A Link Rot Bestiary/Chapter 5 : Archived Redirect
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Archived redirect or Ghost redirect is redirect link rot. A redirect once existed on the live web and was later deleted. Fortunately while the redirect was live, it was saved into the Wayback Machine, where it's ghostly existence is preserved.
Example: http://www.ew.com/ew/article/0,,286000,00.html is 404 on the live web .. but there is an old redirect saved in the Wayback Machine at https://web.archive.org/web/20150619213058/https://www.ew.com/ew/article/0,,286000,00.html which redirects to http://www.ew.com/article/1998/12/04/twelve-songs-christmas which is the new live URL.
By searching for and discovering archived redirects it is possible to convert dead URLs to live URLs.
A command line tool to automate the above steps is Ghostredir