What is a robots.txt file?
A robots.txt file is a small text file placed at the root of a website that gives crawl instructions to bots such as Googlebot. It tells crawlers which parts of the site they can access and which parts they should avoid.
Important detail: robots.txt controls crawling, not guaranteed indexing. A URL can still appear in search results in some situations even if crawling is blocked.
What does a robots.txt tester do?
A robots.txt tester fetches the robots.txt file from the correct URL, shows its contents, and helps identify common issues. That includes things like accessibility problems, missing rules, missing sitemap lines, and directives that may block crawling more broadly than intended.
In short, it helps you quickly validate that the file is reachable and behaving the way you expect.
Robots.txt vs meta robots vs X-Robots-Tag: what’s the difference?
These three controls do different jobs. Robots.txt manages crawler access at the site or path level. Meta robots handles indexing instructions inside HTML pages. X-Robots-Tag sends indexing instructions at the HTTP header level and also works for non-HTML files such as PDFs.
If you want to stop a page from being indexed, robots.txt is usually not the right tool. Meta robots or X-Robots-Tag are the better fit for that job.
Where should robots.txt be located on a website?
Robots.txt must live at the root of the host, for example:
example.com/robots.txt
Not inside folders like /blog/robots.txt or other subpaths. If your site uses subdomains, each subdomain needs its own robots.txt file at that subdomain’s root.
Can I test robots.txt for a subdomain?
Yes. A subdomain is treated as a separate host, so it has its own robots.txt file. That means example.com and blog.example.com do not automatically share the same robots.txt rules.
To test the correct one, run the checker using the exact subdomain you want to inspect.
What happens if my site has no robots.txt file?
Most search engine bots will still crawl the website normally. In practice, no robots.txt usually means there are no special crawl restrictions in place.
The downside is that you lose an easy way to guide crawlers away from low-value sections such as admin areas, cart pages, internal search results, or other technical paths. You also miss the chance to include a sitemap directive there.
How can I check if my robots.txt is valid?
Paste your domain into the tool and run the test. If the robots.txt file is fetched successfully and the rules look structurally correct, that is a strong first sign that the file is valid.
A validator is especially useful for catching syntax issues, missing directives, and accidental crawl blocks before they start affecting SEO.
Why is my robots.txt not working as expected?
Common reasons include placing the file in the wrong location, editing the wrong host version, using rules that are too broad, or dealing with redirects, 403 errors, 404 errors, or other server responses that stop crawlers from reading the file properly.
Sometimes the file itself is fine, but the logic is too aggressive. A single broad disallow rule can block much more than you intended.
What are common robots.txt mistakes that hurt SEO?
The most damaging mistakes include accidentally blocking the entire site, blocking important CSS or JavaScript files, blocking pages you actually want indexed, placing the file outside the root, and using robots.txt when you really needed noindex controls instead.
Another common miss is forgetting to include a sitemap line. That is not always critical, but it is still helpful.
Does this robots.txt tester store the domains I search?
No. The tool does not store a history of the domains you test and does not collect personal data through the checking process itself.
It is built to give you a fast technical check without adding privacy friction.