Frank Bueltge

Inpsyde GmbH

When you change the permalink structure then this is a problem for bookmarks of users and also for search engines to link to your posts. This plugin uses the slug of the new url and search for a ID in the database of WordPress. If it finds a post according to the slug, the Plugin will redirect to the correct post and send a header message “moved permanently 301” to change the url on the index of search engines.

Change Permalink Helper

Awesome!

It checks the Permalink and redirects to the new URL, if it doesn't exist. It sends the header message "moved permanently 301"

keith graham

The Link Fixer Plugin (note the name change from Permalink Finder) detects when WordPress cannot find a permalink. Before it generates the 404 error the plugin tries to locate any posts with similar words. It does this by searching through the database trying to find any of the word values from the bad link. It takes the best match and then, rather than issuing a 404 error, it sends back a redirect to the correct page. 
Users will see the page that they are looking for, and search engine spiders will see the 301 redirect and update their databases so that the page appears correctly in searches.
The configuration panel allows a user to select how the plugin finds a missing page. The plugin counts the number of words that match to a post. By default, a two word match is sufficient to cause a redirect to the found page. False positives are possible, especially if the user selects a one word match. Increasing the number of words, however makes it unlikely that the plugin will ever find a match. You may eliminate numbers from the search. You may specify that a list of common English words like “the”, “and”, “who”, “you”, etc., not be considered in finding the correct permalink.
Optionally, the plugin will redirect hits on index.html, index.htm, and index.shtml to the blog home page. This is useful when a website previously used a non-php home page.
If WordPress detects a 404 error on robots.txt, sitemap.xml, crossdomain.xml, favicon.ico, or apple-touch-icon.png it will provide a default version.
The plugin will also optionally keep track of the last few 404’s or redirects. This is useful to find out what pages are missing or named badly that keep causing 404 errors or forcing redirects.
<h3>Support</h3>
This plugin is free and I expect nothing in return. Please rate the plugin at: https://wordpress.org/extend/plugins/permalink-finder/ 
If you wish to support my programming, You can donate or buy my book: 
https://linktr.ee/keithpgraham

Link Fixer

Never get a 404 page not found again. If you have restructured or moved your blog, this plugin will find the right post or page every time.

Change Permalink Helper vs Link Fixer