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HTTP Headers - Functional specification

Yoast SEO constructs and optimizes various HTTP headers, in order to manage indexing, assist with debugging, and compliment other functionality.


It's sometimes desirable to prevent 'non-page' resources (resources like PDFs or XML files, which don't support HTML <head> mark-up) from being crawled or indexed by search engines. When the content management system serves these resources, we can manipulate their HTTP headers to provide crawl and indexing directives via an x-robots-tag HTTP header.

We do this in the following cases:

  • All XML sitemaps return a noindex, follow directive. NB, this does not affect sitemap consumption or processing.
  • XMLRPC files return a noindex, follow directive.


When our redirect manager executes a redirect, we pass a value of 'Yoast SEO Premium' to WordPress' wp_redirect() function. This adds a x-redirected-by header to the response, which can be helpful when debugging.