What is llms.txt and does your website need one?

Last updated 10 October 2026 · By the XKey team

Where llms.txt came from

The format was proposed in September 2024 by Jeremy Howard of Answer.AI. The idea: web pages are full of menus, adverts and scripts that large language models (LLMs) have to wade through. A plain Markdown file at yourdomain.co.uk/llms.txt could give them a clean summary instead – who you are, what the site covers and links to the pages that matter.

What goes in the file

A typical llms.txt has:

• a heading with your site or business name,
• a one-line summary in a quote block,
• a short paragraph with any important context, and
• sections of links, each with a few words about the page – for example your services, prices, guides and contact page.

You can see XKey's own at xkey.co.uk/llms.txt, or build yours in a minute with the llms.txt generator.

Does Google use it?

No – not for Search. Google's Search guidance says you don't need llms.txt or any other special file to appear in AI Overviews or AI Mode; those features draw on the normal search index, so ordinary SEO is what counts. Other parts of Google take a different view: in 2026 Lighthouse added an experimental check for llms.txt as part of assessing whether sites are ready for AI agents browsing on people's behalf.

Do ChatGPT, Claude or Perplexity use it?

None of the big AI companies has published a commitment to read llms.txt when deciding what to cite. Some AI coding tools and documentation sites do use it, and AI agents may fetch it when they're sent to explore a site. In short: there's no evidence it boosts your visibility today, and no evidence it does any harm.

So should you add one?

If it takes you ten minutes, yes – it's a tidy summary of your site, it costs nothing and it may become more useful as AI agents spread. But it is not a replacement for the things that demonstrably matter for AI search:

• letting AI search crawlers in through robots.txt (see our guide to blocking training bots without leaving AI search),
• clear Organization or LocalBusiness schema markup,
• pages that answer real questions directly, and
• being indexed by Google and Bing in the first place.

The AI SEO checker tests all of these, including whether you have an llms.txt file, and weights them by how much they really matter.

Frequently asked questions

Is llms.txt the same as robots.txt?

No. robots.txt tells crawlers which pages they may visit. llms.txt is a summary and reading list; it doesn't allow or block anything.

Where does the llms.txt file go?

In the root of your website, so it loads at yourdomain.co.uk/llms.txt – the same place as robots.txt.

What is llms-full.txt?

An optional companion file containing the full text of your key pages in Markdown. It's mainly used by software documentation sites and isn't needed for most businesses.