What does the llms.txt validator check?

It checks the structure AI models expect: an H1 site name, a short blockquote summary, a ## Docs section with absolute https links, optional ## Optional links, reasonable file size, and plain text/markdown content type.

Can I validate a live URL?

Yes. Paste the URL (e.g., https://yourdomain.com/llms.txt) and the tool will fetch it server-side, then run the same checklist. You can also paste the file contents directly.

Is my file content stored?

No. The validator reads the file to run the checks and does not persist it. URLs are fetched once and the response is discarded.

What content type should llms.txt return?

text/plain or text/markdown is best. Avoid serving it as text/html, because that forces crawlers to strip tags before parsing the markdown.

Free llms.txt Validator

Why validation matters

A well-formed llms.txt is the fastest way to tell ChatGPT, Claude, and Perplexity which pages on your site matter most. But a missing H1, a relative link, or a 200 KB file makes the brief unusable. This validator catches the mechanical mistakes before you publish.

What a good file looks like

# Acme Analytics
> Acme Analytics is a privacy-first product analytics tool for B2B SaaS teams.

## Docs
- [Documentation](https://acme.com/docs): Setup, SDKs and data model
- [API Reference](https://acme.com/api): REST endpoints and webhooks
- [Pricing](https://acme.com/pricing): Plans, limits and billing FAQ

## Optional
- [Blog](https://acme.com/blog): Product analytics and privacy engineering
- [Changelog](https://acme.com/changelog): Shipped features by date

Common failures

Missing H1 or summary — the crawler has no context for the rest of the file.
Relative links — crawlers resolve them against the wrong base or fail.
No ## Docs section — the file has no prioritized list of canonical pages.
Too large — llms.txt is a brief, not a sitemap. Keep it under 100 KB.
HTML content type — serve it as plain text or markdown.

After validating

Publish the file at /llms.txt on your domain, then run a full OptimAIze scan to confirm AI crawlers can fetch and parse it the way ChatGPT, Claude, and Perplexity do.

Want the full picture?

This tool generates one piece. OptimAIze scans your whole site, audits structured data, content, crawler access, and answer-readiness — then gives you everything you need to be cited by AI.

Run a full GEO + AEO scan on your site

Frequently asked questions

What does the llms.txt validator check?: It checks the structure AI models expect: an H1 site name, a short blockquote summary, a ## Docs section with absolute https links, optional ## Optional links, reasonable file size, and plain text/markdown content type.
Can I validate a live URL?: Yes. Paste the URL (e.g., https://yourdomain.com/llms.txt) and the tool will fetch it server-side, then run the same checklist. You can also paste the file contents directly.
Is my file content stored?: No. The validator reads the file to run the checks and does not persist it. URLs are fetched once and the response is discarded.
What content type should llms.txt return?: text/plain or text/markdown is best. Avoid serving it as text/html, because that forces crawlers to strip tags before parsing the markdown.