Why Your Robots.txt File Matters More Than Ever (SEO + AI Visibility) | Corco Labs

Your robots.txt file is one of the oldest standards on the web—and one of the most overlooked. It’s a plain text file that tells crawlers what they can and can’t access. Simple in theory, consequential in practice.

With AI systems now crawling the web for training data and real-time answers, robots.txt has become a policy decision, not just a technical one. Block the wrong bot and your content disappears from AI-generated answers. Leave it wide open and you might be training someone else’s model for free.

What robots.txt Actually Does

The robots.txt file lives at the root of your domain (yourdomain.com/robots.txt) and follows the Robots Exclusion Protocol. When a well-behaved crawler visits your site, it checks this file first and respects the rules you’ve set.

A basic robots.txt looks like this:

User-agent: *
Allow: /

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

This says: “All bots can access everything, and here’s where to find the sitemap.”

A more restrictive version:

User-agent: *
Disallow: /admin/
Disallow: /api/
Disallow: /private/

User-agent: GPTBot
Disallow: /

User-agent: ClaudeBot
Disallow: /

This blocks admin and API paths from all crawlers, and completely blocks OpenAI’s and Anthropic’s bots from crawling anything.

Why This Matters for SEO

Search engines like Google rely on crawling to index your content. If your robots.txt blocks Googlebot—or blocks important pages by accident—those pages won’t appear in search results.

Common SEO mistakes with robots.txt:

Blocking CSS/JS files: Modern search engines need to render your page. Blocking assets can hurt rankings.
Blocking entire sections unintentionally: A misplaced Disallow: / can block your whole site.
Forgetting to update after a redesign: Old rules can block new URL structures.
No sitemap reference: Missing the Sitemap: directive means crawlers have to guess which pages exist.

The good news: these are easy to fix once you know they’re there. The bad news: many sites don’t check.

Why This Matters for AI Visibility

AI systems like ChatGPT, Claude, Perplexity, and Google’s AI Overviews pull content from the web to answer questions. If your robots.txt blocks their crawlers, your content won’t be included.

This creates a tradeoff:

Allow AI crawlers: Your content can appear in AI-generated answers, potentially driving traffic and building authority.
Block AI crawlers: Your content won’t be used to train models or appear in AI responses, but you lose visibility in an increasingly AI-first search landscape.

There’s no universally right answer. A news site might want AI attribution and traffic. A creative studio might not want their work used for training without compensation. The point is to make the decision deliberately.

Common AI Crawlers You Should Know

Here are the major AI-related user agents and what they’re used for:

User-Agent	Company	Purpose
GPTBot	OpenAI	Training and browsing for ChatGPT
ChatGPT-User	OpenAI	Real-time browsing in ChatGPT
ClaudeBot	Anthropic	Training and research
Claude-Web	Anthropic	Real-time browsing in Claude
Google-Extended	Google	AI training (Bard/Gemini)
PerplexityBot	Perplexity	Real-time search answers
CCBot	Common Crawl	Open dataset used by many AI systems
Bytespider	ByteDance	Training for TikTok’s AI features

Blocking GPTBot won’t affect your Google rankings, but it will affect whether your content appears in ChatGPT’s answers.

The llms.txt Standard

A newer standard called llms.txt is emerging alongside robots.txt. While robots.txt tells bots where they can go, llms.txt tells AI systems how to use your content—attribution preferences, licensing, and which sections are most relevant.

It’s not widely adopted yet, but it’s worth watching. Some sites are already using it to provide structured context for AI systems.

How to Check Your Current Setup

Before making changes, you should know what your robots.txt currently says and whether it’s working as intended.

Here’s what to verify:

Does your robots.txt exist? Visit yourdomain.com/robots.txt directly.
Is it syntactically correct? Typos and formatting errors can break parsing.
Are you blocking important pages by accident? Check the Disallow rules against your actual URL structure.
Is your sitemap referenced? Crawlers should be able to find it.
Are you blocking or allowing AI crawlers intentionally? Check for rules targeting GPTBot, ClaudeBot, etc.

Doing this manually is tedious, especially if you’re checking for AI crawler rules across multiple bots.

We built a Robots.txt Checker that does this automatically. Enter your URL and it will:

Fetch and parse your robots.txt
Check accessibility for major search engines (Googlebot, Bingbot)
Check accessibility for AI crawlers (GPTBot, ClaudeBot, PerplexityBot, and more)
Verify your sitemap is present and reachable
Check for llms.txt support

It’s free, no signup required, and shows you exactly what each bot can and can’t access.

Creating or Updating Your Robots.txt

If you need to create a new robots.txt or update an existing one, the syntax is straightforward but easy to get wrong.

Rather than writing it by hand and hoping for the best, you can use our Robots.txt Generator. It gives you:

Presets for common scenarios (allow all, block AI bots, block everything)
A visual builder for adding custom rules
One-click blocking for known AI crawlers
Sitemap reference handling
Valid, properly formatted output you can copy directly

It’s particularly useful if you want to block AI crawlers but aren’t sure which user agents to target.

Practical Recommendations

Here’s what we suggest for most sites:

Check your current robots.txt using a tool or manual review. Know what you’re starting with.
Ensure Googlebot and Bingbot can access your important pages. If you’re blocking them, it’s probably an accident.
Make a deliberate decision about AI crawlers. Don’t leave it to default—either allow them or block them based on your goals.
Include a sitemap reference. It helps all crawlers discover your pages.
Review after redesigns and migrations. URL structures change; robots.txt rules often don’t get updated.
Test before deploying. A bad robots.txt can tank your traffic overnight.

What’s Next

As AI-powered search becomes more common, robots.txt is evolving from an SEO concern to a content policy decision. The bots are getting smarter, but they still follow the rules—if you set them.

If you haven’t looked at your robots.txt recently, now is a good time. And if you want to check multiple sites or run regular audits, our Robots.txt Checker and Generator are free to use.

Have questions about robots.txt, AI crawlers, or SEO visibility? Get in touch—we’re happy to help.