llms.txt validator
Fetch your site's /llms.txt and check it against the llmstxt.org spec. Live, right here.
What this checks
llms.txt is a Markdown file at your domain root that hands AI agents a clean map of your best content. The llmstxt.org spec wants a single H1 title, an optional summary blockquote, and H2 sections of Markdown links. This validator fetches your file and checks each of those, plus whether it's real Markdown and not an HTML error page.
It's a static check, so nothing is stored. Fix the warnings, redeploy, and run it again.
What each result means
| Check | What it means | In a squirrelscan audit |
|---|---|---|
| Not empty | The file has content. An empty file fails and no other check runs. | Reported as a missing H1 and no links. |
| Markdown, not HTML | The body is Markdown. It fails when the server answers with an HTML page, usually a single-page app returning index.html for every path. | Fails a body that starts with `<!doctype html` or `<html` as an SPA fallback. This page also catches bodies that start with other tags, such as `<body` or `<div`. |
| H1 title | The first non-empty line is an H1 such as # Your site name. It fails when there is no H1 or something sits above it, and warns when there is more than one. | Same first-line check. The audit does not count extra H1s. |
| Summary | A > one-line summary blockquote follows the title. The spec makes it optional, so a missing one is a warning. | Not checked. |
| Sections | At least one ## Section heading groups the links. A file with none gets a warning. | Not checked. |
| Links | The file has at least one Markdown link, [name](url). None at all is a warning. | Same check, reported as a recommendation. |
| Link URLs | Every link URL parses. It warns on a URL that does not, and on relative links, since an agent reading the file alone can't always resolve them. | Flags URLs that do not parse. Relative links are not flagged. |
This page checks one file, /llms.txt at the root of the domain you enter. When the root has none, a squirrelscan audit also looks for /.well-known/llms.txt and /docs/llms.txt, and it notes whether /llms-full.txt exists. If a site refuses the request with a 401, 403 or 429, both report the file as not checked rather than missing. The ax/llms-txt rule docs list every message the audit can report.
A minimal valid llms.txt
This file passes every check above. Swap in your own name, summary and links, then serve it at /llms.txt with a text/plain or text/markdown content type.
# Example Co
> Example Co makes invoicing software for small teams.
## Docs
- [Quickstart](https://example.com/docs/quickstart): set up your first invoice
- [API reference](https://example.com/docs/api): every endpoint, with examples
## Optional
- [Changelog](https://example.com/changelog): what changed in each release
Frequently asked questions
- What is llms.txt?
- llms.txt is a Markdown file at your domain root (yoursite.com/llms.txt) that gives AI agents and answer engines a curated, machine-readable map of your most useful content. It's an emerging standard defined at llmstxt.org.
- Where does llms.txt go and what should it contain?
- It lives at the root of your domain, at /llms.txt. The spec wants a single H1 title, an optional summary blockquote, and H2 sections containing Markdown link lists that point at your key pages.
- Does llms.txt help SEO?
- It doesn't change traditional search rankings. It's about agent experience: making it easier for AI crawlers and answer engines to find and cite your best content. It's one of 300+ checks a squirrelscan audit runs.
- Is it free?
- The llms.txt validator, the AI crawler checker, the robots.txt generator and the instant security headers check are free and need no account. The other checks run inside a squirrelscan audit. The squirrel CLI runs audits on your machine for free when you are signed out or pass --offline, with no cap on how many. Signed in, CLI and cloud audits spend credits: every account gets 500 free credits a month. An audit costs 50 credits plus 2 per audited page, and 1 per external link the cloud verifies when link checks are on.
llms.txt is one of 300+ checks
squirrel audit checks llms.txt alongside SEO, performance, security, and agent experience across your whole site. Install the CLI and run it locally, free while signed out.