What Is Noindex?
A noindex directive instructs search engines not to index a page, so it will not appear in search results. It is typically added as a meta robots tag in the page head, content="noindex", or via an X-Robots-Tag HTTP header for non-HTML files.
Unlike robots.txt, which controls crawling, noindex controls indexing. For the directive to work, search engines must be able to crawl the page to see the tag, so a page should not be blocked in robots.txt and set to noindex at the same time.
When to Use Noindex
Use noindex for pages that should exist for users but not appear in search: thank-you and confirmation pages, internal search results, thin or duplicate pages, staging content, and certain paginated or filtered URLs.
Noindex keeps low-value pages out of the index without removing them from the site, which protects overall site quality signals. Pages you both want hidden and do not need crawled can be handled with noindex while still allowing crawl access so the tag is read.
Common Noindex Mistakes
The most damaging mistake is accidentally applying noindex to important pages, which removes them from search entirely. This can happen through template errors or leftover tags from a staging environment, so audits should always check for unintended noindex directives.
Another mistake is combining noindex with a robots.txt disallow on the same page. If crawlers cannot access the page, they never see the noindex tag, so the URL may still get indexed. Allow crawling on pages you want noindexed so the directive can take effect.