Does Stack Exchange or MathOverflow own my posts? Can I reuse my posts elsewhere? Do I need to cite MathOverflow if I want to reuse my posts elsewhere?


2 Answers 2


You own all of your posts! You retain full copyrights and you can do anything you please with them.

However, by posting on MathOverflow, you release your content under the terms of the Creative Commons Attribution-ShareAlike 4.0 (CC BY-SA 4.0) license. This license allows MathOverflow, Stack Exchange and others to use your content under specific terms. This is not an exclusive license. As the copyright owner, you may release your content to anyone under any terms you please, though such waivers do not revoke the CC BY-SA 4.0 license that you previously agreed to.

  • $\begingroup$ I believe this is incorrect -- see my answer to this question. $\endgroup$ Nov 13, 2013 at 12:06
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    $\begingroup$ My answer below was incorrect and the TOS have changed, but I still believe that this answer is not fully correct, as it omits some restrictions. See my new question meta.mathoverflow.net/questions/1212/…. In particular, (1) there are additional restrictions with respect to CC-BY-SA (2) no specific version of the CC-BY-SA is mentioned in the TOS. The TOS themselves contain links to at least two different versions of CC-BY-SA. (3) the author cannot waive the additional restrictions by relicensing, since they are mandated by Stack Exchange. $\endgroup$ Nov 27, 2013 at 11:01
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    $\begingroup$ As pointed out in another answer this is no longer the case: the license is now CC BY-SA 4.0. $\endgroup$
    – David Roberts Mod
    Oct 13, 2019 at 20:27
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    $\begingroup$ @François G. Dorais: What's the status of old content that was contributed by an author under CC BY-SA 3: Is it still under CC BY-SA 3 license or is it now under CC BY-SA 4 license? $\endgroup$
    – tj_
    Oct 15, 2019 at 5:59
  • $\begingroup$ @tj_ I am certainly no expert, so take everything I say with a grain of salt, but presumably SE could just share your content under the 4.0 license and give proper attribution(which your name etc is attached to all your posts so that is already done). I believe that 3.0 has a "can share under compatible licenses"/later version clause $\endgroup$
    – user35370
    Oct 16, 2019 at 13:25
  • $\begingroup$ @tj_ The old content is still licensed under CC BY-SA 3.0. See the official post Creative Commons Licensing UI and Data Updates on Meta SE for full details. $\endgroup$ Mar 19, 2023 at 14:01

EDIT: what is written in this answer does not apply anymore as the TOS have been changed.

EDIT: as @FrançoisG.Dorais and @ScottMorrison point out in the comment, my interpretation here below is probably wrong, too. What is true is that, with the current TOS, if you re-use your own content elsewhere, you have to link to MO as the original source of it.

@FrançoisG.Dorais 's answer is incorrect, at least under a reasonable interpretation of the Stack Exchange terms of service; see here for more detail.

Apparently, by posting content, you restrict everybody (including yourself) to use the contributions only under the CC BY-SA license.

In particular, you cannot use that material in a paper or a book, unless it's licensed as CC BY-SA itself. Given the current state of affairs in academic publishing, good luck getting your publisher to agree to that.

At the same time, Stack Exchange and everyone else in the world has the same rights, so after you post on MO you don't "own" your writing more than Stack Exchange, or I, or anyone else in the world does.

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    $\begingroup$ Frederico, I believe you may be misinterpreting the consequences of this interpretation of the TOS. Since this interpretation contradicts item 7b of the CC BY-SA license, it might invalidate the licensing agreement itself. $\endgroup$ Nov 13, 2013 at 13:49
  • $\begingroup$ @FrançoisG.Dorais I see. So your interpretation is that SE's terms of service are inconsistent and hence invalid? (note: I am not a lawyer, so I might well be mis-interpreting everything) $\endgroup$ Nov 13, 2013 at 14:06
  • $\begingroup$ The most reasonable thing would be to ask a stackexchange officer to give an authorative answer. $\endgroup$
    – Gil Kalai
    Nov 13, 2013 at 16:02
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    $\begingroup$ They say they are working on it: meta.stackexchange.com/questions/203209/… $\endgroup$ Nov 13, 2013 at 16:06
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    $\begingroup$ @FedericoPoloni, also, I don't see anything in the current (generally agreed to be broken) terms of service that say you are restricted to using your contributions under the CC BY-SA license, but merely that when you use your own contributions, you will provide attribution per the CC BY-SA license rules. These are rather different things, and in particular according to the current wording you could certainly use that material in a paper or book, as long as you cited the original appearance on MO. $\endgroup$ Nov 14, 2013 at 4:24
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    $\begingroup$ Frederico, that part of the TOS has been reworded and it now explicitly states the exception that you can do anything you want with your own contributed content. $\endgroup$ Nov 27, 2013 at 0:22
  • $\begingroup$ @FrançoisG.Dorais Thanks for letting me know of the change - I've seen the new TOS and I am satisfied with the changes made. Should I delete this answer outright or just stick an edit on top of it? $\endgroup$ Nov 27, 2013 at 8:27

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