KaTeX is the new development from Khan Academy for super fast mathematics typesetting on your website. It renders your equations into pure CSS and HTML using a small JS file, making it orders of magnitude faster than the mainstream alternative, MathJax.

This small plugin integrates KaTeX into your Jekyll website utilising Liquid blocks, so rendering an equation is as simple as writing {% latex %} equation {% endlatex %}. It is intended to be lightweight and add no appreciable compilation time to your site, even if you have many equations.

Because the KaTeX JavaScript is being run server-side through the execjs Ruby gem, you don't even need to include the KaTeX JS in the resulting web page, only the CSS and fonts!

To install it, copy katex_block.rb into the _plugins folder of your Jekyll project.

You can download the script directly by running

wget https://raw.githubusercontent.com/drewsberry/jekyll-katex-block/master/katex_block.rb
mv katex_block.rb /path/to/your/site/_plugins/

Or by cloning the whole repo and copying it across

git clone https://github.com/drewsberry/jekyll-katex-block.git
cp jekyll-katex-block/katex_block.rb /path/to/your/site/_plugins/

You also need the KaTeX CSS file, katex.min.css, and the KaTeX font files copied into your project. To download these and for more information, head over to KaTeX GitHub Page and the KaTeX source repo.

For a fully working example, check out the test directory. It contains a minimal working example of using the plugin.

To use it in a post, wrap your equation in a latex block as follows:

{% latex %} E = mc^2 {% endlatex %}

And that's it!

If you also want to have centred equations, you can do:

{% latex centred %} E = mc^2 {% endlatex %}

It's really as simple as that. This is intended to be a virtually weightless extension to your Jekyll blog that allows you to leverage the virtually weightless KaTeX CSS for incredibly fast and easy mathematics typesetting.

There is currently one global option, which is the relative path from the root of your Jekyll project to the KaTeX javascript file; you can change it in your config.yml like so:

katex:
    path_to_js: "./your/path/to/katex/js"

The default value is ./public/js/katex.min.js.

The only real problem is that being relatively new, KaTeX doesn't yet support all mathematical symbols that you might need. Several important PRs are in the works over at https://github.com/Khan/KaTeX/pulls, in particular #151 which adds vital symbols like \nabla, \imath, \hbar, \exists and a load of others.