All links should be valid and up-to-date
Size Management
Warning for files >500KB to ensure LLM context compatibility
Why Use an LLMs.txt Validator?
Ensuring your llms.txt file is correctly formatted is crucial for AI systems to understand and navigate your website effectively.
Prevent AI Errors
Malformed files can cause AI systems to misinterpret your content or miss important pages
Improve AI Discovery
Properly structured files help AI systems find and understand your most valuable content
Save Time
Catch errors instantly instead of debugging why AI can't understand your site
Stay Compliant
Ensure your file meets the official llms.txt standard specifications
Common LLMs.txt Mistakes to Avoid
❌ Missing Required Elements
- •No H1 header: Files must start with # Title
- •Missing blockquote: Summary must use > syntax
- •No H2 sections: At least one ## Section required
🔗 URL and Link Issues
- •Broken URLs: All links must be valid and accessible
- •Missing protocols: Use full URLs with http:// or https://
- •Duplicate links: Same URL appears multiple times
📏 Formatting Problems
- •Wrong Markdown: Incorrect heading levels or syntax
- •Bad list format: Links must be in - [Title](URL) format
- •Extra spaces: Inconsistent indentation or spacing
📦 File Size Issues
- •Too large: Files over 500KB may exceed AI context limits
- •Too many links: Keep under 100 links for efficiency
- •Redundant content: Focus on most important pages
LLMs.txt Best Practices Guide
📝 Content Structure
Do This ✅
- • Start with clear, descriptive H1
- • Write concise blockquote summary
- • Group related links under H2 sections
- • Add descriptions after links
- • Read our complete guide
Avoid This ❌
- • Generic titles like "Website"
- • Long, rambling summaries
- • Random link organization
- • Links without context
🎯 Link Selection
Include These Pages
- • Main documentation
- • API references
- • Getting started guides
- • Key features and benefits
Skip These Pages
- • Legal/privacy pages
- • Login/signup pages
- • Marketing landing pages
- • Outdated content
🔧 Maintenance Tips
- ✓Regular Updates: Review and update your llms.txt monthly to keep content fresh
- ✓Test Links: Validate all URLs periodically to catch broken links
- ✓Monitor Size: Keep file under 50KB for llms.txt, warn at 500KB for llms-full.txt
- ✓Version Control: Track changes to your llms.txt files in git
Frequently Asked Questions
What is llms.txt and why is it important?
llms.txt is a proposed file placed at the root of a website (e.g., /llms.txt) in Markdown format to guide LLMs through the site's most important content in a clear, structured way.
It exists because HTML pages are often cluttered with ads, navigation, scripts, or dynamic content. LLMs benefit from curated, plain-text summaries that fit their context window limits.
How is llms.txt similar to other web standards?
• robots.txt: controls web crawlers
• sitemap.xml: lists site pages
• llms.txt: explicitly signals to LLMs where and how to fetch important content
What's the difference between SEO and GEO?
SEO (Search Engine Optimization) optimizes for search engines like Google and Bing.GEO (Generative Engine Optimization) optimizes for LLMs and AI agents. llms.txt is a core tool for GEO.
Who is already using llms.txt?
Major projects: nbdev, FastHTML, LangGraph, LangChain, Fast.ai
Commercial support: Mintlify, Anthropic, Cloudflare, and Yoast (WordPress plugin)
What's the difference between llms.txt and llms-full.txt?
llms.txt: Contains structured links to your important pages with descriptions
llms-full.txt: A companion file that includes full plain-text content of documentation. Useful when LLMs can ingest large context without navigating individual pages, but may exceed context windows.
What are the best practices for llms.txt files?
• Place both files at root: accessible via /llms.txt and /llms-full.txt
• Maintain clean Markdown structure: H1, blockquote, H2 lists, "Optional" section
• Keep content current: regularly update as LLMs may access content frequently
• Mind size constraints: warn when /llms-full.txt is too large (>500 KB)
• Avoid broken links and duplicates to prevent parsing errors
Is this validator free to use?
Yes! Our llms.txt validator is completely free to use. No registration required, no limits on usage. We're committed to helping the web become more AI-friendly.