This question uses $\mathrm{CO}_2$ formatting in the title (Latex I believe MathJax).

Picture in case someone edits it out: enter image description here

Personally I find it superfluous and annoying - you see the title being constructed (4 'jumps'!) in the browser when you visit any page displaying that title.

But in running texts (on other SE sites as well) chemical formulas are often written this way, because if offers the possibility of subscripts.

Should we edit and remove this kind of formatting in titles?

Here is a meta.SE question about backticks in the title where the answer states Markdown isn't run on the title whatsoever. Any special characters get converted to their entities. This suggests that any formatting should be avoided.

  • $\begingroup$ Note that the $...$ and $$...$$ is mathjax, not markdown. Mathjax gets parsed client side by a javascript library included in the page. They do render in titles except on mobile, where you'll see the raw mathjax markup. $\endgroup$
    – casey
    Commented Sep 1, 2015 at 13:43
  • $\begingroup$ @casey That would be an argument for removing the formatting $\endgroup$
    – Jan Doggen
    Commented Sep 1, 2015 at 14:47
  • $\begingroup$ To note: this is not a major issue, but if a question title contains mathjax, it will not be shown in the Hot Network Questions. Other than that, I'm not aware of any issues -- simply personal preference. $\endgroup$
    – hichris123 Mod
    Commented Sep 3, 2015 at 1:32

2 Answers 2


The $...$ and $$...$$ are not markdown but rather mathjax, which is parsed clientside by a javascript library when you load the page. This will render in titles and comments except on mobile, which only runs mathjax on post content.

For simple to recognize content, I think mathjax is fine in titles. I might prefer $\ce{CO2}$ ($\ce{CO2}$) over $\mathrm{CO}_2$ ($\mathrm{CO}_2$) and definitely over $CO_2$ ($CO_2$).

The downside to mathjax in titles is that they are not universally rendered (e.g. on the Android SE app) and they are stripped from google:

enter image description here

But this doesn't really pose problems in searching unless your title is completely mathjax and there is not much going on in your post. This might be an issue for the math stack exchanges, but not really for us.

There are various debates on the use of unicode vs mathjax for subscript/superscripts in titles, and that comes down to preference. I wouldn't go around editing one to the other.


  • $\begingroup$ If mhchem is supported here that should be added to the list at meta.stackexchange.com/a/216607/189029 $\endgroup$
    – Jan Doggen
    Commented Sep 1, 2015 at 19:56
  • $\begingroup$ @JanDoggen feel free to edit that post to include it. It isn't an authoritative list. The easiest way to check is to just try to use them in a post (you don't have to actually submit the post, they'll render in the preview if they are turned on) $\endgroup$
    – casey
    Commented Sep 1, 2015 at 19:58
  • 1
    $\begingroup$ An additional (minor) limitation is that such questions can not end up in the Hot Network Questions list, as titles containing mathjax are filtered out since they are not rendered on all SE sites. $\endgroup$
    – plannapus
    Commented Sep 2, 2015 at 6:23

(Answering my own question)

After further investigation I found this question on meta.SE:

Which Stack Exchange sites use MathJax?.

Earth Science is mentioned there.

A quick check with the standard browser and with FireFox on an Android device shows that the title is rendered correctly.

So since MathJax is fully supported and works, it should be preserved, however ugly I find it.

  • $\begingroup$ Yes, we support MathJax (see this, this and this). MathJax only renders on sites enabled by SE to include the necessary javascript library. $\endgroup$
    – casey
    Commented Sep 1, 2015 at 19:34

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