I found so many web links became invalid on the questions and even more on the comments. Please be aware of this issue. In the future, this site needs to either repair the invalid links or advise users not to use the web links.

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    $\begingroup$ You can use the Wayback machine to figure out where the link used to be pointing, then when you find the relevant source, add an updated link. $\endgroup$ Mar 13 at 17:09
  • $\begingroup$ I think this site would be considerably impoverished if people couldn't link, and it's hard to know how the site could automatically repair invalid links. So it's hard for me to see what action this question is suggesting. (In tems of "please be aware of this issue", as @MartinSleziak points out, I think most of the MMO audience probably already is.) $\endgroup$
    – LSpice
    Mar 18 at 19:48
  • $\begingroup$ Something I've begun doing the past few months (but not recently enough for any of my "recent" mathoverflow answers) is to save the page at the Internet Archive, and then use the archived URL (unless a Stack Exchange link, or Wikipedia link, or something else unlikely to go dead in the foreseeable future). Most recently I did this for a link I gave following “Example 3: Evaluate a Mixed Composition of Trig Functions” in this MSE answer. (@Martin Sleziak: In case interested.) $\endgroup$ Mar 23 at 18:42
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    $\begingroup$ @DaveLRenfro Your comment reminded me of this old post on Mathematics Meta: Should we try to prevent link rot? $\endgroup$ Mar 24 at 10:25
  • $\begingroup$ @Martin Sleziak: It appears I saw your old post at that time, as I have a comment to an answer there. It's strange, but while reading my comment (there) just now, I recall writing it, but I would have guessed I wrote it 2 or 3 years ago, not nearly 9 years ago. $\endgroup$ Mar 24 at 10:38

2 Answers 2


I think that many people around here are aware of problems with dead links and they do their best to help. (And the same is true about many other sites on the Stack Exchange network.)

One thing is that it is recommended to add sufficient information about the referenced paper - so that even if the link no longer works, the readers are still able to identify the relevant text. See, for example, the advice given here: Citing papers in questions/answers.

And in many cases where links stop working, the users around here help with updating them. Discussions which are - at least to some extent - related: Any policies around Dead links? and Is it worth editing old posts to add links for references?

The chatroom Boulevard of broken links is devoted to this issue. Although it is associated with Mathematics Stack Exchange, fixing links on MO is discussed there sometimes, too. A brief description of this room is given in this answer. (Meta Mathematics Stack Exchange even has a separate tag for discussions concerning dead links.)

Among the rooms associated with MathOverflow, the room called MO editors' lounge is related to editing posts - which includes fixing dead links. This room was created by quid as announced here.


Let me add to Martin's answer that part of the problem is people posting their answers as comments. Questions and answers can be edited and updated automatically when a server changes address; comments cannot, and the broken links stay broken forever.

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    $\begingroup$ Moderators can edit comments, even if the original users cannot. If nothing else, users (with the required small amount of rep) can make a subsequent comment with the correct link $\endgroup$
    – David Roberts Mod
    Mar 29 at 1:35
  • $\begingroup$ @DavidRoberts Thanks, I wasn't aware! Can you also do it automatically, for instance if Arxiv wanted to change its website to arxiv2025.org can you edit all instances with O(1) human time instead of O(n) where n is the number of comments that contain that address? $\endgroup$ Mar 29 at 7:18
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    $\begingroup$ Presumably SE can do such things, but I don't believe we mere moderators can $\endgroup$
    – David Roberts Mod
    Apr 11 at 3:51

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