There's a new file showing up at the root of well-built websites: llms.txt. Where the old robots.txt tells search crawlers what to skip, llms.txt does the opposite job for AI systems — it hands ChatGPT, Claude, and their cousins an organized briefing on who you are and which pages matter. Small file, surprisingly large implications.
What it is, concretely
llms.txt is a plain markdown file at the root of your website (yoursite.com/llms.txt). It contains a short description of who you are, followed by organized links to your key pages with one-line summaries. Some sites add a companion, llms-full.txt, carrying the complete site content in one machine-readable page — so an AI system can understand everything you offer without crawling dozens of pages.
Why it exists
AI assistants work under tight constraints: limited context, limited time per answer. When someone asks ChatGPT or Claude for a recommendation, the systems favor sources they can read quickly and trust. A clean llms.txt is the difference between an AI parsing your homepage's navigation soup and being handed an organized briefing about your business.
Does it actually matter yet?
Honest answer: it's early. llms.txt is a young convention, and no AI company guarantees they'll read it. But the cost is nearly zero, the downside is nonexistent, and the direction of travel is unmistakable — a growing share of buying decisions start as questions to an assistant instead of searches. The sites that are machine-readable early tend to become the sources those systems keep citing. It's the cheapest bet in marketing.
What it doesn't replace
llms.txt complements the fundamentals, it doesn't replace them: structured data (schema markup) on every page, semantic HTML, real answers written in plain language, and a robots policy that doesn't accidentally block AI crawlers. If those basics are missing, start there — llms.txt is the garnish, not the meal.
How to add one
For a small site, you can write one by hand in any text editor and upload it to your site root. The better version is generated: our builds create llms.txt and llms-full.txt automatically from the site's actual content, so they update themselves whenever the site changes and can never drift out of date. However you do it, the test is simple — visit yoursite.com/llms.txt and read it as if you were an assistant meeting your business for the first time. Would you know who to recommend?