What Is llms.txt?

llms.txt is a plain text file, written in markdown, that sits at the root of your website and gives AI systems a curated summary of what your site is about and where your most important content lives. Think of it as a welcome guide for large language models: where robots.txt tells crawlers what they may not touch, llms.txt tells AI tools like ChatGPT, Claude and Perplexity what they should read first.

It is a proposed standard rather than an official one, but it is gaining traction fast as AI search grows. Here is what the file contains, whether it actually matters, and how to create an llms.txt file for your own site.

What Exactly Is an llms.txt File?

The llms.txt specification proposes a simple markdown file at yoursite.com/llms.txt. A typical file includes the site name, a short description of what the business does, and a structured list of important URLs with one-line summaries of each. Because it is markdown, it is machine-readable and human-readable at the same time.

The logic behind the format is a real constraint: large language models work with limited context windows. They cannot read your whole website when composing an answer, so a compact, structured summary of your site's content gives them exactly what they need in the form they parse best. Some sites go further with an llms-full.txt, which packs full page content into one markdown file for AI systems that want depth rather than a map.

llms.txt vs robots.txt vs sitemap.xml

These three files are cousins with different jobs. robots.txt is about permission: which bot may crawl which URL. sitemap.xml is about completeness: a machine-readable list of every URL you want indexed by search engines. llms.txt is about understanding: a curated, prioritised guide that tells AI models which content matters most and what it means. A well-run site in 2026 has all three, and they do not conflict.

Does llms.txt Actually Improve AI Visibility?

Honest answer: adoption is early and uneven. Not every LLM reads the file yet, and no AI company has committed to it the way search engines committed to sitemaps. Anyone telling you llms.txt is a guaranteed visibility switch is ahead of the evidence.

Here is the practical case for doing it anyway. The file takes an hour to create. It cannot hurt you. And the direction of travel is unmistakable: a growing share of buying research now happens inside ChatGPT, Perplexity and Google's AI Overviews rather than classic search results, and brands that are easy for AI to understand and cite will collect that visibility. Being early to llms.txt is a cheap bet with real upside, the same bet early adopters of schema markup made years ago and won. At Rank Craft we implement llms.txt as standard within our GEO service, alongside schema and the content structure work that AI systems reward. This site has one too, at rankcraft.co.uk/llms.txt, so you can see a live example.

How to Create an llms.txt File

You can write one in any text editor. The structure looks like this:

• Title and summary first. An H1 with your site name, then a short blockquote describing what you do, who you serve and what makes you credible.
• Then sections of links. H2 headings such as Services, Guides or About, each containing a markdown list of your key URLs with a one-line description per link.
• Keep it curated. This is not a sitemap dump. Twenty well-chosen URLs with sharp descriptions beat two hundred bare links, because the file's whole job is prioritisation.

Save it as llms.txt, upload it to your site root, and check it loads at yoursite.com/llms.txt as plain text. Update it whenever your key pages change, the same way you would a sitemap. There are llms.txt generator tools around, but for most businesses hand-writing it produces a sharper file, because the descriptions are where the value lives.

The Bigger Picture: llms.txt Is One Piece of AI Search

A file alone does not earn citations. AI assistants recommend brands whose content is genuinely useful, clearly structured, marked up with schema, and referenced by other credible sites. That wider discipline is called generative engine optimisation, or GEO, and llms.txt is simply its cheapest first step. If you want to know how visible your brand currently is in AI answers, and what it would take to improve, our GEO specialists run exactly that audit. You can also read our guide to Google E-E-A-T, because the trust signals that win featured snippets are the same ones AI models weigh when choosing who to cite.

Frequently Asked Questions

Is llms.txt the same as robots.txt?

No. robots.txt controls which crawlers may access your site. llms.txt does the opposite job: it is a curated guide that helps AI systems find and understand your most important content. One restricts, the other assists.

Do all AI companies use llms.txt?

Not yet. llms.txt is a proposed standard and adoption is still uneven. Some AI tools read it, others ignore it. The cost of adding one is an hour of work, so most SEO professionals treat it as a cheap bet on where AI search is heading.

Does llms.txt replace SEO?

No. llms.txt sits alongside SEO. AI assistants still lean heavily on classic signals like content quality, structure and authority. A well-optimised site with an llms.txt file is the combination that wins visibility in both Google and AI answers.