Are cross posts to Math SE allowed? As in almost exactly the same text, just posted there. Of course the sites are meant for difference things, but still just wondering. And if yes, should one link the MO post before posting on Math SE?


1 Answer 1


If you have posted a question at MSE and want to cross-post it at MO or the other way around, you can do it under the following conditions:

  1. Wait several days, not just hours. I would suggest a week.
  2. Provide links between the two versions. The MO question should have link to the one at MSE and vice versa. (This is for honesty and avoiding duplicate efforts for those who answer.)
  3. Make sure the question is on-topic at the new site.
  4. If you have received helpful comments for the old question but no answers, take them into consideration when posting here.
  5. MO and MSE require different merits for questions to be well-received. Not only are the scopes different, but also the communities value different kinds of background information.

These conditions reflect what I believe to be a consensus of some kind, but some people might disagree.

I think you should not cross-post instantaneously. If you realized that you asked in the wrong place and there are no answers yet, simply delete the old one and ask in the right place.

  • $\begingroup$ As I understand, the OP asked about cross-posts the other way round -- namely, whether cross-posting an MO question on Math.SE is allowed. Anyway, it seems your answer answered the question satisfactorily. $\endgroup$
    – Stefan Kohl Mod
    Commented Dec 5, 2015 at 20:50
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    $\begingroup$ @StefanKohl, you are right. I think the same ideas work both ways, so I tried to edit my answer accordingly. (Can I get away with understanding a question the opposite way because I work with inverse problems?) $\endgroup$ Commented Dec 5, 2015 at 21:10
  • $\begingroup$ @Stefan: This has absolutely nothing to do with the "direction" of the cross-posting. This has to do with the fact that cross posting is bad. See my falafel analogy. $\endgroup$
    – Asaf Karagila Mod
    Commented Dec 5, 2015 at 21:15
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    $\begingroup$ Is it possible to make that when somebody wants to cross post something, the program remids him these rules? $\endgroup$ Commented Mar 28, 2016 at 14:57
  • $\begingroup$ @SergeiAkbarov, I don't think that's currently possible. If you would like to see such a feature, you can post a separate feature request (question using that tag) at meta. I would like to see something like that in action, but it might be hard to implement. $\endgroup$ Commented Mar 28, 2016 at 17:08
  • $\begingroup$ Yes, I understand... OK, thank you. $\endgroup$ Commented Mar 28, 2016 at 18:04
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    $\begingroup$ Joonas, I asked this in Meta: meta.mathoverflow.net/questions/2814/… $\endgroup$ Commented Mar 29, 2016 at 6:11
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    $\begingroup$ I have incorporated much of Joonas' excellent answer into this answer discussing cross-posting to other sites more generally (not necessarily just to Math.SE). $\endgroup$
    – Tim Campion Mod
    Commented Apr 23, 2021 at 23:37

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