Robots.txt vs LLMS.txt vs Cats.txt, Key Differences, Purposes for AI SEO

In an era where AI-powered search and content generation are rapidly evolving, site owners must understand how different “.txt” files influence crawling, indexing, and content consumption by large language models (LLMs). In particular, robots.txt, llms.txt, and the hypothetical cats.txt each have distinct purposes. In this blog, we’ll compare these three, explain when and how to use them, and show how they can jointly support your AI SEO strategy. 

What Is robots.txt?

robots.txt is a plain text file at the root of your website (for example, example.com/robots.txt) that tells automated crawlers which URLs they may or may not request. It follows the Robots Exclusion Protocol, used since 1994 and formalized as an internet standard (RFC 9309) in 2022.

Basic syntax:

User-agent: *

Disallow: /admin/

Allow: /admin/help/

Sitemap: https://example.com/sitemap.xml

• User-agent: which crawler the rules apply to (* means all)
• Disallow / Allow: paths the crawler should not or may request
• Sitemap: where to find your XML sitemap

robots.txt and AI crawlers

Most major AI companies publish crawler names and say they respect robots.txt. Many separate bots that collect training data from bots that fetch pages to answer users in real time, so you can make different choices for each.

(Crawler names and purposes change. Check each company's current documentation before editing your file.)

What robots.txt can and can't do

• It can stop compliant crawlers from requesting pages, manage crawl load and let you allow search bots while blocking training bots.
• It can't enforce anything. Badly behaved bots can ignore it.
• It can't reliably keep a page out of search results. A blocked URL can still be indexed (without its content) if other pages link to it. Use a noindex meta tag (and let crawlers see it) or password protection instead.
• Blocking Googlebot to avoid AI Overviews also removes you from Google Search. There is no separate Googlebot just for AI Overviews.

Newer AI preference signals in robots.txt

Two efforts let sites express how content may be used by AI, beyond simple allow and block rules: Cloudflare's Content-Signal directive (for example, search=yes, ai-input=yes, ai-train=no) and the IETF AI Preferences (AIPREF) Content-Usage proposal. Both are still emerging and not universally honored, so treat them as statements of preference, not guaranteed controls.

What Is llms.txt?

llms.txt is a proposed file format, introduced in 2024 by Jeremy Howard of Answer.AI, that gives large language models a short, curated guide to a website's most useful content. It sits at the root of a site (example.com/llms.txt) and is written in Markdown, so it is easy for both people and AI tools to read.

Unlike robots.txt, llms.txt does not allow or block anything. It is closer to a curated reading list or table of contents for AI.

Example llms.txt:

# Example Company

> Example Company provides SEO and AI search services for businesses in India and worldwide.

## Services

- [SEO Services](https://example.com/seo/): Technical, on-page and content SEO

- [GEO Services](https://example.com/geo/): Visibility in AI answers

## Guides

- [robots.txt vs llms.txt](https://example.com/blog/robots-vs-llms/): How the two files differ

## Optional

- [About Us](https://example.com/about/)

The proposed structure is an H1 with the site or project name, a short blockquote summary, then sections of links with brief descriptions. Some sites also publish an llms-full.txt containing full page text in Markdown.

Does llms.txt help AI SEO?

The honest answer in 2026: there is little public evidence that it does, for search-style AI visibility.

• Google has said publicly that it does not use llms.txt for Search, and AI Overviews rely on Google's normal crawling and index.
• Major AI assistants have not confirmed that they use llms.txt to choose which sites to cite or recommend.
• Where llms.txt is clearly useful is in developer documentation: coding assistants and AI tools can load a clean, Markdown version of docs, and many software companies publish one for that reason.

When llms.txt is worth adding

• You have technical documentation, an API or a knowledge base that developers or AI agents use.
• You want a clear, low-maintenance summary of your key pages, which is also a useful internal exercise.
• It costs very little to create and keep updated.

Just don't expect it to replace robots.txt, structured data, good content or genuine authority, and don't promise clients that it will improve rankings or AI citations.

What Is cats.txt?

cats.txt is a deliberately satirical "web standard" created by technical SEO Mark Williams-Cook and reported by Search Engine Journal in August 2026. The file formally declares a site's office cats: their names, job titles, breeds and an affection score. It was published with a serious-looking specification, on purpose, to test the evidence people use to claim that llms.txt works.

What happened:

• AI and search crawlers, including GPTBot, ClaudeBot, PerplexityBot and Googlebot, requested the cats.txt file, as they request almost any file on a website.
• Google indexed it.
• ChatGPT, when asked, explained at length how cats.txt could help a site rank.
• Some SEOs started adding cats.txt to their own sites.

Those are the same kinds of "proof" often shared for llms.txt. Because cats.txt is made up and cannot possibly improve anything, the experiment shows that these observations don't prove a file has any effect.

The lesson for AI SEO

Better evidence to look for: official documentation from the AI or search company saying it uses the file, and measurable changes in citations, rankings or traffic compared with a control.

Should you add cats.txt? No. It has no function. If you liked the idea, the real takeaway is to test claims about new AI SEO files before adopting them.

(Note: earlier versions of this article described cats.txt as a hypothetical file for content categories. That use was our own illustration, not a real standard.)

4. robots.txt vs llms.txt vs cats.txt: Key Differences

In one line each: robots.txt controls access, llms.txt suggests content, and cats.txt tests whether we can tell the difference between a real signal and a file that merely gets crawled.

5. What to Put on Your Site: A Practical Setup for AI SEO

Step 1: Decide your AI policy in robots.txt

Choose whether you want to appear in AI answers, be used for AI training, or both. Most businesses want to be visible and cited in AI search, so they allow search-style AI crawlers. Some also choose to block training-only crawlers.

Example: visible in search and AI answers, opting out of some training:

# Search engines (including Google AI Overviews and Bing Copilot)

User-agent: Googlebot

Allow: /

User-agent: Bingbot

Allow: /

# AI search and user-requested fetches

User-agent: OAI-SearchBot

Allow: /

User-agent: ChatGPT-User

Allow: /

User-agent: PerplexityBot

Allow: /

User-agent: Claude-SearchBot

Allow: /

# Training-focused crawlers (optional: block if you don't want training use)

User-agent: GPTBot

Disallow: /

User-agent: Google-Extended

Disallow: /

User-agent: CCBot

Disallow: /

# Everyone else

User-agent: *

Disallow: /wp-admin/

Allow: /wp-admin/admin-ajax.php

Sitemap: https://example.com/sitemap.xml

Blocking training crawlers is a business choice, not an SEO requirement. If you want maximum AI visibility, you may choose to allow them too. Also note that blocking Google-Extended affects Gemini but not Google Search or AI Overviews.

Step 2: Check your CDN and firewall

Cloudflare and other services can block AI bots at the network level, regardless of robots.txt. Make sure your bot settings match the policy you chose.

Step 3: Add llms.txt if it makes sense for you

Create a short llms.txt listing your key service pages, guides and documentation, each with a one-line description. Keep it updated when important pages change, and never list private or blocked pages.

Step 4: Focus on what actually earns AI citations

• Clear, answer-first content with definitions, comparisons and FAQs
• Pages that load fast and render without heavy JavaScript
• Structured data such as Organization, Article, FAQ and Product
• Consistent brand facts across your site, profiles and directories
• Genuine mentions on trusted third-party sites

Step 5: Measure, don't assume

Use Search Console's Generative AI report (beta), Bing Webmaster Tools' AI Performance report for Copilot citations, server logs and GA4 AI-referral tracking to see what actually changes. Our AI SEO services and sister brand GEO Digital Agency can help set this up.

Conclusion

robots.txt, llms.txt and cats.txt are three very different things. robots.txt is the essential, widely supported way to control crawler access, including for AI. llms.txt is an optional, low-cost guide whose impact on AI visibility is still unproven. cats.txt is a useful reminder that a file being crawled, indexed or praised by a chatbot is not proof that it works.

For real AI SEO results, get your robots.txt policy right, make your best content easy to crawl and understand, build genuine authority and measure what changes. If you'd like help, our team can audit your robots.txt, AI crawler access and AI visibility.