This is used inline beside (to the right) of a broken external hyperlink to signify to editors that the hyperlink in question is dead.
It is suggested to update the link if possible, perhaps using archive.org.
List of all articles with at least one marked dead link
All http:// hyperlinks. All of these need to be checked to see if they can be rewritten to https://
All ftp:// hyperlinks. All of these need to be check to see if an sftp:// or https:// version is available.
All https:// (modern web) hyperlinks.
All irc:// hyperlinks. There shouldn't be any. Links to libera or OFTC should be ircs://
All ircs:// (modern IRC over TLS) hyperlinks.
All mailto: (email) hyperlinks.
raw wiki markup: