Complete llms.txt guide for 2026

Everything you need to know about llms.txt — what it is, where it came from, what AI models actually do with it, how to write one correctly, and the mistakes that quietly tank the whole exercise. What is llms.txt? llms.txt is a plain-text file you put at the root of your domain — at https://yoursite.com/llms.txt — that tells large language models what your site is about, which pages matter, and how to navigate it. It's written in Markdown. It's small. It exists for one reason: AI models have ve...