Free llms.txt Validator - Score Your File & Get Found by AI

llms.txt is a plain Markdown file placed at the root of your website (e.g. https://yoursite.com/llms.txt) that gives AI language models a clean, structured guide to your site. AI tools like ChatGPT, Perplexity, Claude, and Google AI Overviews look for this file when deciding how to represent your content. A well-formed llms.txt helps AI models cite you accurately, understand what your site offers, and surface your pages in AI-generated answers - making it a key part of generative engine optimization (GEO).

The validator runs 10 checks against the official llmstxt.org specification: (1) H1 heading present, (2) blockquote description included, (3) at least one H2 section exists, (4) all links use correct Markdown format, (5) all link URLs are valid, (6) no duplicate URLs across sections, (7) Optional section usage when file is large, (8) link descriptions are under 200 characters, (9) file size and token count relative to AI context windows, and (10) site name is meaningful rather than a generic placeholder.

A score of 90 or above (grade A) means your file is excellent and fully spec-compliant. 75-89 (grade B) is good with minor improvements possible. 55-74 (grade C) means there are real issues affecting how AI models read your file. 35-54 (grade D) indicates significant structural problems. Below 35 (grade F) means the file has critical issues that need immediate fixing before AI models can use it. Aim for A or B before deploying.

Start with the highest-point failures first. Missing an H1 heading costs 10 points, a missing blockquote costs 10 points, and invalid link format costs 15 points - fixing these three alone can recover 35 points. The 'What to Fix' section below your score lists every failed or warned check with the exact change needed. Fix, then click Re-validate to confirm without re-entering your content. If you are starting from scratch, use the llms.txt Generator to build a fully valid file automatically.

Yes. Switch to the Fetch URL tab, enter any public URL ending in llms.txt, and the tool fetches and validates it. This is useful for benchmarking against industry leaders like Anthropic, Supabase, Cloudflare, Vercel, or Cursor - all of whom publish llms.txt files. Comparing your score to theirs shows exactly where you need to improve.

A 'fail' means a required element is completely missing or broken - for example, no H1 heading or invalid Markdown link syntax. These cost the full points for that check. A 'warn' means the element exists but does not fully meet best practices - for example, a link description that is slightly too long or a file size that is approaching AI context window limits. Warns cost partial points. Both appear in the 'What to Fix' section.

No. When you paste content or upload a file, validation runs entirely in your browser - no data is sent to any server. When you enter a URL, our server fetches only the text content of that URL to bypass browser CORS restrictions, but the content is never stored, logged, or processed beyond returning the raw text to your browser for client-side validation.

The llmstxt.org specification defines '## Optional' as a section for lower-priority pages that AI models can skip when they need a shorter context window. This validator only requires an Optional section when your file has more than 10 links AND is large enough to approach AI context window limits (roughly 125,000 tokens or more). If your file is small, Optional is recommended but not penalized. Large files without an Optional section force AI models to either read everything or nothing - the section gives them a smart middle ground.

The token count estimates how many tokens your llms.txt uses inside an AI model's context window, calculated as characters divided by 4. Green (under 125K tokens) means your file fits comfortably in all modern LLMs. Yellow (125K-180K) means you are approaching limits and smaller or older models may truncate your file. Red (above 180K) means your file is too large for many models. Keep your file green by using the Optional section for lower-priority pages and keeping link descriptions concise.

Validate every time you add new pages or sections to your site, update your site description, or change your URL structure. At minimum, run a validation once a month to catch any links that have gone dead or URLs that have changed. Treat your llms.txt like a sitemap - it should always reflect the current state of your site.