The hypothetical possibility of MO leaving StackExchange was mentioned here on meta.MO a few years ago and was mentioned again recently. In a comment, Sam Hopkins asked what I think is a good question.

It would be good to know how "seamless" vs. "messy" divorcing from SE would be, from a purely technical point of view. I understand that MO owns its "data," but would the website and software largely continue to work? Would it go down for hours… days…?

In fact, I think it would be useful to spell out some potential non-technical downsides of leaving as well. For example, might it hurt the MO community by decreasing participation, or creating internal conflict as people debate the pros and cons of leaving? The chances of that happening would presumably be reduced if the migration were largely transparent to the end user, but how transparent it would be would depend on the exact mechanics of the transition. Would we retain the same domain name? How similar would the user interface be? In short,

What technical and non-technical disadvantages would an MOexit likely have?

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    $\begingroup$ IANAL, but the way I understand the terms of the agreement, the domain mathoverflow.net belongs to MathOverflow, Inc. Of course, I understand that if the "new MO" would be a part of larger network with several Q&A sites, that might possibly lead to change of the URL to correspond with other sites in the same network. $\endgroup$ Commented Jun 11, 2023 at 13:15
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    $\begingroup$ Maybe there are also some drawbacks regarding 'moderator tools' (in a broad sense), including automatic or even network-wide tools, e.g. tools to deal with different kinds of spam, abusive users, AI-generated content, hacking attempts and other kinds of malicious attacks? I have no insight into this, but perhaps some of our moderators could shed some light as to whether, and if yes, to what extent this would be affected. MO should not remain 'defenseless'. $\endgroup$
    – M.G.
    Commented Jun 11, 2023 at 22:00
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    $\begingroup$ Tentative title change suggestion: MOexit -> MOxit :-) $\endgroup$
    – M.G.
    Commented Jun 12, 2023 at 15:06
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    $\begingroup$ How about the gerundive: MOvendum? $\endgroup$ Commented Jun 13, 2023 at 1:31

4 Answers 4


As the founder of one of the sites on this network, who has put an insane amount of time into building that community of 6000+ users, I want to escape from SE just as much as anyone else, but certainly there's disadvantages. Nothing below should be interpreted as me saying it's a bad idea to exit. It's just my honest opinion.


SE is constantly getting DDoS attacks. A security team helps us deal with those, and helps ensure that our passwords and private data (e.g. the IP addresses from which you accessed the site each time, which can tell hackers your address, your choices of hotels and locations of travel, the family members you visit as long as you view MathOverflow from your phone while there, etc.) are somewhat safe. Having SE-level security will likely not be cheap. Here's a list of security vulnerabilities that were found by non-MO users of SE over the years.

SE currently uses 600,000 web sockets, 3 elasticsearch servers (128GB of RAM each), two redis servers (256GB of RAM each), about 2 SQL servers (768GB of RAM each), 9 web servers (64GB of RAM each), and deals with a transfer of 55 TB of data per month. MO will not need that much, but running and maintaining servers has a cost.

Web development is also a constantly changing occupation. My first website (circa 1996) was done in pure HTML, but now a site like MO can't be maintained without knowledge of a lot of the following things: CSS, Javascript, PHP, React/Angular/Vue, HTML 5, SQL/MongoDB/Firebase, Python, etc. Furthermore, the web development/design team needs to constantly stay up-to-date as security threats change and as browsers change, and as hardware and culture changes (making a site work well on small phones, tablets, etc.).

User participation would drop

Let's look at some of the other success (actually "lack of success") stories for Q/A communities that are not part of the SE network.

  • PhysicsOverflow. Notice the lack of usage, the archaic aesthetics, and the fact that the site looks completely messed up when you try to view it from a phone rather than a desktop. I say this with the utmost respect for the founders of the site, knowing that starting one of the SE sites and getting it through Area51 was the hardest thing I've ever done in my life, and that I'd still probably prefer having gone through what I did versus trying to do everything on my own.

  • Codidact. Notice that nearly no one uses it, including the main "founding face" and popularizer of the community, which is Monica Cellio (until recently when this strike action started, she hadn't posted there for a long time, despite probably being the one with the most vested interest in growing that community). Also be aware that the vast majority of the content there is simply copied and pasted from SE thanks to the creative commons license which allows them to do that. I say this again with the utmost admiration for what the Codidact founders have accomplished and for their vision, which I support enthusiastically (I was in fact one of the early contributors to design elements that are still in place). Another problem with this community is that the main founders (Monica Cellio, ArtOfCode, Mithrandir, Mithical, luap/MEE) have in my opinion too much in common with the people currently running SE: 100% of my conversations with Monica about Codidact have been pleasant, but I have had mostly negative experiences with the other four.

  • TopAnswers. This community is so unknown that I don't even know what to say here, other than the fact that I occasionally see this site mentioned as an alternative to SE, for example here.

  • Materials Science Community Discourse. This is probably the closest to what the MO community would want to do. it's powered largely by Discourse which is also free and open-source like the Q/A engines in PhysicsOverflow and Codidact, but unlike those two, it's much more widely used (and one of the founders is actually Jeff Atwood, who also founded StackOverflow!). However I can already see that the Materials Science Community Discourse website has a big banner saying that it's not supported on my browser (not a problem with SE). Also, it is a "traditional forum" with no voting, comments, or any of the other things that make SO/MO/SE the way it is.

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    $\begingroup$ How many of the "lack of success" stories are cases where a successful site took a nosedive, as opposed to failing to get traction in the first place? $\endgroup$ Commented Jun 11, 2023 at 23:03
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    $\begingroup$ @TimothyChow Codidact was mostly created the last time SE moderators went on "strike", which was in 2019. PhysicsOverflow was created in response to some clashes among members of Physics.SE, I don't know much about Topanswers, and the Materials Science Community Discord was not made in response to a nosedive as far as I know. I just remembered that I wanted to also include Biostars in my original answer. I'd say Codidact was made in response to the biggest nosedive SE ever had (except maybe the current one). We still 4 years later see people on SE with usernames like "Peter supports Monica". $\endgroup$ Commented Jun 11, 2023 at 23:25
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    $\begingroup$ Thanks for the extra information. I realize that I didn't phrase my question clearly. What I meant was, are these examples where there was a thriving site, and then after the site migrated, the new site became a failure? As opposed to sites that were never successful in the first place? MO is currently successful, so my concern is that it may cease to be successful if it migrates, and I'm wondering if there are precedents for this sort of thing. $\endgroup$ Commented Jun 11, 2023 at 23:38
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    $\begingroup$ Perhaps a question such as "What are some examples of thriving sites that have migrated to a new platform, and how successful were they?" would be appropriate and would allow me to write much more (and others that collectively know more than me could probably give far more examples than I can). Maybe the best example of a site that officially migrated from one platform to another, is MathOverflow which migrated from StackExchange 1.0 to StackExchange 2.0. Codidact was an attempt at migrating several SE sites (e.g. EE, Physics, Writing, Judaism, etc.), but it was not "official". $\endgroup$ Commented Jun 12, 2023 at 1:15
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    $\begingroup$ I don't know what you consider "a long time", but Monica posts questions when she has questions, and I see some from a month ago and some from two months ago, and she's very active on meta.codidact.com. In response to @TimothyChow's question, it's a failure to get traction and doesn't have much bearing on the potential impact on MO of migrating platform while retaining its domain. $\endgroup$ Commented Jun 12, 2023 at 8:49
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    $\begingroup$ I think it's worth commenting that æsthetics are very much a personal preference. PhysicsOverflow looks just fine to me. (I literally mean that in the sense of its appearance; I'm in no shape to judge its community.) $\endgroup$
    – LSpice
    Commented Jun 12, 2023 at 19:50

In addition to practical issues around making the move and practical issues around whether the new hosts would do as good a job as SE, there's also the major concern of whether the new hosts would continue to exist at all 5 or 10 years down the road.

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    $\begingroup$ A good point — but this is far from certain for SE either, especially if we take “exist” as “exist, and offer an acceptable service”. So I’d perhaps suggest framing this less as “will the new host still exist in 15 years?”, but rather as “how do the new host’s prospects in 15 years compare to Stack Exchange’s?” $\endgroup$ Commented Jun 13, 2023 at 8:26

Answering directly to your questions:

Would we retain the same domain name?

Yes, because the domain name is property of the Mathoverflow foundation. Source

How similar would the user interface be?

Look for yourself, Codidact is the main alternative at the moment. It is a step down, in my opinion.

might it hurt the MO community by decreasing participation

In part, because you lose those who come from the hot questions sidebar, or those that have already a SE account and are too lazy to create a new account. This is not necessarily a bad thing, though, because we might lose some of the low-quality posts.

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    $\begingroup$ In what ways do you find Codidact to be "a step down"? $\endgroup$ Commented Jun 12, 2023 at 11:39
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    $\begingroup$ @TimothyChow Various minor things that make it seem less polished in general: for instance, it is more cramped, comment threads are less higlighted visually, the tag infobox is less polished, some information such as the license could be less highlighted etc. Nothing major, just a general feeling (and just my personal non-expert opinion). $\endgroup$ Commented Jun 12, 2023 at 13:34
  • $\begingroup$ Hot network questions is a big one, for "exposure" (spreading awareness of work), external but useful contributions (e.g. @NikeDattani's answer), and, it and maybe the opposite, "inspiring" with fancy math. $\endgroup$ Commented Jun 23, 2023 at 7:09

This probably depends on the way how MO would (try to) continue.

  • As a separate site (with its own hosting and infrastructure),
  • or as a part of some network which hosts several sites. (I.e., something similar to Stack Exchange or Codidact).

There are several advantages to being part of the network. (Probably most of them are more-or-less obvious.)

  • MathOverflow, Inc. would have to deal with all technical issues by itself. For comparison, at the moment the only thing related to MO which isn't hosted by SE is the archive of the old tea. It is down at least since January 2020 and in all that time we did not even get any response from the mods whether or not the archive is considered abandoned or whether they plan to revive this at some point. The redirect, i.e., the part which was setup by SE, still works - but it goes to a dead page. (And, as a consequence, the answer to the very first question here on meta is - at the moment - untrue.) I understand that the main site is much more important than an archive with various old discussions - so MO wouldn't simply go silent for several years - but still, I would consider this as a datapoint showing that it is difficult to manage various real-life commitments and devote the time to keeping a big website alive.
  • As a part of a larger network, MO can rely on help of users from other sites. There are things where people without knowledge of research-level mathematics are certainly able to help, too. (To use the local MO terminology, we barbarians can be useful, too.) As a specific example I will mention removing spam - you can find at least some details about the Charcoal project in this answer: What should I do when I see a spam post on MO?
  • Collaborating with multiple sites would mean that the moderators would have the opportunity to ask for advice when they face with various problems. Certainly the MO moderators try to do good job, but naturally - as any human being - occasionally they might make a mistake. I'd expect that in such situations, help from some experience mods of other sites (in the same network - i.e., dealing with the same Q&A software) could be a very useful thing.

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