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To help your WordPress installation be more optimized for search engines, this plugin will include a ‘noindex’ meta tag in the header of any duplicate posts. 
Robots will not index any posts with matching title tags, which is a known indicator of negative SEO. This is very useful for automated posting and working with a large amount of posts.

Noindex Duplicate Posts

This plugin will automatically add a 'Noindex' meta tag to posts that are a duplicate determined by the slug and preexisting post names.

This plugin can add rel=”noindex,nofollow” to archive, tag, and category links. You can configure exactly which links are given which attributes. For instance, you could add rel=”noindex,nofollow” to all of your tag links, rel=”noindex” to all of your archive links, and nothing to your category links.

Noindex/Nofollow links

This plugin can add rel="noindex,nofollow" to archive, tag, and category links. You can configure exactly which links are given which attrib …

Noindex Duplicate Posts vs Noindex/Nofollow links