llms.txt is a markdown file published at the root of a website that gives large language models a short, curated map of the site. The specification at llmstxt.org defines its structure: an H1 with the project or site name, a blockquote summary, optional heading-free detail blocks, and H2 sections containing file lists of the form - [name](url): optional notes.

Where does the llms.txt file have to be located?

At the root of your domain, served at yourdomain.com/llms.txt. The specification also describes a companion file, /llms-full.txt, which holds the expanded content itself instead of an index of links. This checker looks for both when you validate by URL.

What does this llms.txt checker validate?

Five structural rules drawn from the specification: that the file is markdown using only H1 and H2 headings, that it opens with a single H1 project title, that a blockquote summary follows it, that any further detail blocks contain no headings, and that each H2 section contains a file list of link items. Each rule is weighted, and the total becomes a score out of 100 with a letter grade.

Is the blockquote summary required in llms.txt?

The H1 with the project name is the only section the specification marks as required. The blockquote summary is described as part of the expected structure and carries the key information needed to understand the rest of the file, so this checker treats a missing summary as a problem worth fixing rather than a hard failure of the format.

What does the Optional section mean in llms.txt?

A section named exactly Optional has special meaning in the specification: the URLs listed under it may be skipped when a shorter context is needed. Use it for secondary pages such as contact, legal and policy pages, and keep it as the last section in the file.

What is the difference between llms.txt and llms-full.txt?

llms.txt is a compact index — a title, a summary, and lists of links to the pages that matter. llms-full.txt is the companion convention that contains the full content itself in one file, for cases where a model should read the material rather than follow links to it.

Does llms.txt replace robots.txt or a sitemap?

No. robots.txt tells crawlers what they are allowed to fetch and a sitemap lists every indexable URL. llms.txt does neither — it is a curated summary that tells a language model which content is worth reading and how the site fits together. They serve different purposes and can all coexist at the site root.

Do I need an account to use this llms.txt checker?

No. The checker is free and requires no sign-up. You can validate a live URL or paste the contents of a draft file, and the results are returned to you without being published anywhere.

Free llms.txt validator

llms.txt Checker

Validate any llms.txt file against the official llmstxt.org specification

Paste a URL or the raw file and this checker parses it the way an AI crawler would — confirming the markdown structure, the required H1 title, the blockquote summary, the detail blocks and every H2 file list, then telling you exactly which line to fix.

Free

No sign-up

Follows the llmstxt.org spec

URL or pasted content

What is llms.txt?

llms.txt is a markdown file published at the root of a website — yourdomain.com/llms.txt — that gives large language models a short, curated map of the site. Instead of asking a model to crawl navigation, scripts and boilerplate, the file hands it a title, a summary and a list of the pages that actually matter.

The format is defined by the specification at llmstxt.org. It is deliberately small: only H1 and H2 headings exist, and the body of each section is a list of links. That constraint is what makes the file both human-readable and trivially parseable by a program.

The spec also describes a companion convention, /llms-full.txt, which contains the expanded content itself rather than an index of links.

The required order, per the spec

1An optional byte-order mark at the very start of the file.
2An H1 with the name of the project or site — the only required section.
3A blockquote with a short summary containing the key information needed to understand the rest of the file.
4Zero or more markdown blocks — paragraphs, lists, tables — of any type except headings.
5Zero or more sections delimited by H2 headers, each containing a file list of `- [name](url)` items with optional `: notes`.
6A section named exactly “Optional” has special meaning: its URLs may be skipped when a shorter context is needed.

The 5 validation rules we check

Every check maps directly to a clause in the llmstxt.org specification. Each rule is scored, and the weighted total becomes your compliance score and letter grade.

Markdown format

markdown-format

The file must be markdown, and only H1 and H2 headings exist in the format.

Serve plain markdown at /llms.txt — no HTML, no YAML front-matter, no H3–H6 headings. Anything deeper than an H2 is outside the specification.

H1 project title

h1-title

An H1 with the name of the project or site. This is the only required section.

Start the file with a single `# Your Site Name` line. It is the one part of the spec that is mandatory, and there should be exactly one of them.

Blockquote summary

blockquote-summary

A blockquote with a short summary of the project, containing key information necessary for understanding the rest of the file.

Put a `> one-paragraph summary` directly under the H1. Say what the site is and who it serves, so a model can interpret every link below it.

Detail blocks without headings

project-details

Zero or more markdown sections (for example paragraphs, lists, tables) of any type except headings, containing more detailed information.

Add optional context after the summary as paragraphs, lists or tables. Do not use a heading here — the next heading in the file should be your first H2 section.

H2 sections with file lists

file-lists

Zero or more markdown sections delimited by H2 headers, containing file lists of URLs where further detail is available.

Group links under `## Section name` headings, one link per line as `- [Name](https://absolute-url): optional notes`. A section named exactly `Optional` may be skipped when a shorter context is needed, so keep it last.

How to write a compliant llms.txt

Implementation guide

Six decisions that keep the file inside the spec.

1Open with one H1. Use your site or project name — nothing above it except an optional byte-order mark. This is the only section the spec requires.
2Add the blockquote summary. One `>` paragraph directly under the H1 explaining what the site is, so the links below have context.
3Keep detail blocks heading-free. Extra paragraphs, lists or tables are allowed after the summary — but no headings until your first H2.
4Group links under H2 sections. Name sections after what a model would look for: Docs, Guides, API, Blog. Only H1 and H2 exist in this format.
5Write file-list items exactly. `- [Page name](https://example.com/page): short note`. Use absolute URLs so a model can resolve them without a base URL.
6Put “Optional” last. A section titled exactly Optional may be skipped when a shorter context is needed. Reserve it for secondary pages and keep it at the end.

The spec template

The canonical example published at llmstxt.org — copy it and fill in your own values.

# Title

> Optional description goes here

Optional details go here

## Section name

- [Link title](https://link_url): Optional link details

## Optional

- [Link title](https://link_url)

Save it as llms.txt and upload it to your site root so it is served at yourdomain.com/llms.txt, then run it back through this checker.

How to use this checker

1
Pick an input mode
Choose Check by URL to validate a file that is already live, or Paste content to validate a draft before you publish it.
2
Enter your URL or file
Type a bare domain, a site root, or a direct /llms.txt URL — the protocol is added for you. In paste mode, drop the full markdown into the text box.
3
Run the check
Press Check or Validate. The file is fetched, split into specification blocks, and scored against the five structural rules.
4
Read the score and grade
The score ring shows weighted compliance out of 100 with a letter grade, plus how many rules passed, warned, or failed.
5
Work through the findings
Each finding names the rule, the line number, and the exact change to make. Expand a rule card to see every detail behind its status.
6
Fix, publish, and re-check
Apply the fixes, upload the file to your site root so it is served at yourdomain.com/llms.txt, then run the URL back through the checker to confirm it passes.

llms.txt Checker

What is llms.txt?

The required order, per the spec

The 5 validation rules we check

Markdown format

H1 project title

Blockquote summary

Detail blocks without headings

H2 sections with file lists

How to write a compliant llms.txt

Implementation guide

The spec template

How to use this checker

Pick an input mode

Enter your URL or file

Run the check

Read the score and grade

Work through the findings

Fix, publish, and re-check

Frequently asked questions about llms.txt

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