How to Use an AI Crawler Checker with robots.txt to Control Bot Access

How to Check Which AI Crawlers Your robots.txt Is Actually Blocking

If you run a website and you're not sure whether your robots.txt file is stopping AI bots like GPTBot, ClaudeBot, or CCBot from scraping your content, you're not alone — and the answer matters more than ever. An AI crawler checker lets you test your robots.txt rules against known AI user agents, so you can see exactly what's being allowed or blocked before any damage is done. The short version: paste your robots.txt into a checker tool, select the AI crawler you want to test, and it will tell you if that bot is permitted to access any given URL on your site.

Why AI Crawlers Are Different from Google's Bots

Most site owners are comfortable managing Googlebot or Bingbot. Those bots operate under well-established rules, and blocking them has obvious consequences for search rankings. AI crawlers are different. They're not indexing your site for search results — they're harvesting your content to train large language models or power AI-generated answers.

According to Originality.ai, over 60% of the top 1,000 websites had not blocked any major AI crawler as of early 2024. That's a staggering number when you consider what's at stake. If GPTBot crawls your original research, tutorials, or product copy, that content can end up embedded in an AI model that competes directly with you — without credit, without traffic, and without payment.

Here's where it gets complicated, though. Not all AI crawlers are created equal. Some, like Perplexity's bot, are used to power real-time AI search results that can actually send traffic back to your site. Blocking everything indiscriminately might not be the right call.

My personal take: treat AI crawlers the way you'd treat a vendor asking to use your content. Ask what they're offering in return. If the answer is nothing, block them.

How an AI Crawler Checker Works with robots.txt

A robots.txt file is a plain text file sitting at the root of your domain — yourdomain.com/robots.txt. It tells crawlers which pages they can and can't access. An AI crawler checker tool reads this file and simulates what a specific bot would see when it requests a URL.

Here's a concrete example. Say you've added this to your robots.txt:

` User-agent: GPTBot Disallow: /

User-agent: CCBot Disallow: / `

You'd run that through a checker tool — options include Merkle's robots.txt tester, Google's own Search Console tester (limited to Google bots), or newer dedicated tools like Cloudflare's AI Audit feature — and test a URL like /blog/my-best-guide. The checker will confirm whether GPTBot would be blocked from that path.

This works — but only under the condition that the AI company actually respects robots.txt. OpenAI officially honors robots.txt for GPTBot. Anthropic does for ClaudeBot. Others are less reliable. A checker confirms your syntax is correct, not that every bad actor will comply.

The most common mistake I see people make is writing a Disallow rule with a typo, or placing the robots.txt at the wrong directory level. A checker catches those instantly.

Known AI Crawlers to Include in Your robots.txt

Before you can block or test anything, you need to know the actual user agent strings these bots use. Here's a table of the major ones as of 2024:

Google-Extended is worth calling out separately. It's the user agent Google uses to train Bard/Gemini and power AI Overviews. You can block Google-Extended without affecting your regular Google Search rankings — those are governed by Googlebot, a completely different agent. Per Semrush data, a significant share of site owners didn't know this distinction existed, which means they were either unknowingly feeding Google's AI tools or over-blocking and hurting their SEO.

That's an important distinction. Don't block Googlebot trying to block Google's AI. Use Google-Extended.

Step-by-Step: Testing Your robots.txt Against AI Crawlers

Let me walk through what I'd actually do if I were auditing a site today.

Step 1: Pull up your current robots.txt Go to yourdomain.com/robots.txt in your browser. Copy the whole thing.

Step 2: Choose a checker tool For a quick test, Merkle's robots.txt tester is free and handles custom user agents well. Cloudflare's AI Audit (available in their dashboard if you're on their network) is worth using if you're already a Cloudflare customer — it does ongoing monitoring, not just one-off checks.

Step 3: Enter the AI crawler's user agent Paste the user-agent string exactly as listed by the AI company. Even a capital letter difference can break the match.

Step 4: Test your most valuable URLs Don't just test your homepage. Test your highest-traffic blog posts, your pricing page, your documentation. These are the pages AI companies want most.

Step 5: Fix and re-test If the checker shows a bot can access pages you want protected, edit your robots.txt, re-upload, and run the test again. It's a loop, not a one-time task.

One scenario worth thinking through: imagine you run a recipe site with 3,000 original recipes. You've got GPTBot blocked but forgot to add CCBot. A checker run reveals CCBot has full access. Without that audit, your entire recipe database could be feeding Common Crawl's dataset, which in turn feeds dozens of AI models. That's 3,000 pieces of original content gone sideways — not because your intention was wrong, but because the syntax wasn't right.

FAQ

What is an AI crawler checker?

An AI crawler checker is a tool that tests your robots.txt file against specific AI bot user agents to confirm whether those bots are allowed or blocked from accessing your URLs.

Does blocking AI crawlers in robots.txt actually work?

It works for companies that officially honor robots.txt, like OpenAI and Anthropic. It won't stop bad-faith scrapers who ignore the standard — but it does create a documented record of your intent, which matters legally.

Can I block AI crawlers without hurting my Google rankings?

Yes. Block Google-Extended to stop Google's AI training tools, and leave Googlebot alone. They're separate user agents and affect completely different systems.

How often should I check my robots.txt for AI crawlers?

New AI crawlers are introduced regularly. A quarterly audit is a reasonable baseline — more frequently if you're in a content-heavy niche like publishing, law, or education.

Is there a way to allow some AI crawlers but block others?

Absolutely. You can write individual Disallow rules per user agent. Allow PerplexityBot if you want AI search referral traffic, block GPTBot and CCBot if you don't want your content used for training.

Start With One Audit Today

The technology around AI crawling is moving fast, and the robots.txt standard is still the most accessible tool most site owners have to respond to it. Run your robots.txt through an AI crawler checker, compare it against the full list of known AI user agents, and close any gaps you find. That single step, done today, protects everything you publish tomorrow.