Answer
What is llms.txt and do I need one?
Last updated
Short answer
llms.txt is a plain-text Markdown file placed at the root of your domain (yoursite.com/llms.txt) that gives AI models a concise, curated map of your most important factual pages. It works like a sitemap written for large language models, and it is one of the fastest technical AEO wins available because it removes guesswork about what your business is and which pages state your facts.
What it is, precisely
A single UTF-8 Markdown file served as text/plain at /llms.txt. It opens with an H1 naming your business, a short blockquote summary, then linked sections grouping your key pages with one-line descriptions of each.
It is not a ranking mechanism and it is not a directive file like robots.txt. It is a curation hint: here is who we are, and here are the pages where our facts live.
What belongs in it
Facts, not marketing. The value of the file is that everything in it can be relied on.
- Business name, one-sentence description, and what you sell
- Service area, hours, phone number and email exactly as they appear elsewhere
- Links to your key factual pages - services, pricing, FAQ, about, contact
- Pricing, if you publish it, stated the same way as on your pricing page
- A last-updated date so a model can judge freshness
llms.txt versus llms-full.txt
llms.txt is the index. llms-full.txt is the optional expanded companion containing the actual content - full FAQ text, definitions, complete policy statements - so a model can consume your facts without crawling every page.
If you have a substantial FAQ or glossary, publishing both is worth it: the index tells a model where to go, the full file means it does not have to.
Do you actually need one
It is not yet a universal standard, and no engine has published a guarantee that it reads the file. What is true is that it costs almost nothing to publish, it cannot hurt, adoption is growing, and the exercise of writing it forces you to make your facts consistent - which helps regardless of whether any specific crawler parses it.
The honest framing: low cost, plausible upside, and a useful forcing function. That is why every MyFast AI audit generates one customized from your own results.
How to check yours is live
Open yoursite.com/llms.txt in a browser. It must return HTTP 200 and render as plain text, not download as a file and not return your 404 page. Then confirm the facts inside match your site, your Google Business Profile and your other listings exactly.
Frequently asked questions
Where does llms.txt go?
At the root of your domain: https://yoursite.com/llms.txt. It must return HTTP 200 with a text/plain content type.
Does llms.txt replace robots.txt or sitemap.xml?
No. robots.txt controls crawler access, sitemap.xml lists every indexable URL, and llms.txt curates the small set of pages that state your facts. They serve different purposes and you should have all three.
Do AI engines definitely read llms.txt?
No engine has published a commitment to it, so anyone claiming certainty is overstating. It is cheap, harmless and increasingly common, which is why it is worth publishing.
Related reading
Written by Benjamin Heckendorf, Founder & CEO of MyFast.ai.
Find out what AI says about your business
Run 100 real buyer searches across all seven engines and see exactly where you are named, cited or missing. First report $99.