I have been flagging questions that are cross-posted. Usually this leads to the question being closed; sometimes, my flag is marked helpful but no action is taken and the question is left open. Can I get some clarity on the Cross Validated position on this?

It looks like I've flagged 15 cross-posts in 2020. Of them, about 11 have been closed after being flagged, and 4 have not. Here are the 4 that remain open:

  • Classify tweets per topic - simultaneously cross-posted on 5 SE sites (word-for-word identical; no cross-linking); I flagged, but it hasn't been closed.

  • Model of dithered lattice quantization error/noise - simultaneously cross-posted on one other SE site (word-for-word identical; cross-linked); I flagged twice, but it hasn't been closed.

  • Comparing a large/general CNN to a smaller more specialized one? - simultaneously cross-posted on one other SE site (word-for-word identical; no cross-linking; answered on the other site); I flagged, but it hasn't been closed.

  • the probability of random subset - cross-posted on one other SE site (word-for-word identical, no cross-linking; slight differences in typesetting; answered on the other site; also re-posted here on Stats.SE a second time, and answered that second time); I flagged, but it hasn't been closed.

I'm not sure how to interpret the differing responses. Do the moderators want cross-posted questions to be flagged? Do you want me to stop flagging them? Is this a difference in the views of different moderators? Is this an oversight? Should I be re-flagging if they are't closed on my first attempt, on the theory that perhaps my custom text was not sufficiently clear?

Have I misunderstood some aspect of Cross Validated's policy? The SE-wide default policy is that cross-posting is discouraged or prohibited (and to the extent that there is any wiggle room, it seems pretty clear that cross-posting word-for-word identical questions is not the way to go about it). The policies that I can find articulated on this meta seem similar: see, e.g., 1, 2, 3, 4, 5. My preference and request would be for moderators to close cross-posted questions when flagged, but if moderators are aware of cases or criteria where they don't plan to do that, it'd be helpful to know that, if possible, so I don't waste your time or my time raising unwanted flags.

  • 4
    $\begingroup$ Thanks for taking the time to raise this matter. My practice has been to ensure that links are provided to the cross-posts & that OPs are aware that cross-posting is discouraged - but I don't usually go so far as to delete posts that are squarely on-topic here unless someone's making a habit of cross-posting. It's worth a Meta discussion to determine what CV users want & to make sure we're fairly consistent. $\endgroup$ Jan 6, 2021 at 9:15
  • $\begingroup$ @Scortchi-ReinstateMonica, Thank you for letting me know your practice. I would be interested to hear about the position of other moderators as well. And, if not all moderators take the same position, is it OK for me to re-flag if I don't like the outcome I got from one moderator? A note of clarification: I am talking about closing, not deleting. I consider that an important difference, because someone who finds a closed copy and wants to answer can always follow the link to the other copy that is open and answer over there. $\endgroup$
    – D.W.
    Jan 6, 2021 at 9:20
  • $\begingroup$ We shouldn't take different positions! We'll see what the outcome of the discussion here is & then you won't need to re-flag anything (unless the decision doesn't seem consistent with what's been decided). I'll try & post an answer (arguing for a fairly liberal, case-by-case approach) this week. $\endgroup$ Jan 6, 2021 at 9:40
  • $\begingroup$ By the way - would it be all right to post links to any of the other posts you've flagged as cross-posted, the ones that remained closed? It could be of interest to compare outcomes - I notice that I plus one other moderator left the ones you link to open, & none have yet been answered here, $\endgroup$ Jan 6, 2021 at 9:59
  • $\begingroup$ FWIW, my policy, when I was a mod, was to close the threads. $\endgroup$ Jan 6, 2021 at 12:39
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    $\begingroup$ Although cross-posting is discouraged on SE, it is not forbidden. I do not close questions solely because they might be cross-posted, but I do evaluate them with less lenience. For instance, if a question has been cross-posted on Math and has a good answer there, then if that question is not squarely, obviously on topic here I will close it. I appreciate flags that point out cross-posts and I hate to reject those flags, but the system doesn't provide any other option than accept or reject. $\endgroup$
    – whuber Mod
    Jan 6, 2021 at 13:54
  • $\begingroup$ D.W., would you suggest the post should always be closed on CV rather than on the other site? Otherwise it is a question of which of the duplicate posts should be closed. Perhaps it is the other sites that should be closing those duplicates. If you got as many as 11 of 15 closed here, perhaps the remaining ones should be closed elsewhere? $\endgroup$ Jan 6, 2021 at 16:04
  • $\begingroup$ @Scortchi-ReinstateMonica, sure, that's fine. Would you like me to update my post with those links? $\endgroup$
    – D.W.
    Jan 6, 2021 at 17:15
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    $\begingroup$ @RichardHardy, no. When I see something that has been cross-posted to N sites, I try to form a subjective judgement, and then flag it on N-1 of the sites (except where I know from experience that a site tends not to act on those flags). There were other posts that were cross-posted here that I didn't flag here because I thought here was the best place for them; instead I flagged them elsewhere. $\endgroup$
    – D.W.
    Jan 6, 2021 at 17:17
  • $\begingroup$ I see. It might be that the moderators thought differently and decided the post fits best on CV and should instead be closed somewhere else. And perhaps they did not act on the latter thought. $\endgroup$ Jan 6, 2021 at 17:46

3 Answers 3


Once links to the cross-site duplicates have been provided, there doesn't seem to be a pressing need to close the question if it's squarely on-topic at this site; potential answerers can now decide whether or not they want to write an answer in full cognizance of actual or potential answers elsewhere, as @mdewey's answer points out. (The notion that a question should be on topic at one site only seems very dated now; plenty are on-topic at several without any need for "tailoring".)

And once the OP's been informed of the cross-posting policy, shouldn't they be given the chance to decide on which site they want the question? It's perhaps a little heavy-handed to immediately decide for them.

Another issue that sometimes arises is that even a currently unanswered question is part way along to getting an answer—there are comments asking for clarification, edits in response to the clarification—& it would be a shame to throw that work away.

All in all I feel it's better to deal with the flag by taking the opportunity to weed out poor questions & to check on the OP's other posts (such flags are certainly helpful), & otherwise just ensuring that the necessary links are there & that the OP's now aware of the policy.

† That's not to say we should jettison the policy: the consequences of allowing cross-site duplication en masse might still be unpalatable.

‡ A repetition, though, should be dealt with by closing/deleting the question.

  • $\begingroup$ It sounds like this proposal amounts to keeping the policy on the books in principle but not in practice, by treating it as an ideal but usually not enforcing it. In what ways is that a fair summary and in what ways is that unfair? $\endgroup$
    – D.W.
    Jan 11, 2021 at 16:57
  • $\begingroup$ To respond to your specific comments: (1) giving OP the choice: I've tried that but my experience is that most OP's never respond if the questions are left open; if OP's do respond and the wrong one was closed it is easy enough to re-open and change which one is closed; (2) my perspective is that it is the cross-posting that causes the wasted work; closing all but one allows those to be focused on a single question in the future, whereas leaving them open continues to fragment edits and comments and leads to more wasted work; $\endgroup$
    – D.W.
    Jan 11, 2021 at 17:01
  • $\begingroup$ (3) regarding question quality, my sense is that it'd be more useful to refocus askers on improving the quality of their question rather than the quantity of sites they reach (and if they do that, it can also address the issue of wasted work). $\endgroup$
    – D.W.
    Jan 11, 2021 at 17:07
  • $\begingroup$ @D.W.: A little unfair, perhaps: most people won't continue to cross-post when they've been asked not to, & I wasn't suggesting no action should be taken against those that do. (I'll edit to clarify the latter point.) $\endgroup$ Jan 11, 2021 at 19:09
  • $\begingroup$ Got it. So is your proposal/position that a person's first cross-post might not be closed, but if they cross-post a second time (after receiving a comment indicating that they should not cross-post the first time), then moderators will close the second one? Is that an accurate understanding? $\endgroup$
    – D.W.
    Jan 11, 2021 at 19:52
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    $\begingroup$ @D.W.: Yes, close, or delete, or even suspend the user if they refuse to stop cross-posting (believe it or not, this has in fact happened). $\endgroup$ Jan 11, 2021 at 19:56
  • $\begingroup$ OK, thank you for helping me understand how you plan to handle this. Are there any other criteria? For instance, whuber mentions that if the question has been cross-posted and has a good answer elsewhere and isn't "squarely, obviously" on-topic here, he'd close it; is that something you plan to follow as well? $\endgroup$
    – D.W.
    Jan 11, 2021 at 20:03
  • $\begingroup$ @D.W.: Yes, that approach is the one I try to follow; what I plan to follow depends on the outcome of this Meta discussion. You make some good points above (1-3) - if you have time you might roll them up into an answer (if you don't I can put them in my "firmer line" answer). $\endgroup$ Jan 12, 2021 at 9:05

From my point of view the main reason I dislike cross posting is the potential waste of my time and that of other users answering some question which has already been answered elsewhere. Given that the comments which the OP has posted specifying the cross posts are very helpful as I would not answer any question where I saw such comments. It seems less necessary to also close the question as if someone wishes to proceed to answer it in the knowledge that there may be duplication of effort then that is their privilege.


If we want to take a firmer line:—

Moderators can close the cross-site duplicate using a custom reason (neater than using an inappropriate default close reason). If we think there's value in keeping it here purely to link to the duplicate on another site, we can up-vote it, which will protect it from automatic deletion. In fact any user can vote, up or down, so an advantage of this approach is that the decision isn't made by a single person.


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