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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.

Javier Casares

Allows to add a meta-tag for robots noindex in some parts of your WordPress site.
Main pages
<ul>
<li>Front Page: Block the indexing of the site’s front page.</li>
<li>Home: Block the indexing of the site’s home page.</li>
</ul>
Pages and Posts
<ul>
<li>Page: Block the indexing of the site’s pages.</li>
<li>Privacy Policy: Block the indexing of the site’s privacy policy page.</li>
<li>Single: Block the indexing of a post on the site.</li>
<li>Singular: Block the indexing of a post or a page of the site.</li>
</ul>
Taxonomies
<ul>
<li>Category: Block the indexing of the site categories. The lists where the posts appear.</li>
<li>Tag: Block the indexing of the site’s tags. The lists where the posts appear.</li>
</ul>
Dates
<ul>
<li>Date: Block the indexing when any date-based archive page (i.e. a monthly, yearly, daily or time-based archive) of the site. The lists where the posts appear.</li>
<li>Day: Block the indexing when a daily archive of the site. The lists where the posts appear.</li>
<li>Month: Block the indexing when a monthly archive of the site. The lists where the posts appear.</li>
<li>Time: Block the indexing when an hourly, “minutely”, or “secondly” archive of the site. The lists where the posts appear.</li>
<li>Year: Block the indexing when a yearly archive of the site. The lists where the posts appear.</li>
</ul>
Archives
<ul>
<li>Archive: Block the indexing of any type of Archive page. Category, Tag, Author and Date based pages are all types of Archives. The lists where the posts appear.</li>
<li>Author: Block the indexing of the author’s page, where the author’s publications appear.</li>
<li>Post Type Archive: Block the indexing of any post type page.</li>
</ul>
Pagination
<ul>
<li>Pagination: Block the indexing of the pagination, i.e. all pages other than the main page of an archive.</li>
</ul>
Search
<ul>
<li>Search: Block the indexing of the internal search result pages.</li>
</ul>
Attachments
<ul>
<li>Attachment: Block the indexing of an attachment document to a post or page. An attachment is an image or other file uploaded through the post editor’s upload utility. Attachments can be displayed on their own “page” or template. This will not cause the indexing of the image or file to be blocked.</li>
</ul>
Previews
<ul>
<li>Customize Preview: Block the indexing when a content is being displayed in customize mode.</li>
<li>Preview: Block the indexing when a single post is being displayed in draft mode.</li>
</ul>
Error Page
<ul>
<li>Error 404: This will cause an error page to be blocked from being indexed. As it is an error page, it should not be indexed per se, but just in case.</li>
</ul>
Important note: if you have any doubt about any of the following items it is best not to activate the option as you could lose results in the search engines.
<h3>Compatibility</h3>
<ul>
<li>WordPress: 4.1 – 6.8</li>
<li>PHP: 5.6 – 8.4</li>
</ul>
<h3>Security</h3>
This plugin adheres to the following security measures and review protocols for each version:
<ul>
<li><a href="https://developer.wordpress.org/plugins/" rel="nofollow ugc">WordPress Plugin Handbook</a></li>
<li><a href="https://developer.wordpress.org/plugins/wordpress-org/plugin-security/" rel="nofollow ugc">WordPress Plugin Security</a></li>
<li><a href="https://developer.wordpress.org/apis/security/" rel="nofollow ugc">WordPress APIs Security</a></li>
<li><a href="https://github.com/WordPress/WordPress-Coding-Standards" rel="nofollow ugc">WordPress Coding Standards</a></li>
<li><a href="https://wordpress.org/plugins/plugin-check/" rel="ugc">Plugin Check (PCP)</a></li>
</ul>
<h3>Privacy</h3>
<ul>
<li>This plugin does not collect any information about your site, your identity, the plugins, themes or content the site has.</li>
</ul>
<h3>Vulnerabilities</h3>
<ul>
<li>No vulnerabilities have been published up to version 1.2.0.</li>
</ul>
Found a security vulnerability? Please report it to us privately at the <a href="https://github.com/javiercasares/noindex-seo/security/advisories/new" rel="nofollow ugc">noindex SEO GitHub repository</a>.

noindex SEO

Allows to add a meta-tag for robots noindex in some parts of your WordPress site.

Noindex Duplicate Posts vs noindex SEO