llms.txt Checker

What Is llms.txt?

llms.txt is a plain text file placed at the root of a website, for example, yoursite.com/llms.txt, that helps large language models (LLMs) and AI systems understand the site's structure and most important content.

Think of it as a curated, AI-readable index of your site. While sitemap.xml lists all your URLs for search engine indexing, llms.txt tells AI systems which pages matter most and what they contain, in plain language.

The format was proposed in 2024 and has quickly gained adoption as part of the broader GEO (Generative Engine Optimization) toolkit.

What This Checker Tests

When you enter a domain, this tool checks the following:

• File existence: Is there a file at /llms.txt on the root domain?
• HTTP status: Is it returning 200 OK? A 404 means no file exists.
• Content type: Is it served as text/plain as the spec recommends?
• H1 header: Does the file start with an H1 (site name) as required by the format?
• Description present: Is there a short description following the H1?
• Sections (H2): Are pages organized under H2 section headers?
• Linked entries: Does the file contain Markdown-formatted links with descriptions?
• llms-full.txt: Does the site also provide the optional full-text companion file?

The llms.txt Format

A valid llms.txt file follows this structure:

# Site Name

Brief 1-3 sentence description of what the site does and who it serves.

## Services

- [Service Page](https://example.com/services/): What this page covers.
- [Another Service](https://example.com/other/): Description.

## Blog / Guides

- [Key Article](https://example.com/article/): What this article covers.

## Tools

- [Free Tool](https://example.com/tools/tool/): What the tool does.

Use our free llms.txt Generator to build a properly formatted file for your site. For a complete guide to the format and strategy, read our llms.txt Complete Guide.

Why llms.txt Matters for AI Visibility

AI search platforms like ChatGPT, Perplexity, and Google AI Overviews retrieve and cite content from the web. The clearer and more structured your site appears to these systems, the more accurately and frequently they will reference your business.

llms.txt is part of a broader technical foundation for AI search visibility that includes:

• ✅ robots.txt, allowing AI crawlers to access your content
• ✅ Schema markup, structured data for entity and content verification
• ✅ llms.txt, curated navigation guide for AI systems
• ✅ Passage-level content: clear, extractable answer blocks

Use the AI Search Visibility Checker to get a comprehensive readiness audit that goes beyond just llms.txt.

Related Tools

• llms.txt Generator, Create a properly formatted llms.txt file for your site
• AI Search Visibility Checker, Full GEO readiness audit for your site
• AI Crawler Tester, Check which AI bots can access any URL
• Robots.txt Tester, Validate your crawler access rules
• Schema Markup Validator, Check your structured data
• Sitemap Checker, Validate your XML sitemap