Prevent Robot Indexing with Response Headers

Every so often you have parts of your website that would be better off not indexed by search engines.  API calls, search result pages, PDF documents -- all examples of responses which may not have value outside of the current user.  No we all know we can signal to the search engines not to index pages using a META tag, but oftentimes service calls and documents don't get the luxury of a META tag.  Luckily you can add a header to prevent these responses from being indexed.

The header name is X-Robots-Tag should be easy to add using the server-side language you prefer.  For example, adding this header with PHP may look like:

header('X-Robots-Tag: noindex');

If you're using a Django-based python site, the could would look like:

response['X-Robots-Tag'] = 'noindex'

This header can also be set within your .htaccess or httpd configuration files:

<Files ~ "\.pdf$">
  Header set X-Robots-Tag "noindex"
</Files>

The truth is that there's no guarantee that something your server serves wont be indexed by a search engine, but small tweaks like this can ensure your search engine standing can improve and that users don't find their way to "dead" parts of your site via search engines.