tl;dr For any secure (https) webpage with URLs in its source code to Google fonts or MathJax, those URLs must also be secure (https); otherwise, the fonts, $\LaTeX{}$, etc. won’t render.

It’s been nearly a year since I last posted. One of my resolutions this year (my dissertation year!) is to write more, including on this blog. Ideally I’d write about semantics, but for now, just to get back into the swing of things, I’ll be happy to write about anything. To that end, here’s a post.

I just upgraded pandoc yesterday and decided to rebuild my blog to see if any changes would occur. (I write my blog in markdown and then convert to html using pandoc, so basically I reconverted all my posts markdown -> html.) Aside from the copyright changing from “2012–2014” to “2012–2015”, there was only one subtle, but substantial change, and that has to do with MathJax.

MathJax is “an open source JavaScript display engine for mathematics that works in all browsers”. For example, it renders the html code $$f(x) = x^2 + 4x - 3$$ into $f(x) = x^2 + 4x - 3$. The stuff between $$...$$ is $\LaTeX{}$ code, and $$...$$ are the delimiters that MathJax looks out for. But actually, since I write my blog in markdown, I delimit $\LaTeX{}$ code using $...$ (just like in $\LaTeX{}$ itself) since that’s what pandoc looks out for. In other words:

1. Write in markdown: $f(x) = x^2 + 4x - 3$
2. Markdown becomes html (via pandoc): $$f(x) = x^2 + 4x -3$$
3. Html becomes pretty (via mathjax): $f(x) = x^2 + 4x -3$

MathJax is run as a script within the html source code. All you need is something like this, which links to some MathJax JavaScript:

<script src="http://cdn.mathjax.org/mathjax/..." type="text/javascript"></script>


(The full MathJax source URL is here.)

The pandoc option --mathjax is supposed to automagically add the source URL, and it did, until the recent pandoc update. After the update, I noticed that the http: part was completely missing. Apparently, this isn’t really a bug; it was removed for principled reasons. The solution, I thought, was simply to change from using --mathjax to explicitly using

--mathjax="http://cdn.mathjax.org/mathjax/..."


I tried that, and it worked! At least, on my local copy of the blog (file:///home/brian/blog/...). It did not work when I pushed the changes to github (http://brianbuccola.github.io/blog/...). The MathJax wasn’t rendering there. Huh.

I also noticed something else: my Google fonts were rendering on my local copy of my blog, but not on the GitHub blog. Were the issues related? Yes, they were. Here’s how.

I use the Firefox extension HTTPS-Everywhere, which tries to use the more secure https://blah.com/ instead of http://blah.com/ whenever possible. It turns out that when using the secure version of my blog, https://brianbuccola.github.io/, any insecure (http) Google font URLs or MathJax URLs won’t work. They need to all be changed to https. So that’s what I did

--mathjax="https://cdn.mathjax.org/mathjax/..."

<script src="https://cdn.mathjax.org/mathjax/..." type="text/javascript"></script>


and voilà, everything works again.

Moreover, using https URLs for Google fonts and MathJax still works when using the normal http version of my blog. So as far as I can tell, there’s no downside to always using the secure https URLs in your html source code, as far as text rendering goes.