There is this extremely handy feature - you can ping any user participating in a comment discussion with @. In my recent question A "prequestion" about meromorphic representations of algebraic groups I encountered a need to do a similar thing more generally for a user not appearing anywhere on the page, and not from a comment. Specifically, in a comment before we discussed a possibility to ask this question, and now I want to notify him that I did it. In the question, I tried to do it by prepending the username with @ as in comments, but I have no idea whether this will work. Is this documented somewhere?

As pointed out by Emil Jeřábek, there is a meta question discussing the comment notification system, but I could not find there anything about notifying a user not from comments but from questions or answers.

  • $\begingroup$ See meta.mathoverflow.net/q/541 . $\endgroup$ Feb 4, 2017 at 9:29
  • $\begingroup$ @Emil So it does not work? Sorry I cannot quite conclude this from the question and answer that you linked. There, limitations of pinging from comments are discussed, but I could not find anything about pinging from anywhere except comments. $\endgroup$ Feb 4, 2017 at 9:35
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    $\begingroup$ It doesn't work from questions or answers, only from comments. I thought this was also stated there somewhere. $\endgroup$ Feb 4, 2017 at 10:02
  • $\begingroup$ @Emil Still could not find it. The page you linked to also contains a link to a SE meta question, where pinging from comments are discussed in much detail, but also there I could not find any mention of impossibility to do it from questions and answers. In any case I think it would be convenient to be able to do it, and there are examples when it is (almost) necessary. $\endgroup$ Feb 4, 2017 at 16:39
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    $\begingroup$ The closest I was able to find to a post explicitly stating that @pings from posts do not work was this: Can I ping any user I want to take a look at my question? But even if there is no official documentation, I guess several users can confirm from their experience with SE that such notifications do not appear. $\endgroup$ Feb 5, 2017 at 9:24
  • $\begingroup$ @MartinSleziak Thanks, this is what I needed - also in the sense that now I understand why there is no such feature: to avoid too much vanity pinging. I believe this makes an adequate answer, so if you feel like posting it please go ahead. Otherwise I can do it myself. $\endgroup$ Feb 5, 2017 at 9:30
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    $\begingroup$ Possible duplicate of How do I use the comment notification system? $\endgroup$
    – Stefan Kohl Mod
    Feb 6, 2017 at 17:11
  • $\begingroup$ @მამუკაჯიბლაძე I have added one more paragraph to my answer - I'd say that my answer addressed your question as (support) rather than (feature-request). But judging from your previous comment, you have probably abandoned the idea of requesting this new feature - in which case the new paragraph is probably not that relevant. $\endgroup$ Feb 10, 2017 at 6:13
  • $\begingroup$ This question is also tangentially related: How to contact a MathOverflow user? $\endgroup$ Jan 31, 2022 at 5:00

1 Answer 1


I was not able to find some official documentation explicitly stating that @pings from posts do not work - the closest post I found was this: Can I ping any user I want to take a look at my question?

However, I believe that several users can confirm from their experience that notification from questions/answers do not work. (Moreover, in the case described by the OP where the username to be pinged does not even occur on the page this could lead to pinging several users having same or similar username - which is probably undesirable.)

If you want to test this, feel free to "ping" me in your question and if you also want to test answer, perhaps you can use Formatting Sandbox.

EDIT: I have now added @მამუკაჯიბლაძე to my answer. You can check for yourself that while you were notified about posting answer, you did not get an additional notification after my edit which included @username.

However, in the situation you described, I think a comment like this would be ok: "@username I have asked a question related to this one (with adding link and perhaps some more details on how the questions are related). I would be grateful if you could have a look at it."

This should definitely not be overused - comments are primarily intended for things related to post where the comment is posted. And it would probably be considered impolite to ping somebody simply because they are expert but had no previous interaction with related questions of yours. In short, you should use your own judgement to decide where is the boundary.

And of course, if you stumble upon the user in , you can ask there. If this particular user frequents chat, you can even invite them to a chat room. It will create notification and the user can decide for themselves whether or not to accept it. (Again the caveat that this should not be overused.)

I will add - perhaps as a piece of MO history trivia - that there used to be tags and . They are mentioned in this answer and in the comments you can find links to some related discussions. The tag have since been removed.

Of course, adding the tag did not create notification, but it increased the likelihood that a particular user looked at the specific question. And this maybe shows at least a bit that using correct tags can improve the probability that expert in a particular area will look at your question. It seems quite reasonable to assume that many users look mostly at their favorite tags and at the tags from areas they are familiar with.

EDIT 2: Since I see that you have tagged your post as , let me comment also a bit on this. The question whether or not this type of ping works is in my opinion closer to than feature request. If you really want to make this into a feature request, you should definitely spell out more detail. (For example, how would you deal with several users pingable by the string used. For example, writing @Martin would match many users on the site. Even if this feature would be restricted to exact username, duplicate usernames are not disallowed, so there is a possibility that this could ping more than one user.) Another question is whether such a feature question should be posted here or on the main meta, since it would influence the whole SE network. But I guess from your comment that you are probably no longer in favor of of implementing this feature. ("Thanks, this is what I needed - also in the sense that now I understand why there is no such feature: to avoid too much vanity pinging.")


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