What Is llms.txt?
llms.txt is a plain Markdown file placed at the root of a website, at /llms.txt, that gives large language models a short, curated guide to the site: what it is about and which pages are worth reading. The idea was proposed in 2024 by Jeremy Howard of Answer.AI and is documented on the project's own site, llmstxt.org.
The problem it targets is practical. A normal web page is built for browsers, so the text a model actually needs sits between navigation menus, cookie banners, scripts, footers and ads. When an AI assistant or agent fetches a page to answer a question, all of that noise competes for a limited context window. Site owners, on the other hand, already know which pages explain their product best. llms.txt lets them say so in one small file, with a sentence of context next to each link.
Think of it as a hand-written table of contents for machines. It does not list every URL the way a sitemap does, and it does not grant or block access the way robots.txt does. It simply points a reader that has already arrived toward the material you consider most useful.
Its status matters. llms.txt is a proposal, not a ratified web standard. No standards body maintains it, no AI company is obliged to read it, and support varies from tool to tool. Adopting it is voluntary and cheap: one text file, no code, no change to your existing pages. That low cost is why many documentation sites, developer tools and publishers have added one, and why it is worth understanding what the file can and cannot do before you write yours.