# Equation numbers in blog posts with MathJax.

13 Feb 2022How do you get MathJax to output equation numbers, and maybe reference them with a number and hyperlink?

Links:

I found the documentation a little confusing, I’ll note what I did that worked.

First, I set up a local configuration (MathJax configuration docs) by creating a file `mathjax-config.js`

within a directory `/js`

, so the full path is `/js/mathjax-config.js`

. This file has the following contents:

```
window.MathJax = {
tex: {
tags: 'all'
}
};
```

On a page where I want equation numbering, I have the following underneath the liquid header:

```
<script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script>
<script src="/js/mathjax-config.js" defer></script>
<script type="text/javascript" id="MathJax-script" async
src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-svg.js">
</script>
```

Let’s go back to Eq. \eqref{eqone}.

Let’s write another equation:

\[a + b = c \label{eqtwo}\]Here I’m going to write some filler …. then make the window really short, so that you can test references, and …

And now I want to reference both Eq.s \eqref{eqone} and \eqref{eqtwo}.

To be honest, the equation references for the first equation work, but the reference goes to just below the second equation. So I’m still working on the reference part.

*Update: on another page that is much bigger, and with more equations, the equation hyperlinks go to the right place.*

The markdown for the above is:

```
$$e^{\pi i} + 1 = 0 \label{eqone}$$
Let's go back to Eq. \eqref{eqone}.
Let's write another equation:
$$a + b = c \label{eqtwo}$$
Here I'm going to write some filler ....
then make the window really short,
so that you can test references, and ...
And now I want to reference both Eq.s \eqref{eqone} and \eqref{eqtwo}.
```