What does the llms.txt validator check?

It applies an editorial checklist to the proposed Markdown format: site heading, summary, organized links, size and response content type. Docs headings, absolute links and summary-length limits are tool recommendations, not universal crawler requirements. Passing cannot prove engine adoption.

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.

Does this guarantee an AI citation?

No. A crawlable, accurate page can still be omitted. Retrieval, source selection and generated answers vary between products and requests; these checks improve the evidence available, not guarantee placement.

How do I tell whether an improvement worked?

Compare like-for-like checks and retain the underlying evidence. Track correct brand mentions, source-linked citations and qualified referral visits separately. Do not call a technical score a traffic forecast or attribute every change to one edit.

Where are crawl restrictions configured?

Use robots.txt for preferences addressed to compliant crawlers, and authentication for private content. llms.txt does not enforce either crawl restrictions or a right to use content.

llms.txt Validator

Review Markdown structure, summary and links against a practical publishing checklist—not a universal AI indexing standard.

Quick answer

This validator checks live or pasted llms.txt formatting, links and response details against its own publishing checks. A Docs heading, absolute HTTPS links and summary limits are editorial checks, not universal AI crawler requirements. A passing result does not prove an engine consumed the file.

Live URL

Fetch a live llms.txt URL or paste contents below.

Or paste file contents

Validation results

0 passed0 warnings1 errors

File is empty.
Fix: Add at least an H1 site name and a summary.

Cleaned version

// Add an H1 site name before publishing

Why validation matters

llms.txt is a proposed Markdown guide to your site's public content. Validation helps find formatting and maintenance issues, but does not show whether a particular AI engine reads the file. This tool's size, section-name and summary limits are editorial recommendations rather than universal requirements.

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

A missing heading or unclear summary makes the site harder to understand.
Absolute HTTPS links simplify checking; relative links are not inherently invalid.
Use descriptive section headings; a literal ## Docs heading is not mandatory.
Keep the guide concise; the tool's size warning is not a published crawler limit.
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 check the public response. A successful fetch does not prove that ChatGPT, Claude or Perplexity consumed it or will cite it.

Using llms.txt Validator

What llms.txt does—and does not do

llms.txt is a proposed Markdown convention for presenting a concise site overview and curated links. It is not a robots policy, licensing agreement, authentication control or universal AI indexing requirement. An H1 site name, a useful summary and organized Markdown links help readers understand the site. The proposal does not mandate a section literally called Docs or a universal 150-character summary. Adoption differs by consumer; do not claim that every major AI crawler reads it.

Deploy at the public root without changing the site

Serve the file at /llms.txt with a successful response containing the intended text, not a themed HTML error page or sign-in screen. Use your CMS’s supported public-file feature, a static hosting asset or an explicitly configured text response. If the platform reserves root paths, confirm an officially supported deployment method before adding a plugin or proxy. Check the custom domain as well as the hosting preview, because redirects and caches can behave differently.

Choose a small set of useful destination pages

Link stable canonical pages: product overview, pricing, documentation, support policies and important guides. Use descriptive link labels and optional concise context so a reader knows what each page covers. Absolute HTTPS links are a practical publishing choice, not evidence that relative links automatically trigger HTTP errors. Exclude private dashboards, draft pages, tracking URLs and obsolete content. Keep linked information and translations current; do not list a page merely to inflate the file.

Verify after publishing and after important changes

Fetch the deployed file and inspect the response body, status and content type; text/plain with a UTF-8 charset is a sensible default. Follow the destination links to confirm they are public and relevant. Compare the live file with the version you intended to deploy after cache invalidation. A validator can identify formatting and link problems, but it cannot prove that an engine read the file or that a future answer will cite your site.

Interpret warnings without confusing them with the specification

A local validator may recommend absolute URLs, a named documentation section or a short summary as editorial checks. Those recommendations are not universal requirements of the llms.txt proposal. Check the actual Markdown and linked pages, and keep access preferences in robots.txt. A pass means the checks performed found no listed issue; it does not certify vendor adoption, link reachability unless tested, licensing compliance or eventual AI visibility.

Evidence and next actions

Check	Evidence to retain	Action
File response	Successful /llms.txt response and readable Markdown	Fix HTML fallbacks and private routes
Site identity	A clear H1 and concise factual overview	Remove promotional or contradictory claims
Content links	Current canonical pages with useful labels	Replace obsolete or redirected links
Access policy	Separate robots.txt and authentication settings	Do not put Allow/Disallow rules in llms.txt
Maintenance	Published version and destination-page changes	Refresh when products or URLs change

Implementation checklist

Confirm your CMS supports the chosen public root-path method.
Use Markdown, not a copied robots.txt template.
Describe what the site actually offers.
Include stable public URLs and clear labels.
Test the real domain after deployment.
Treat the file as optional context, not a citation guarantee.

Validate an llms.txt draft before publishing

1
Establish a baseline
Save the page URL, date, language, target market and exact questions before editing. Record what the page actually says and what each tested answer cites; a mention without a source link is not a citation.
2
Make one coherent change
Resolve the clearest failure first, then check the published page rather than only an editor preview. Keep an implementation log so unrelated redesigns, campaigns or product changes are not mistaken for the effect of this work.
3
Repeat and compare
Repeat the same questions and technical checks after deployment. Keep engines and measurement conditions consistent, report sample size, and inspect answer accuracy alongside citations. A single response is not a stable ranking.

Want the full picture?

OptimAIze checks structured data, content, crawler access and answer-readiness to help you investigate concrete issues. Technical improvements do not guarantee AI citations.

Run a full GEO + AEO scan on your site

Frequently asked questions

What does the llms.txt validator check?: It applies an editorial checklist to the proposed Markdown format: site heading, summary, organized links, size and response content type. Docs headings, absolute links and summary-length limits are tool recommendations, not universal crawler requirements. Passing cannot prove engine adoption.
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.

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