It is natural that some of the links in the posts stop working eventually. In some cases, the dead links are fixable. (And there are many editors on this site who try to edit such links.)

Perhaps we could collect here on meta various domains (that are often used in the posts on this site) where the links stopped working - but which can be corrected. We could split them into links that:

• Can only be corrected manually.
• Can be corrected in bulk by the search and replace tool.

Since Stack Exchange CMs sometimes do correct links in bulk, at least in some cases this could be used to fix the links without bumping any posts. (If we can find several domains which need correcting, it might save a bit of time for SE employees, if we ask for correcting all of them at once.) And even for the links which can only be corrected manually, having a list with a brief explanation how the links can be corrected might be useful.

Some stuff related to fixing dead links can be discussed also in the chatroom Boulevard of Broken Links.

More details on what can/cannot be done using the search-and-replace tool available to the Stack Exchange staff (which can "edit" posts without bumping):

I will add links also to some requests for mass replacements on other per-site-metas — just in case some useful information can be found also in those posts:

• A couple of instances on our own Meta regarding such broken links: (1) Link Rot Notice: Springer EOM, and (2) Old Links to PlanetMath have Broken. Apr 14 at 11:53
• I have a tangentially related idea of creating a chatroom ("Boulevard of Broken Links") to feed and triage Comments reporting broken links. Crude experiments with SEDE suggest about two dozen such Comments are posted per month. My guess is that some will be related to the domain-based issues Martin describes here, while others will have an idiosyncratic nature. Apr 14 at 16:59
• Martin, this is lovely. Thanks for all your efforts and all you do to help maintain this website. Apr 14 at 19:23
• Sigh, what happened to "cool urls don't change" ... Apr 15 at 20:15
• The chatroom Boulevard of Broken Links (mentioned in a comment above) has been created on 2022-04-15. Apr 16 at 18:10
• This can help? (didn't read the whole question above,so forgive if it doesn’t help) Apr 18 at 13:45
• Glorfindel has a Broken Link Repairer script, which is mentioned here: meta.stackexchange.com/a/375122/334566 Apr 27 at 11:12
• @PM2Ring Yes, Glorfindel mentioned this script recently also in connection with the broken projecteuclid links. Of course, this is a bit different from the bulk removal by the SE staff - edits by this script bump the posts, just as edits by a regular user. Still, it can be used for some other edits which can be automated - but which are beyond the possibilities of the SE's search-and-replace tool. Apr 27 at 13:11
• @Martin Ah, so Glorfindel is already in the loop. Excellent. :) Apr 27 at 15:56

• The links containing http://math.uga.edu/~pete do not work. There are some exceptions, but in most cases it would be enough to change the beginning of the URL to http://alpha.math.uga.edu/~pete. (One case where it does not work that I saw was that the link http://math.uga.edu/~pete/expositions.html doesn't work after this modification, as far as I can tell, the page has been moved to http://alpha.math.uga.edu/~pete/expositions2012.html. Still, the links could be corrected in bulk — but either after the mass replacement or before, the "wrong" links should be corrected manually.) At the moment (April 2022) I get 561 posts from search and 567 posts from SEDE. (SEDE — last activity, SEDE — already edited) Added later: Now there is a separate post asking to replace those links in bulk - if/when that is done, this bullet point will become obsolete: Suggestion to mass-replace links to http://math.uga.edu/~pete.