llms.txt validator

What this tool checks

llms.txt is a plain-Markdown file at your site root (/llms.txt) that gives AI crawlers a curated map of your most important pages, and this check confirms it both exists and follows the llmstxt.org format — an H1 title, a summary, section headings, and link lists. A missing or malformed file means any AI crawler that looks for an llms.txt index finds nothing and has only your raw HTML to infer site structure from, so a clean, valid llms.txt makes your key content easier to find, read, and cite.

What it looks at

File exists at root

The validator requests /llms.txt at your domain root and confirms it returns HTTP 200 as plain text/Markdown — AI crawlers only look there, so a file buried in a subfolder is invisible.

H1 title line

The spec requires the first line to be a single H1 (# Site name) naming the project — it's the anchor an engine reads to identify whose content this is.

Blockquote summary

A short `>` summary directly under the title tells the model what the site is about in one sentence, priming it to summarize and cite you accurately.

H2 section headings

Content is grouped under `##` sections (Docs, Guides, API), giving the file a scannable structure the crawler can navigate by topic.

Link lists

Each section lists `- [title](url): description` entries pointing to your key pages; well-formed links are what actually route the AI to citable source material.

File size / conciseness

llms.txt is meant to be a lean index, not a dump — an oversized file risks truncation or being ignored, so the check flags files that blow past a sensible size.

How to use it

1. Paste your site URL (or the direct /llms.txt link) and run the check.
2. Review the flagged items — missing file, absent title or summary, sections with no links, or an oversized file.
3. Fix the gaps in your llms.txt (or regenerate it with the paired generator) and re-run until it validates clean.

Frequently asked questions