So it's crossed my mind recently in relation to a few of my questions that they would be quite appropriate on more than one Stack Exchange (Area 51) sites. My question is, is it considered acceptable/appropriate to post an identical question on, say, two different SE sites?

To give a concrete example, I recently asked the question entitled The Power of Lambda Calculi on math.stackexchange (Mathematics), but soon thereafter it would be almost as appropriate on cstheory.stackexchange.com (Theoretical Computer Science).

Any thoughts on this general issue (or even specific case)? Should users be permitted (or even encouraged) to cross-post in certain rare cases where the subject matter is germane to more than a single SE site?

Note: See the related FAQ entry here


3 Answers 3


Cross posting is fine, provided:

  1. You respect the differences in the audiences at the different sites;
  2. You allow some time to pass between successive questions, and update them in the light of the answers previously received; and
  3. Really the first point again, you should have an idea what the new site offers in terms of expertise to crack your question that the previous site did not.

Usenet-style forum spamming is, I hardly need to say, bad.

  • Hi Charles. Thanks for the info. Funny that you've answered my question and now meta-question! Is that an official Stack Overflow line on cross-posting? Either way, it agrees exactly with the common-sense answer I had in mind.
    – Noldorin
    Commented Sep 28, 2010 at 18:23
  • @Noldorin: I saw your question here first. Is that an official Stack Overflow line on cross-posting? - No, but it reflects widespread practice among SX betas and MO. Commented Sep 29, 2010 at 13:33
  • Well, whatever gets your attention. :) And fair enough regarding the practice, sounds sensible to me.
    – Noldorin
    Commented Sep 29, 2010 at 16:00
  • how much time is some?
    – Lee
    Commented Jul 5, 2017 at 16:47
  • @atomh33ls - I'd recommend two days, less if high-reputation people at the site say that you are likely to get better answers somewhere else. Commented Dec 13, 2019 at 16:27


If you have {x} rep (500?) on the source site and 5k rep on the destination site (rationale: you need to be truly sure the question belongs there; 2k rep beyond close voting access sounds reasonable for this), you can nominate a question for cross posting. This appears on the destination site as a moderation flag.

If approved, the question appears on the destination's site homepage. The question is shown with the source's favicon and clicking on it brings to the question page on the source site. Thus, only one copy of the question exists; only one site's policies apply; however, users of the destination site can effectively bring additional expertise to the table.

The question will need different tagging on each site it appears on; tagging is up to the user nominating the question for cross posting (rationale: if the question is off topic you'll have trouble tagging).

You could introduce voting for this, but for values of {x} sufficiently high it may be quite hard to find enough users in the intersection of users with enough rep on both sites.

  • 5
    Interesting idea. It probably needs a bit of tweaking to work efficiently, but it sounds like a decent core idea. (Rather than cross-posting it might be nice to be able to move questions between SE sites or just generate pseudo-questions which link to the question on another SE site). If you fancy, post this as a feature request. I'd be happy to support the idea.
    – Noldorin
    Commented Sep 28, 2010 at 18:27
  • This is a great idea. Have you proposed it in a separate thread? This idea is analogous to creating symlinks to files. There should be 1 and only 1 source copy of the question, but there can also be multiple links to it from other SE sites. To initiate the process of creating such "symlink" question, someone (the OP, for example) might propose this on the destination site chat. Such a starter does not require high rep. See also: meta.stackexchange.com/q/355553/578690 Commented Oct 19, 2020 at 16:22

I have no problem with a user posting the same question on multiple sites as long as that is clear. So, I'd say if you do it create links between the questions so that it is completely transparent.

  • So what about from other sites, like searches on google?
    – user344877
    Commented Jan 8, 2017 at 7:01

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