jfoucher

This plugin uses the yahoo.com API to find the most relevant keywords from the content of your post, and then adds them as tags.
The tagging is fully automatic, so if you’re using a plugin like feedwordpress to display RSS feeds on your blog as posts, everything will get done as the feed posts are published. No user intervention necessary!

Auto-tags

Automatically add relevant tags to new posts.

Bernhard Riedl

This plugin is a <a href="https://www.bernhard-riedl.com/2010/08/01/tagpages-tags-functionality-for-pages-in-wordpress-30/" rel="nofollow ugc">follow-up</a> to the post which I wrote <a href="https://www.bernhard-riedl.com/2007/10/06/wordpress-23-tagging-posts-and-pages/" rel="nofollow ugc">a few years ago</a>. – The idea was (and still is) to equip pages with <a href="https://en.support.wordpress.com/posts/tags/" rel="nofollow ugc">tags</a> and include their number in a combined posts and pages <a href="https://codex.wordpress.org/Function_Reference/wp_tag_cloud" rel="nofollow ugc">tag-cloud</a>.
TagPages is fully compatible with <a href="https://codex.wordpress.org/Administration_Over_SSL" rel="nofollow ugc">https/SSL/TLS-sites</a> and WordPress multisite network.
Plugin’s website: <a href="https://www.bernhard-riedl.com/projects/" rel="nofollow ugc">https://www.bernhard-riedl.com/projects/</a>
Author’s website: <a href="https://www.bernhard-riedl.com/" rel="nofollow ugc">https://www.bernhard-riedl.com/</a>

Auto-tags vs TagPages