Auto Internal Linking by Kuantero is a WordPress plugin that automatically inserts internal links based on post tags. When a post contains a tag “X”, every occurrence of the word “X” (only in non-linked content) across your site—except on the homepage—will be automatically linked to the most recent post that also uses that tag. The plugin avoids self-linking (a page linking to itself) and only processes up to two link insertions per tag per post. Manual links remain unchanged. The settings page in the admin area displays statistics on how many posts/pages were modified for each tag.
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First, you need to have tags on a post, that you want to promote via SEO
Second, if that tag is present on other posts in content, an internal link will appear towards the initial page that specified the tag