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It is possible to migrate a question from one Stack Exchange site to another by closing, but if I have a question that I think is on-topic for multiple Stack Exchange sites, is it OK to post it on both (multipost)?

For example, I have a question that's earned me the tumbleweed badge on SO and I'm not sure what the best thing to do with it is. It's about a web server so it might be answerable on Server Fault but it's really more of a programming thing, hence the posting the question on Stack Overflow.

Is there any way to make the question visible on multiple sites (crosspost) and then accept the answer wherever it came from?

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As a general rule: No.

Ask the question on the site you think is most applicable. Each site is focused on a specific topic area and it's important to respect the community. Reading a sample of well-received questions can give you an idea of what's on topic. Look over the site's /help/on-topic guidance before asking, if you still aren't sure.

If your questions does not get a useful answer, consider editing the question based on comments and other feedback. If that doesn't help, you can always set a bounty on your question, which will give it much better exposure. This will also mean you have a better chance at getting a good answer.

Occasionally, people are interested in different perspectives on the same fundamental question. There are many Stack Exchange sites with overlapping topic spaces and it can be useful to get a "second opinion". Even then, however, it's best to tailor your question to each site. Ideally link to the question on the other site and explain what you hope to learn from asking another community.

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    But what about writing the same question in 2 different languages? Eg. Post in Portuguese SO and International SO. – LeonanCarvalho Jul 12 '17 at 18:27
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    What is the correct way to handle identical posts across SE/SO sites? Flag a mod? – ashleedawg Feb 21 '18 at 8:05
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    what about questions about interdisciplinary topics? I have a question about differential geometry and quantum computation, and I see no reason why the question couldn't be asked in both the math and physics site. – Guillermo Mosse Nov 14 '18 at 13:51
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Allowing cross-posting is a slippery slope.

If you might have slightly better odds of getting an answer by posting it on two sites, well, by gum, why not maximize your odds by posting it on twenty sites!

There are some questions which fall into grey areas between sites, and I think it's OK to ask and delete, then re-ask if you feel you have asked on the wrong site.

But as a general rule, do not cross-post questions, please. Pick a site and go with it.

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    +1 Murphy's Law. Just because you gave the same answer I did, in shorter sentences, your going to get all the darn upvotes! :) – BinaryMisfit Sep 10 '10 at 8:47
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    While I can imagine the same question to be on-topic on the math site and the physics site, I don't think the same question could then be on-topic also e.g. on the bicycles site, the cooking site and the photography site. So I consider the slippery-slope argument invalid. – celtschk Sep 23 '12 at 14:23
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    It's a slippery slope if not managed by the community well, but the same goes for the Q&A's themselves. It's no reason to rule it out. If it's implemented and managed well, cross-posting could make a great feature for the network and increase cross-site collaboration. See my comment above: meta.stackexchange.com/questions/64068/… – Charles Roper Oct 5 '12 at 8:06
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    Slippery slope is a manipulation method. It is slippery slope to allow users to specify 5 labels (tags) in their posts. Why not 25? Think about it. Manipulation is what you use here. There is nothing slippery for a thing to belong to 25 categories at once. What you do here is trying to justify your magic numbers not as arbitrary rule but as something deeply grounded and suitable for all cases. No, it is not a best fit for all cases. The more categories you create, the less probable that particular case will belong to only one of them. – Val Jun 9 '13 at 12:02
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    @val if we allowed 25 tags, there would be 2 decent tags on a question and 23 noise tags. The net result would be a polluted and useless tag system. Without constraints, people make bad choices. See: George Lucas and Star Wars Episodes 5+. – Jeff Atwood Jun 10 '13 at 17:32
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    @JeffAtwood Nevertheless, you slippery slope when allow multiple labels per post. I can agree that you can order categories in terms of their appropriateness and get a decaying curve. If decay is fast, a couple of first categories cover most of the area under the curve. But, if distrubution is almost uniform, as it happens when you do not know where to relate the subject, you'll need to pick much more best candidates to cover the field with good probability. The point is that when you have many categories to choose from, making a good coverage will need including more categories. – Val Jun 10 '13 at 18:51
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    -1 because you made a slippery slope argument and you even used the phrase "slippery slope". – Parthian Shot Aug 4 '15 at 0:06
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    "why not maximize your odds by posting it on twenty sites!" Because no question would be on-topic at 20 SE sites. No need to delete a question if you didn't receive an answer on one site though, since it will move you closer towards a question ban and there is still a chance someone may answer in the future. – pacoverflow Dec 9 '16 at 17:24
  • @ParthianShot - Nice link! – sancho.s Sep 25 '18 at 8:21
  • @CharlesRoper - See the link provided by Parthian Shot, rationalwiki.org/wiki/Slippery_slope – sancho.s Sep 25 '18 at 8:23
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Very occasionally you may want to ask substantially identical questions on two sites, to reach different communities. (For example, if you're looking for a computer application to perform a certain task, and you don't mind whether it's a local application or a web application, you might ask on both Super User and Web Applications).

This is the exception rather than the rule. The question you ask has to be on-topic on both sites.

Again, if it's your question and you want it moved on second thoughts, flag a moderator and request a migration.

If you really think your question belongs on both sites, it probably doesn't.

If you really really think your question belongs on both sites, link the questions to each other. (If it's not your own question on one site, you might just leave a comment.) This way, people won't waste their time duplicating an answer already written on the other site, and people who find the question later can read both sets of answers.

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    this can be OK, so long as the question is tailored to each audience on the different sites and is materially different in each case. Just to be 100% clear, copy-pasting a question across sites with no changes is considered abusive behavor. – Jeff Atwood Jan 15 '11 at 3:51
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    User uses Unix community to ask why he should not type passwords into the command line, unix.stackexchange.com/questions/78734/…. I wonder why not in the security and what need to be tailored for the security? It is a purely security question and security aspect of the Unix. It is a specific aspect of the specific system. Why should one tailor anything? What needs to be tailored when you ask about complexity theory in signal processing? Should I ask about z-transform in comp.sci, control theory, dsp or math, which covers them all? – Val Jun 9 '13 at 11:46
  • @Val: The user wishes to know how the information will leak; all of the answers are highly specific to how Unix leaks the information. If the user had asked on security, the answer might have been, "because the information might leak." However, the user already knows that; they wanted to know how it would leak. In this case, security is an inferior place to ask that question; only Unix experts know the answer, but security experts often don't. – Brian Dec 27 '13 at 13:59
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    @Brain You have just convinced us that one label/tag is enough for a question. It is not. I am not convinced. Ok? Even if I provided a wrong example (which I think I was not because command line and strong passwords in user files is not something specific to specific OS, ok?), you should argue the general case. – Val Dec 27 '13 at 14:12
  • I think I managed to make this advice work for me, though the original wasn't my question, and the transition was a little rough for other reasons, to say the least...Thanks for helping to make it possible! Good answers from distinct perspectives on each version. – Nick Stauner Feb 7 '14 at 19:13
  • Note about the example: If you are looking for an application, then the question is probably only on-topic at Software Recommendations. – Nicolas Raoul May 10 '16 at 1:45
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    @NicolasRaoul No, this is not true. Stack Overflow and Super User are allergic to software recommendations, but many other sites aren't. – Gilles May 10 '16 at 11:11
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One problem is the wide disparity in attention levels at different sites. Is 39 moves the longest a chess game can go moving only pawns? was posted to Math. I think it is a much better fit for Puzzling, but the activity level at Puzzling is so much lower. Cross-posting would help in cases like this.

The proliferation of sites (particularly betas) makes this disparity a frequently recurrent issue and puts the growing Stack Exchange network somewhat at odds with a strict policy against cross-posting, especially in the long run as topic overlap increases.

Some wiggle room could help release a lot of this tension. Consider supporting related feature requests (see the comments for many more) and encouraging conscientious cross-posting practices (see @Gilles' answer here and Shog9's here) rather than simple discouragement. If done right, it could help build nascent communities and collaboration among them. To connote more positivity to the productive practice with an alternate buzzword, one could think of it as cross-pollination.

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    See also Robert Cartaino's answer on "What to do with cross-site duplicates?": In the edge case where the question is appropriate on more than one site, leave it on both sites and let the users of each community benefit from the information. These were edge cases five years ago, but are they still rare now? – Nick Stauner Jul 30 '14 at 20:56
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    No one seemed to mention this very important point of comparisons in site traffic, +1. – bmende Apr 30 '16 at 23:45
  • +1 for the concept of cross pollination for (and I would add eventual migration to) betas. If the idea isn't to always reduce questions to their minimum viable community, then why have separate SE sites at all? – virtualxtc Apr 26 '18 at 22:47
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This should help those of you who, like me, couldn't understand why cross-posting is discouraged, when one's intentions are good (an interest in getting the expert opinion of two diverse communities regarding a question that is on topic for both).


I've discussed the no-cross-post debates over the months and I never could understand what was wrong with posting an identical question on two sites when it was perfect for both sites as-is. A question that I thought was fair to cross-post was:

  • Valuable to both communities
  • Worded perfectly for both communities without any change or "tailoring" needed
  • with the intent of getting two diverse kinds of answers on the question
  • not just to get an answer faster

This belief was confirmed by answers like this:

In the edge case where the question is appropriate on more than one site, leave it on both sites and let the users of each community benefit from the information.

However

Here's the real underlying problem: The SE Network was not designed for duplicate questions across sites. That's the issue to which there's really only one simple solution: don't post identical questions.

Because the SE Network is designed to work as a unified tool, combining questions from all sites, identical posts are oddballs.

With the way the Stack Exchange network features questions from different sites, if we didn't discourage cross posting (even when the question is very much on topic in both places), we would see duplicate questions featured on the front page, which would look a bit weird.

The whole "It's ok if you tailor your question to fit each site" idea, which is now quoted/referenced in all related meta discussions, originally came from Jeff Atwood himself (see his answer), and that solves the duplicate issue. Other than that, there's really no issue with duplicate questions, as long as they're good questions totally on topic for both sites.

Some questions can be perfectly on topic for two sites with identical wording, but the network was simply not designed to handle duplicate posts. Change the wording and tailor the title, even if it's already good for both sites - just make it different (This argument assumes that the question is truly good for both sites) and it's ok.


To anyone who says duplicate questions a bad in all cases, that's simply wrong! When questions are cross-posted with the right reasons in mind, in the right situations, there's nothing wrong with them, except the issue that I mentioned (the SE network's unified functionality).

So when you discourage users from cross-posting when the question fits well on two sites, explain this to them. It's not that the "tailoring to each site" is always necessary, it's just that duplicates don't work well in a network where questions from all sites are featured on the same page.

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    FINALLY! An answer that makes sense. (Okay, I'm a bit slow to find this.) SE should be thought of as a "team" of distributed sites where a submission to one is really, eventually, a submission to all. As a former DBA, I get it now. Wish this answer got more love. I think it would greatly reduce the amount of cross-posting by folks (like me) that don't understand why it is both unnecessary and disruptive to maintaining a high quality database of information. Thank You @CuriousProgrammer ! – DocSalvager Feb 20 '16 at 5:27
  • What a nonsense. Internet is not designed to handle duplicates. Neverless, you make them because it is designed in a way that one community is isolated from another. When you say that you would see the duplicate questions, you basically mean that all communities see questions from all other communities. Who are you trying to cheat? The cross posting is desirable just because your statement is not true. People have to cross post in order to address the question to another community, which is isolated from first. The problem would be solved if we had only one site with community-specific tags. – Valentin Tihomirov Mar 13 '16 at 13:57
  • @ValentinTihomirov now that was some nonsense. – Viziionary Mar 17 '16 at 3:42
  • The first part of the answer has solid grounds on arguments aiming at "being useful for the community". Then it comes an argument-almost litany-with little orientation towards being useful. This looks to me, in short, as "The essence of two questions posted in different SE sites can be exactly the same, but they have to be differently worded to be admissible". That, for me, is like encouraging make-up on the wording so they do not look awkward... appearances above meaning. For me, this should be frowned upon. – sancho.s Sep 25 '18 at 7:56

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