llms.txt Checker

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Check if any website has a valid llms.txt file. Verify existence, format, structure, and completeness — the AI-readable index that helps ChatGPT, Perplexity, and other AI systems understand your site.

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.

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llms.txt Checker: FAQ

What is llms.txt?
llms.txt is a plain text file placed at the root of a website (e.g. yoursite.com/llms.txt) to help large language models and AI systems understand the site's most important content, structure, and purpose. It acts as a curated index designed specifically for AI consumption, complementing robots.txt and sitemap.xml.
What does this llms.txt checker test?
This tool fetches the llms.txt file from any domain you enter and checks: whether the file exists and is accessible, whether it follows the correct Markdown format, whether it has an H1 site name, a description, and organized sections with linked entries. It flags missing required elements and structural issues.
Is llms.txt required for AI search visibility?
It is not strictly required, but it is recommended for sites that want to improve GEO (Generative Engine Optimization) performance. llms.txt gives AI systems a clear, curated entry point to your best content. Sites that provide this guidance are better positioned as AI crawler support for the format grows.
What is the correct format for llms.txt?
An llms.txt file uses Markdown formatting. It should start with an H1 header (the site name), followed by a short description, then H2 sections organizing linked page entries. Each entry should be a Markdown link with a brief description: [Page Title](https://example.com/page/): What this page covers.
What is the difference between llms.txt and llms-full.txt?
llms.txt is a curated navigation index — it lists your most important pages with short descriptions. llms-full.txt is an optional companion file that contains the full text of key pages concatenated together, for AI systems that want comprehensive content in a single file. Most sites should start with llms.txt.
Does robots.txt affect whether AI can read llms.txt?
Yes. If you block AI crawlers in your robots.txt, they cannot read your llms.txt either. Make sure your robots.txt allows relevant AI crawlers (GPTBot, PerplexityBot, ClaudeBot) to access your site, including the llms.txt file. Use our Robots.txt Tester to check your current crawler access settings.
How do I create an llms.txt file?
Use our free llms.txt Generator to build a properly formatted file in minutes. List your key pages organized by category, add brief descriptions, and place the file at your site root. The file should be served as plain text (Content-Type: text/plain).
Is this llms.txt checker free?
Yes. Completely free, no signup, no limits. Enter any domain and get an instant check of whether it has a valid, well-formed llms.txt file.

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