A few seconds ago a first time user of AU asked a question (on AU), which was promptly and correctly answered by @terdon. That question had an exact dupe, equally well answered by @Guss, earlier on Unix & Linux, a SE communities with some overlap with AU and a few other SE communities.

Initially I was actually real surprised that said question was not already answered on AU; on second thought it actually made sense since it already had at least one excellent answer on Unix & Linux.

It made sense, but I would not go as far as saying that before making a query on AU, one should first check whether there is an answer for it in a different SE community. Rather one should learn to post in the right community to begin with. Right, but sometimes it's not so easy to decide as in this case.

  • So, how should one treat a query in a community A, which was already posted in unequivocal terms in community B, both on SE ?
  • Should one call that a dupe or a "cross-dupe", without meaning that the two communities are one but somehow closely related ? I am not sure that sounds completely right.
  • Should flair be awarded per usual, either through upvotes or automatic increment upon acceptance of such an answer to a cross-dupe ?
  • Or should the query echoing another identical query in another community of StackExchange be treated differently in terms of flair accrual, categorisation as dupe, removal, etc. ?
  • Downvote them. Seriously. The fact that we don't have a dupe on AU doesn't mean that you have to create one, less when it's readily available elsewhere, nor that exempt you from searching before asking.
    – Braiam
    Commented Jul 2, 2016 at 18:47
  • @Braiam: You're right that any acceptance of a cross-dupe should not be construed as a license for OP not to do its homework prior to posting. But even though I am sitting on the fence here on whether I would actually go for a little bit of overlap (see JacobVlijm's answer) or for terdon's suggestion to actually promote cross posts on all sites where they are on-topic, I definitely would not downvote a thread that is not straight and blatantly a one-site dupe in the traditional sense. I need to think this out.
    – Cbhihe
    Commented Jul 2, 2016 at 19:56
  • Well, the downvote tooltip says "This question doesn't show research effort...". It ignores intention of the author or otherwise, it just a mean to make sure the OP did it's due homework. I would forgive it if the information was buried or not easily identified (confusing or inaccurate title, for example) but the UL question in this case was in the top of my search results (now's the AU one, due me using the exact title) but he should have find it nonetheless.
    – Braiam
    Commented Jul 2, 2016 at 20:15
  • @Braiam: point taken but only for this particular case where I agree that finding the answer was particularly easy. But it is not always like that, as you point out well.
    – Cbhihe
    Commented Jul 2, 2016 at 20:44
  • 1
    In any case, searching for things like -- is hard. If you're not using Google which keeps track of your favorite webpages, or if you're not one of us geeks who hang out on technical sites, searching for what does "--" mean in the command line doesn't immediately bring the right results.
    – terdon
    Commented Jul 2, 2016 at 22:01
  • @terdon ironically, this specific question doesn't appear either. At least with the UL one you have the symbol spelled out in words which is found ;).
    – Braiam
    Commented Jul 2, 2016 at 22:25

5 Answers 5


Short answer:

I believe cross-dupes not only are acceptable, but a small overlap is even useful:

  • If the scopes of the sites overlap, so should their content.
  • While a minor overlap does no harm at all, a gap between the sites would harm both.

For both sites being useful and complementary, provide an uninterrupted learning curve, the "travel" between them should be smooth.

A minor overlap is part of that. Imagine the situation that you constantly have to switch, because an (on topic) question was coincidentally answered on the other site.


Personally, I think that the best solution would be to develop a way of sharing questions across all sites where they're on topic. The rules against cross-posting were developed back in the days when there was very little overlap between the subject matter of different SE sites. However, things are very different today. The question you mention would be on topic here, on Unix & Linux, on Ask Different, Super User, Elementary OS and maybe more. The current system would allow duplicate questions and duplicate answers across all of these sites.

While I quite agree that this is less than optimal, it's the way things are at the moment. There is no way of flagging cross-site duplicates and no actions mods can take even if such a flag were raised. If you know that the same question has been asked and answered elsewhere, you can feel free to copy it verbatim and post it as an answer here. It would be polite to include a link to the site where you found it, of course, but copying SE answers is very much allowed. We had a discussion on Unix & Linux meta a while ago and that was the conclusion there as well.

So, no, don't flag and yes, copy the existing answer. If you want to be super nice, you can make it Community Wiki so as not to get points for other people's work but, again, that's completely up to you.

  • 1
    Sharing would mean someone is to decide if questions are actually overlappling, and if so on which sites, which makes it unlikely to work. It would also create different "classes" of answers. As a sidenote, I rarely copy an answer 1:1, always like to add additional useful info. Mention the source nevertheless if it is a major part of the answer. Commented Jul 2, 2016 at 18:24
  • 2
    @JacobVlijm the system I am imagining is mods or high rep users of both sites could click a "publish question on site X" button or something, allowing questions to be shared between sites with overlapping scopes.
    – terdon
    Commented Jul 2, 2016 at 18:30
  • Interesting suggestion to actually make sharing answered threads between a limited number of sites where "mods" or "high rep users" know that they also would be on topic. It would enrich other sites at the (modest ?) cost of having to develop the actual tools to do. The receiving site would then have to decide whether the thread is accepted as cross post or whether it represent a cross-dupe. But more work there for mods !!
    – Cbhihe
    Commented Jul 2, 2016 at 19:59
  • @Cbhihe I rest my case ^ :). Also, more options to disagree. Commented Jul 2, 2016 at 20:04

I think a lot of the confusion arises from forums that are very similar. In some cases, a question is on topic in more than one community. In that case, I believe that exact duplicates should stay. I have basically two reasons:

1. Web presence

If the question is correctly answered in two places, the answer will be easier for people to find straight from the search engine or even straight on the site. In other words, whether a person is searching Google for an answer to a question or searching a particular StackExchange community, they will find the information.

2. Bigger database

It also gives each stackexchange communtiy a larger database of information to draw from in the future, preventing further confusion. That is to say, even if you were somehow able to close all these remotely duped questions, sooner or later, it's going to pop up again and you'll have to do it again. Wastes time: poor moderators.

All that being said, I have seen situations arise in which a question is questionably on topic but and is already correctly answered in a community where it is unquestionably on topic. In these cases, my humble opinion is that there should be a means of migrating and duping. Otherwise, it simply promotes re-asking questions in the wrong place; thus promoting disorder and cheating the system.

  • 3
    good point on moderation. So Ocham's razor should first be "It's on topic or it's not"; then whether it is a dupe or not becomes secondary. ---- Somewhere in the back of my head is the fact that the amount of work involved in answering the cross-dupe is far less in any case, provided answerer just got lucky and stumbled upon the earlier answer in the community next-door. So should the reward be the same no matter ? ---- I'm not saying this is what @terdon did in this case. Every one knows that he probably was having dinner and a phone conversation or whatever while answering the question.
    – Cbhihe
    Commented Jul 2, 2016 at 17:49
  • 2
    @Cbhihe ha! What a wonderful excuse. Sure, that's why the first version of my answer had a glaring mistake, 'cause I was having dinner and speaking on the phone! Not because I'm an idiot or anything. :P
    – terdon
    Commented Jul 2, 2016 at 18:01
  • Why where my comments pointing out that asking without research is reason to downvote the questions deleted?
    – Braiam
    Commented Jul 2, 2016 at 22:26

I'm on the fence on this one more leaning toward the some overlap argument as a certain amount of overlap between here and U&L is unavoidable and likely positive, but Braiam does make an excellent point regarding due diligence. As it is, when I run across a question that I know has been answered (and answered well) on another SE site I just comment and point to the related answer rather than wasting valuable time re-answering. In fact if I'm doing MY due diligence I will discover the existing answer on another SE site resulting in the same action as if I had prior knowledge. Sometimes (often?) the question has been answered partially on a number of sites in which case I do my best to pull all the information together and cite the sources. I don't think different methods of determination or handling of cross-dupes are necessary.


I think the best way would be to provide an option to make the same question visible across multiple SE communitites without a need to re-create the question in other communitites (which they are doing now). The answers also can be made visible across the sites. I am saying this because I have myself done that a couple of times just for a straightforward reason: I wanted my question to be visible to more number of people and I found the subject valid in multiple communities.

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