# iOS 11 changed iPhone’s font for MathJax

I updated to iOS 11, and after doing so, the display font for MathJax has changed across the entire interface of my phone. As evidence, here is a screenshot I found laying around with its updated copy:

Before:
After:

Let's define three partitions $P,Q,R$ on $[a,c]$, $[a,b]$, $[b,c]$ respectively:

$$P=\{x_0,x_1,...,x_k,...,x_n\}$$ $$Q=\{x_0,x_1,...,x_k\}$$ $$R=\{x_k,...,x_n\}$$

where $x_0=a,x_k=b,x_n=c$

As the function $f$ is integrable on both $[a,b]$ and $[b,c]$, for any $\epsilon/2>0$ there is a $\delta>0$ such that

$$\left| S(Q,f)-\int_a^bf(x)dx\right|<\epsilon/2$$

I’m a very font-sensitive individual1, and this is one I thoroughly despise (except for the new Q, which I actually prefer over the old one, which always seemed deformed to me).

Is there any way at all that I can change this?

1: Down with Calibri, Arial and Comic Sans! Vivan Baskerville and Didot!

Edit: After reading through MathJax.org, I believe the “old” font was “SVG” while the “new” font is “HTML-CSS.”

• Is there any way at all that I can change this? Not the answer you're looking for, but I've heard of this technique called squinting :) – rschwieb Sep 21 '17 at 12:31
• Solution: Switch to Android. – Asaf Karagila Sep 23 '17 at 21:11
• @rschwieb This actually made me laugh out loud! – Chase Ryan Taylor Sep 23 '17 at 21:14
• @AsafKaragila Same with your comment too ^ – Chase Ryan Taylor Sep 23 '17 at 21:14
• I guess (ios-app) tag or (mobile-web) tag (or even both) might be applicable here. – Martin Sleziak Sep 24 '17 at 5:29

MathJax's HTML-CSS output tries to use locally installed fonts, when possible, and it looks for two local fonts: the MathJax TeX fonts, and the STIX fonts. If neither is found, then web-based fonts are used (usually the MathJax TeX fonts).

In your case, your earlier image shows the MathJax TeX fonts, so that is using the MathJax TeX web fonts. The second image is using the STIX fonts, so it looks like Apple has included the STIX fonts in the latest iOS (they already include them in the desktop Mac OS). Since MathJax looks for those and uses them in preference to the web fonts, that is why the look has changed.

There are several possible work-arounds. First, if you are writing your own web pages, you could configure MathJax to no look for the local STIX fonts. But if you are just viewing StackExchange sites with MathJax enabled, you can't change the configuration. But you can select a different output renderer, as GEdgar suggests. In iOS, in order to activate the menu, you must double-click-and-hold (double click, but keep your finger pressed on the second click for a few seconds before letting go) on any typeset mathematics. That should call up the menu. it is not always easy to do, but with some practice, you can do it.

The CommonHTML and SVG output formats will not use a locally installed STIX font, so you should get the MathJax TeX fonts in those cases.

• Sorry to revive this old question, but the double-click-and-hold thing does not seem to work on the “official” SE app (only browsers). Do you know if there is a workaround, or a way to modify MathJax options from within the app? – giobrach Jan 13 '18 at 20:18

I don't view this on my smartphone. But on my computer, I can choose

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• Wow, I didn't realize that was available! – rschwieb Sep 21 '17 at 12:31
• Incredible! I always preferred the font on mobile – Chase Ryan Taylor Sep 21 '17 at 12:32