There have been some discussions of this topic on other metas, and it seemed to me that the consensus is to avoid MathJax in titles if possible, for various reasons like improving the look of the posts in HNQ and other places where MathJax is not enabled, as well as avoiding the interference of MathJax handling of mouse events with behavior of hypelinks.

According to this, I've recently edited this question (see revision 7) to convert $HeH^+$ to HeH⁺. In an hour, a moderator edited the post, (among other changes) bringing MathJax markup back with $\text{HeH}^⁺$ and $\text{H}_2$ items.

What is the position of Physics.SE on this? In the context of question titles, is $\text{HeH}^⁺$ and $\text{H}_2$ preferable to HeH⁺ and H₂? Do we ever want to avoid MathJax in the titles?

  • 2
    $\begingroup$ Note that it was the case for a while (and may be still) that having $ characters in the title simply excludes a post from HNQ, since such titles display differently on sites around the network depending on whether MathJax is enabled or not. One reason we got the ability to remove questions from HNQ manually was to stop knowledgeable users from adding ${}$ to titles, which would remove a question from HNQ by stealth. $\endgroup$
    – rob Mod
    Commented Feb 23, 2020 at 13:49
  • $\begingroup$ @rob Yes, questions whose titles contain MathJax markup are excluded from the HNQ. See meta.stackexchange.com/a/61343/334566 which was last updated 2019 Nov 21. $\endgroup$
    – PM 2Ring
    Commented Feb 24, 2020 at 1:03

2 Answers 2


I would argue that

MathJax in titles should be kept to the minimum required, and as readable as possible, but if it is integral to writing a good title for the question then it should very much stay there.

In other words, if a title requires explicit mathematics, then those explicit mathematics should stay there. Our site has a bunch of questions that are intrinsically about a very technical subject matter, and attempting to dance around the math by trying to describe it with words often results in a bland pulp of a title that doesn't say anything at all. This should be avoided.

However, that said, MathJax in titles does come with a cost.

  • It comes with the cost that it cannot be displayed on other SE sites in the HNQ sidebar, so it wont' be shown there. This is a red herring -- we're not here to optimize for HNQ.

  • The true cost is that it does not render correctly in external search engines. As a reminder, this is what the split for this site's traffic sources looks like:

    The search-engine pie slice consists of about 96% Google, and about 1% each for Bing, DuckDuckGo, Ecosia, with some other tiny sources. The referred traffic is about 35% internal PSE traffic, and the rest of the reported sites are all from other SE sites (read: HNQ).

    Having lots of unreadable MathJax in the title makes it hard to parse in the linking source for 90% of our traffic. This should not be dismissed.

So, those two criteria are in some tension. Since disregarding the first makes for useless titles, however, we should keep the MathJax when it is necessary, but due consideration should be made so that the title is as readable as possible when seen in un-MathJax-ed plain-text form.

The question you linked to is a good example:

  • $HeH^+$ ($HeH^+$) is bad MathJax, and should not be used at all. Element names should be typeset in upright script, not italics.
  • HeH⁺ (HeH⁺), with plain unicode, is acceptable, but its formatting will disagree with the other titles on the PSE front page (and other pages that list titles) in a way that's likely to either be noticeable or to be jarring even if not noticed. One should also keep in mind that unicode display is sometimes inconsistent: even if it displays correctly on your device, there's no guarantee that it will show up as you intended on other devices.
  • $\text{HeH}^+$ ($\text{HeH}^+$) is correct MathJax, but it is clunky and makes it hard to read when rendered in plaintext.
  • Instead, I would argue that the correct typesetting to use here is HeH$^+$ (HeH$^+$):
    • it is semantically correct and will render correctly when MathJax is turned on,
    • it is much more readable when seen in plain text,
    • the text will render in the same font as the rest of the title, so it will harmonize better with its surroundings.

Finally, for full clarity: displayed equations (i.e. the use of double dollar signs, $$ maths $$, which take up a separate line) is absolutely not appropriate in a question title. Displayed maths take up multiple lines in every place where titles are listed, and doing so amounts to an abusive occupation of space, to the detriment to the other questions in the listing.


Yes, mathjax in titles is allowed and even encouraged for better readability/clarity. The main priority is to optimize the user experience for Phys.SE. The HNQ is separate from the Phys.SE and has lower priority. The HNQ is only relevant for a day or two, while the Phys.SE repository is permanent.


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