The llms.txt format

An llms.txt file has one H1 with the site name, an optional blockquote summary, optional free text, and H2 sections that each hold a list of Markdown links with a one-line description. That is the entire structure defined by the llms.txt proposal at llmstxt.org. Everything else on this page is about doing those parts well.

What is the basic skeleton?

# Site name                    <- H1, required, exactly one

> One or two sentence summary. <- blockquote, optional, strongly recommended

Optional free text paragraph explaining anything the summary could not.

## Section name                <- H2, defines a section
- [Page title](https://example.com/page): One-line description.
- [Another page](https://example.com/other): One-line description.

## Optional                    <- a convention for secondary links
- [Lower priority page](https://example.com/archive): Background reading.

The H1

Exactly one, at the top, giving the name of the site or organisation. Parsers take the first H1 as the file’s title; a second one is ambiguous and a file with none is malformed. Use your real brand name, not a keyword-stuffed variant.

The blockquote summary

Technically optional, in practice the most valuable line in the file. It is the part most likely to be read in full and quoted back. Use one or two sentences covering what you do, who for, and any qualifier that prevents a wrong assumption: where you operate, what you do not sell, who you are not for.

> Independent supplier of woodworking hand tools, based in Leeds. We sell,
> sharpen and restore. UK shipping only; we do not sell power tools.

Note the last clause. Telling a model what you are not prevents a whole class of confidently wrong answers.

Sections

H2 headings group related links. Use the words your visitors use (Products, Documentation, Pricing, Support, Guides) rather than internal department names. H3 and deeper are not treated as section boundaries, so keep the hierarchy flat.

How should each link be written?

Every entry is a Markdown list item in one shape:

- [Link text](absolute URL): Description.

How long should a description be?

One sentence, roughly ten to twenty-five words, and specific. The test is whether the description would let a model answer a simple question without opening the page. “Our pricing options” fails. “Three plans from USD 12 to USD 79 per user per month, billed annually” passes.

What is the Optional section for?

A section headed ## Optional is the conventional home for links that are useful but secondary: company history, changelogs, old announcements, legal pages. In the original proposal it told context-building tools what they could leave out. the V2 change notes for V2 dropped that mechanical meaning, so it is now simply a clear label for background material. It still reads best at the end of the file.

How must the file be served?

• At /llms.txt on the domain root, which every reader checks. Under V2 a file in a subdirectory also works and covers the pages beneath it; the most specific file applies. Each subdomain needs its own.
• Content type text/plain or text/markdown, never text/html.
• UTF-8, ideally without a byte order mark.
• An HTTP 200 directly. A redirect chain is followed by some readers and not others.
• Not blocked by your own robots.txt, which happens more often than you would expect.

V2 also adds two optional links your pages can carry: rel="describedby" pointing at the llms.txt that covers them, and rel="alternate" type="text/markdown" pointing at a Markdown version of the page. The V2 guide has the markup. The validator checks serving against a live URL.