As everyone knows, we get a fair number of questions on this site that are not research level, but would be appropriate for http://math.stackexchange.com. As a frequent Math.SE user, I have an interest in seeing that they get there (particularly because sometimes I want to answer them!).

We have a "migrate to Math.SE" closure reason, under "This question belongs on another site". However, in order for a question to be migrated, we need a majority (?) of the close voters to choose this reason. Unfortunately, what usually happens is that a majority of close voters will choose one of the following two close reasons, which are usually also applicable:

  • "This question does not appear to be about research level mathematics within the scope defined in the help center"

  • "MathOverflow is for mathematicians to ask each other questions about their research. See Math.StackExchange to ask general questions in mathematics."

Both of those are true statements about the typical migration-worthy question, but choosing either of those close reasons does not cause automatic migration.

So the usual result is a question that is simply closed here, and the user either reposts on Math.SE, or gives up altogether. Either way we don't get the benefits of migration.

Maybe part of the solution is just educating 3K users about the benefits of migration and how to achieve it, but it might also be possible to reword the close reasons to help users realize that the migration option should be used when possible. The "See Math.SE to ask general questions" close reason seems particularly unhelpful since I think it actively leads people away from the migrate option.

A shining example (as of this writing) is https://mathoverflow.net/questions/209798/is-there-a-bicontinuous-bijection-from-the-reals-to-the-continuous-functions-ove. There is a +4 comment saying "This is a good question, but take it to Math.SE". It was closed with the "See Math.SE to ask general questions" reason (my vote for migration fell in the minority), so migration did not happen. I know an answer to the question and could post it right now, but I can't post it here (as the question is closed) and I can't post it on Math.SE (as the question doesn't exist there yet).

We could flag a moderator to migrate it manually, but that is a pain for the moderator. Moreover, by the time it happens, the asker may well have already reposted on Math.SE. Then there is a duplicate on Math.SE, which is a pain for their users/moderators to clean up.

How can we improve this?

  • 1
    $\begingroup$ Sometimes migration even doesn't work if a majority of close voters choose the migration option, and the question is just closed -- I remember to have read that this may be related to tags which do not exist on the destination site(?) $\endgroup$
    – Stefan Kohl Mod
    Commented Jun 21, 2015 at 9:25
  • 1
    $\begingroup$ "Either way we don't get the benefits of migration." Which are? $\endgroup$
    – user9072
    Commented Jun 21, 2015 at 10:46
  • $\begingroup$ @StefanKohl indeed, if a question has no tag that exists on the target site (not even as synonym or intrinsic tag) the migration is rejected. It is easy to avoid this for migrations to Mathematics as all MO top-level tags should exist as synonyms on Mathematics. $\endgroup$
    – user9072
    Commented Jun 21, 2015 at 11:03
  • 1
    $\begingroup$ I should say that the closing system is a bit confusing (at least it first was to me), in off-topic you have to choose between 1) This question does not appear to be about research level mathematics within the scope defined in the help center. 2) MathOverflow is for mathematicians to ask each other questions about their research. See Math.StackExchange to ask general questions in mathematics. 3) This question belongs on another site in the Stack Exchange network. (...) $\endgroup$
    – YCor
    Commented Jun 23, 2015 at 0:16
  • $\begingroup$ (...) Maybe as non-English speaker I first understood 3) as "the question exists on MathSE/..." while it means "I'm voting to migrate the post to MathSE". Also strangely, if the question is closed then it's reversible (it can be reopened) while if migrated it sounds not easy to cancel. And the difference between 1) and 2) still sounds unclear to me: if a question is not of research level then both 1,2 apply and 3 is also an option. $\endgroup$
    – YCor
    Commented Jun 23, 2015 at 0:18
  • $\begingroup$ @YCor I agree that the phrasing for the path to migration is not the most intuitive. However, I do not see anything strange about closure being reversible easily but migration being reversible only in somewhat complicated ways. Indeed, a point of putting a question "on hold" is to give OP the possibility to improve the question to make it on-topic (this will not always be possible, but still it is the idea). By contrast, migration means that the question is (very) good as is for another site (but not this one). And, sent there, it is theirs; one cannot take back a gift either. $\endgroup$
    – user9072
    Commented Jun 23, 2015 at 8:50
  • $\begingroup$ For the other point: indeed, 2 is a special case of 1. That 1 is present at all has also historical reasons (personally I would prefer it was not there anymore in this form). Recall originally there was only a general "off-topic" and it was common to explain in a comment what specifically was the issue. Now, we can customize close reasons to save the effort of typing out the comment for the most common case(s) frequently, whence 2. More exceptional cases can be dealt with via the "other" reason (making the reason explicit). @YCor $\endgroup$
    – user9072
    Commented Jun 23, 2015 at 9:02
  • $\begingroup$ Any plans to follow up? My question was not rhetorical. $\endgroup$
    – user9072
    Commented Jun 24, 2015 at 11:19
  • $\begingroup$ @quid I'm assuming you're referring to your question to Nate, about the benefits of migration to us (where I'm supposing 'us' might include the poster as well). $\endgroup$
    – Todd Trimble Mod
    Commented Jun 27, 2015 at 11:48
  • $\begingroup$ @quid: Sorry that I lost track of this. I think the main benefits of migration are to other MO users who found the question interesting, and maybe want to answer it. With migration, they can easily find the MSE version of the question (since the question continues to exist on MO for a time, with a link to MSE) and immediately answer it... $\endgroup$ Commented Jul 31, 2015 at 13:54
  • $\begingroup$ @quid Without migration, they have to wait around to see if the OP will decide to repost to MSE. Then they have to try to find the MSE question (which may now have a different title, etc). It's a drag. There is a slight benefit to the OP who gets the question to MSE without delay, and without having to copy-and-paste, but this is not quite as significant in my mind. $\endgroup$ Commented Jul 31, 2015 at 13:56
  • $\begingroup$ Thanks for the reply. The point that with migration there is at any point in time an open version of the question is a valid advantage. From the askers perspective (as I explained) to me it is a quite mixed bag. For the MO users that might want to answer I can see that it could be convenient. My main concern regarding migrations is though that what sounds quite alright in theory does not work so well in practice. Having 10k+ on Mathematics you can check easily what happens to migrated questions from MO there. Often not much (good). $\endgroup$
    – user9072
    Commented Jul 31, 2015 at 15:03

2 Answers 2


While the specific example could have been a solid migration, I disagree that anything should be "improved" to have more migrations. If anything, still less migrations should happen.

First, some data:

  • 18 percent of the migrations to Mathematics got rejected (in the last 90 days, this is the number from math.se).

  • 17 percent of the questions on Mathematics get closed (this is 14days number, the longer one fail to open for me).

Thus, the questions migrated do not fare better, maybe even slightly worse (but there might be some artifacts in the data), than the normal questions. It seems we do not do a good job at selecting questions.

Part of the reason might be that in certain aspects Mathematics has stricter standards on questions than MO. This is what Joonas Ilmavirta alludes to with lack of details.

I do not want to discuss the merits of the standards on Mathematics here. For this discussion, they are what they are and many users there vote according to them and we need to be aware of the standards on Mathematics when we send questions there. (Otherwise they are just returned to sender.)

And, as Asaf Karagila mentioned already a closure of a migrated questions is quite inconvenient to deal with. Basically, if a question is migrate it must definitely work "as is" on the target site. The usual "on-hold, improve, reopen" gets broken by migrations on the target site.

More generally, I feel migration is often a disservice to the OP.

  • It can be confusing (especially for new users).

  • They might well end up with a locked question on Mathematics, where they should improve the question.

  • They might get substantially less visibility on Mathematics, as the question is inserted in the "new"-queue with the date it was originally asked and as the question might end up poorly tagged.

What do they get in return? Not having to do a copy-paste. Anything else?

Pointing out the other site and just closing (in my opinion) is almost always the better option, which is one reason why that close reason exists in the first place.

  • 2
    $\begingroup$ Good explanations! -- I also feel migration is not much service to the OP or to the target site. I think migration is rather beneficial in a certain sense to the source site if a question already has answers. -- Other than if an off-topic question is merely closed, the answers to a migrated question get deleted; this has at least two effects -- firstly, people don't get the impression that they could get such question answered on the source site, and secondly, the migration stub gets autodeleted after some days -- whereas a closed question with answers is not. (I'm not saying this is good!) $\endgroup$
    – Stefan Kohl Mod
    Commented Jun 21, 2015 at 13:53
  • $\begingroup$ Interesting data! Is it easy to access or generate it somehow? It would also be interesting to see what kinds of migrated questions get closed at MO. $\endgroup$ Commented Jun 21, 2015 at 17:37
  • 4
    $\begingroup$ "the question is inserted in the "new"-queue with the date it was originally asked" <-- this is not a very good design feature IMHO. $\endgroup$
    – David Roberts Mod
    Commented Jun 21, 2015 at 23:28
  • 2
    $\begingroup$ @JoonasIlmavirta 10k+ users have access to this data under "tools." $\endgroup$
    – user9072
    Commented Jun 22, 2015 at 0:23
  • 1
    $\begingroup$ @DavidRoberts the migrated post retains somewhat inevitably its history from the original site on the new site and thus its original date of creation. It would also be weird to have a question "created" on June 21st with answers dating from June 19th for instance. The way things are it fits somewhat naturally in, if one would want to do it differently I think one would have to do a lot of special-casing for that corner-case migrated questions. $\endgroup$
    – user9072
    Commented Jun 22, 2015 at 0:29
  • 3
    $\begingroup$ @quid it could be bumped by the community-user, it doesn't have to come into the stream as a new question. $\endgroup$
    – David Roberts Mod
    Commented Jun 22, 2015 at 1:49
  • $\begingroup$ @DavidRoberts The "new"-queue is created according to the time "asked." Nothing of which I know has an effect on the "asked" time. In particular, bumps by the community user have no effect on this, and thus the position of the question in the "new"-queue. Presumably you are thinking about the "active"-queue. $\endgroup$
    – user9072
    Commented Jun 22, 2015 at 10:11
  • $\begingroup$ Yes, I'm thinking of the active view. $\endgroup$
    – David Roberts Mod
    Commented Jun 22, 2015 at 11:59
  • $\begingroup$ @DavidRoberts I do not get your point then. In the "active"-queue the question is inserted at the top anyway. $\endgroup$
    – user9072
    Commented Jun 22, 2015 at 12:09
  • 3
    $\begingroup$ @quid well then I can withdraw my complaint! :-) I see I didn't read the original quote I cut and pasted very carefully... $\endgroup$
    – David Roberts Mod
    Commented Jun 22, 2015 at 23:53

Thanks for bringing this up! I agree that there are many migration-worthy questions that are closed in a suboptimal way.

As I was one of those who voted to close your example question "for wrong reasons"1, let me tell how I try to use the different off-topic closure reasons:

  • Generally off-topic: I only choose this option if the question should not be asked at MO or MSE, even with major improvements.
  • Off-topic, see MSE: I choose this option if the question is inappropriate for MO but would probably be ok at MSE after improvements. If the question is interesting but lacks details or the OP's own ideas, it is in danger of being received with hostility at MSE. The OP is more likely to get a good answer if they meditate for a while, improve their question and then post it at MSE. To make this idea work, I should of course tell the OP how to improve the question. I must admit being too lazy to give such instructions every time, but I try to do it often.
  • Migration to MSE: I choose this option if the question is inappropriate for MO but would probably be well received at MSE as it is.

The boundaries between the three cases are not sharp. With the example question I hesitated between the last two options on my list and ended up choosing the middle one. If I were to choose now, I would probably pick the third one instead. I don't know if my policy is a good one (= serves its purpose), so I'm open to suggestions.

I agree that the middle option is often quite unhelpful, but it can become helpful if we also advice the OP to improve the question or look at MSE help pages before posting there. I might even suggest adding a link to MSE help pages about asking a good question into the closure reason text.

1 Despite this choice of words, I'm not offended. I'm glad this was brought up.

  • 12
    $\begingroup$ It should be pointed that if a question is migrated and gets closed on MSE, then it is locked there, and the copy here gets closed as off topic anyway. Which is why the distinction between options (2) and (3) is important. If in its current form it will be closed on MSE, it shouldn't be migrated. Or, to quote the golden rule of migrations, "Don't migrate crap". $\endgroup$
    – Asaf Karagila Mod
    Commented Jun 21, 2015 at 9:03

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