The title says it all. :-)

In response to the automatic disapproval of the question body:

I tried to edit the chat messages after submitting but couldn't figure out how to do that either. (And I hope that my English grammar, though certainly imperfect, is still within limits).

  • $\begingroup$ This older post (which I also linked in my answer) seems related: MathJax on Chat. $\endgroup$ Commented Dec 9, 2017 at 8:04

2 Answers 2


MathJax in chat

You can find some information on MathJax in chat in the following posts from Mathematics meta:

I have changed the wording in the second bullet point since several users - who probably have better knowledge of these issues than I do - mentioned in the comments that this should not cost additional resources on the server side.

More-or-less the same is explained in this older question on this meta: MathJax on Chat.

I can confirm from my experience in chat that many users use the bookmarklet linked above for this purpose. At the moment, the only room associated with MathOverflow which is really active is Homotopy Theory. Since I see that one of the above links is explicitly mentioned in the room topic, I suppose this bookmarklet (or some other similar script) is used in chat also by MO users.

Editing messages in chat

About your second question:

I tried to edit the chat messages after submitting but couldn't figure out how to do that either.

You have a short grace period when messages can still be edited. But you cannot edit older messages. (Moderators are exception to this rule.)

Quote from the chat FAQ:

If you make a mistake when entering a message, press the up arrow to edit your last message ... or press esc to cancel editing. You have 120 seconds to edit your messages. All edited messages have a small edit indicator.

The faq for chat contain several things which might be useful to know if somebody plans to use chat regularly.

Whether a chat message is edited or not, after you move your cursor on the message you can see a little downward arrow on the left. After clicking on this arrow, one of the options you can choose there is history. There you can see "the source" of the message - this is useful especially if you do not know how to make some kind of formatting but you see message by other user that contains what you want. For example, for this message the history looks like this. (It also illustrates that the moderators are exempt from rather short time limit when it is possible to edit chat messages.) This might be useful for users who is new to chat to learn how a formatting works. But also if you want to copy text (including the formatting) of some of your previous messages. (For example, if the message are no longer editable, but you still want to post also post a new version where the typos are corrected.)

  • 3
    $\begingroup$ Thanks for the clear and comprehensive answer! Yeah, the system resources are limited, but so is human time and patience, so we always have to find some trade-off that doesn't exhaust either one if we want a smooth operation of both components :-). So far what you suggested satisfies my needs, so the case is closed as far as I'm concerned. Upvoting and accepting. $\endgroup$
    – fedja
    Commented Dec 10, 2017 at 0:43
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    $\begingroup$ Personally, I am not convinced by this explanation. Mathjax renders client-side, so when they write "big strain on the system" they surely mean on the client's system, not on their server. And rendering a few formulas can't be too much of a strain --- there are hundreds of them in some Q&A pages. And Mathjax can re-render selectively parts of a page. Maybe they really meant "we do not wish to invest the resources to implement it"? $\endgroup$ Commented Dec 13, 2017 at 15:07
  • $\begingroup$ @FedericoPoloni Maybe my wording was not ideal, but what I wrote is based on how I understood this: "This request was discussed by the team on April 9th, 2014. The potential rendering cost would be such that it would need to be a per-room and per-user option; this would then create a situation where users would potentially never be sure how their messages would look to other readers - in other words, little better than the user-script solution currently available." $\endgroup$ Commented Dec 13, 2017 at 15:10
  • $\begingroup$ Just to make it absolutely clear, the wording "it would create too big strain on the system" is mine. It is based on my understanding of what I read elsewhere. (See the links in the answer.) Since I do not now much about programming websites, it is entirely plausible that I might have misunderstood something. $\endgroup$ Commented Dec 13, 2017 at 15:16
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    $\begingroup$ I'd like to second Federico's comment from 4 years ago. If mathjax is installed as it is on Mathoverflow pages, there is essentially no cost to the server. All that happens is that the server tells our browsers to download and run a javascript from another site. It is our browsers and not the server that does the download and our browsers that render and display any tex that appears on the page. So the server does almost nothing. $\endgroup$ Commented Dec 21, 2017 at 13:04
  • $\begingroup$ @BrendanMcKay To avoid confusion of people reading your comment (including me), which comment are you referring to? You are referring to "Federico's comment" - the comment by Federico Poloni was posted about a week ago (timestamp is 2017-12-13) - and you are also mention comments from 4 years ago, which suggests you mean a completely different comment. $\endgroup$ Commented Dec 21, 2017 at 13:28
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    $\begingroup$ @MartinSleziak Sorry. I was referring to the comment of Federico on Dec 13 (somehow I read it as Dec 2013; shows how much attention I was paying). $\endgroup$ Commented Dec 22, 2017 at 2:31

User script ChatJax++ (which requires SOUP, a collection of useful fixes for the SE platform) has been working well for me.

Both user scripts have been developed by Ilmari Karonen.


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