Dead Link Checker — Find the Links That Stopped Working
This follows the links on a page or across a site and reports which no longer resolve, along with the ones that redirect. Links decay without anything on your side changing: an external site restructures, a page you linked to is removed, an internal route is renamed in a refactor that missed one reference.
When it helps
Because nobody clicks their own old links. A broken link in a navigation menu is found immediately; a broken link in a two-year-old article is found by a reader, or by nobody, and it is quietly costing you both credibility and whatever that page was meant to lead to. Internal broken links are worse than external ones, because they are entirely your fault and entirely fixable, and they are usually the residue of a rename.
Worth running automatically
This is decay rather than breakage, which means there is no event to react to and it will never be urgent. That is precisely why it needs a schedule — a task that is never urgent is never done. Running weekly and reporting only the newly broken links keeps the output small enough to act on, which is the difference between a report that gets read and a list of four hundred links that gets ignored. Watching redirects is worth including, since a link that now takes two hops is a link that will eventually take none.
What you get out of it
Finds the links that broke after you shipped, which is nearly all of them. The scheduled version is the only version that works, because the task is never urgent enough to do by hand.