Noindex is a directive that can be used in the HTML code of a webpage or in HTTP headers to instruct search engines not to index a particular page. When a search engine’s crawler, such as Googlebot, encounters the noindex directive, it will recognize that the content on that page should not be included in the search engine’s index. As a result, the page will not appear in search engine results pages (SERPs). The noindex directive is useful for webmasters who want to prevent certain pages from being publicly searchable, such as private pages, duplicate content, or pages with sensitive information. It’s important to note that while noindex tells search engines not to index a page, it does not prevent the crawler from following links on that page unless a nofollow directive is also used.