Noindex
Noindex is an instruction that tells search engines not to include a page in their search results. It is set with a robots meta tag in the page's HTML, or with an X-Robots-Tag response :
<meta name="robots" content="noindex">
A noindex page can still be visited normally; it just never appears in search. That makes an accidental noindex easy to miss - the page looks fine, but no one can find it through a search engine. The none directive means the same as noindex, nofollow.
Noindex only works if the crawler can actually reach the page: if also disallows the URL, the crawler never fetches it, never sees the noindex tag, and the page can still be indexed anyway - usually with no snippet, just the bare URL. To reliably keep a page out of search, allow crawling and rely on noindex alone.
Learn more
- Block search indexing with noindex - Google's guidance on noindex