Robots.txt Checker & Validator
Paste your robots.txt and instantly audit AI crawler access, detect syntax errors, and get copy-paste fixes.
What Does a Robots.txt Checker Do?
A robots.txt checker (also called a robots.txt validator or tester) analyzes your website's robots.txt file to find configuration issues that could be blocking search engines and AI crawlers from accessing your content. It validates the syntax, checks for conflicting rules, and tells you exactly which bots are allowed or blocked.
In 2026, this is more important than ever. Your robots.txt is not just a search engine gatekeeper. It now controls whether AI platforms like ChatGPT, Claude, Perplexity, and Google AI Overviews can read and cite your content. Our research shows that over 40% of B2B websites unintentionally block at least one critical AI crawler.
This free checker audits your robots.txt against 16 crawlers spanning AI, search, and social platforms. It detects syntax errors, identifies blocking issues, and generates copy-paste fixes. Whether you are debugging AI search visibility issues or running a technical SEO audit, start here.
How to Use This Robots.txt Checker
- Find your robots.txt at
yourdomain.com/robots.txtand copy the full content. - Paste it into the text area above.
- Click "Run Audit" to scan for issues across 16 AI, search, and social crawlers.
- Review the score, syntax errors, and per-crawler status cards.
- Use the recommended fix snippets to update your file.
Robots.txt Best Practices for AI Search Visibility
What we recommend based on auditing hundreds of B2B sites.
List AI crawlers explicitly. Do not rely on wildcards.
A User-agent: * Allow: / rule technically permits all bots. But if you ever add a Disallow rule to that block, every AI crawler inherits it. The only safe approach is to give each critical AI bot its own User-agent block with an explicit Allow: /. This protects you from accidental blocking when someone on your team adds a staging path restriction six months from now.
Place specific bot rules before the wildcard block.
Most crawlers follow the most specific matching rule. But some older parsers read top-to-bottom and apply the first match. Either way, putting your GPTBot, ClaudeBot, and PerplexityBot blocks above User-agent: * eliminates ambiguity. It costs nothing and prevents a category of bugs that are painful to debug.
Always include a Sitemap directive.
A Sitemap line at the bottom of your robots.txt is the fastest way to tell every crawler where your XML sitemap lives. It is trivial to add and disproportionately helpful for new sites, large sites, and sites with deep content that might not be discovered through internal linking alone.
Audit after every CMS update, CDN change, or migration.
We have seen major SaaS companies lose AI visibility for weeks because a platform update silently overwrote their robots.txt. WordPress plugin updates, Vercel rewrites, Cloudflare settings. Any of these can inject a Disallow: / that wipes out months of work. Make robots.txt validation a step in your deployment checklist.
Do not block CSS and JavaScript files.
Google needs to render your pages to evaluate content quality and Core Web Vitals. Blocking CSS/JS files via robots.txt forces Googlebot to index a stripped-down HTML version of your site, which almost always hurts rankings. This applies to AI crawlers too. If they cannot render your page, they cannot understand your content structure.
Keep the file small and readable.
Crawlers have a size limit for robots.txt (Google caps at 500KB). More importantly, a complex robots.txt is harder to maintain and more likely to contain conflicting rules. If your file is longer than 50 lines, something is probably wrong. Simplify.
Common Robots.txt Mistakes We See Every Week
Real scenarios from real audits. Tap any card to see the fix.
The "I blocked everything by accident" mistake
User-agent: * Disallow: /
This blocks every crawler from every page. Google cannot index you. ChatGPT cannot cite you. Your site is invisible.
Blocking GPTBot while expecting ChatGPT citations
User-agent: GPTBot Disallow: /
Some CMS security plugins add this by default. It completely removes your site from ChatGPT's knowledge and browsing.
Forgetting Google-Extended exists
User-agent: Googlebot Allow: / # No Google-Extended rules
Allowing Googlebot gives you search visibility. But Google-Extended controls AI training and Gemini. Without it, you are not in AI Overviews.
The staging robots.txt that went to production
# DO NOT DEPLOY TO PRODUCTION User-agent: * Disallow: /
Happens more than you would think. A staging environment blocks all bots by design. Someone copies the file during deployment. Traffic drops. Nobody connects the dots for weeks.
No Sitemap directive anywhere
User-agent: * Allow: /
The file works, but you are leaving discoverability on the table. Crawlers have to rely entirely on internal links to find your content.
Misspelling the directive name
Useragent: * Dissallow: /admin/
"Useragent" and "Dissallow" are not valid directives. Crawlers silently ignore them. Your rules do nothing. The syntax checker above will catch these.
Frequently Asked Questions
Robots.txt Is Just the Start
Fixing your robots.txt unblocks crawlers. But becoming the recommended answer in ChatGPT, Perplexity, and AI Overviews takes a full AI visibility strategy.
Get a Free AI Visibility Audit →