--- aliases: - /extras/highlight/ date: 2013-07-01 menu: main: parent: extras next: /extras/toc prev: /extras/shortcodes title: Syntax Highlighting weight: 90 toc: true --- Hugo provides the ability for you to highlight source code in _two different ways_ — either pre-processed server side from your content, or to defer the processing to the client side, using a JavaScript library. **The advantage of server side** is that it doesn’t depend on a JavaScript library and consequently works very well when read from an RSS feed. **The advantage of client side** is that it doesn’t cost anything when building your site and some of the highlighting scripts available cover more languages than Pygments does. ## Server-side For the pre-processed approach, highlighting is performed by an external Python-based program called [Pygments](http://pygments.org/) and is triggered via an embedded Hugo shortcode (see example below). If Pygments is absent from the path, it will silently simply pass the content along unhighlighted. ### Pygments If you have never worked with Pygments before, here is a brief primer: + Install Python from [python.org](https://www.python.org/downloads/). Version 2.7.x is already sufficient. + Run `pip install Pygments` in order to install Pygments. Once installed, Pygments gives you a command `pygmentize`. Make sure it sits in your PATH, otherwise Hugo cannot find it. On Debian and Ubuntu systems, you may also install Pygments by running `sudo apt-get install python3-pygments`. Hugo gives you two options that you can set with the variable `pygmentsuseclasses` (default `false`) in `config.toml` (or `config.yaml`). 1. Color-codes for highlighting keywords are directly inserted if `pygmentsuseclasses = false` (default). See in the example below. The color-codes depend on your choice of the `pygmentsstyle` (default `"monokai"`). You can explore the different color styles on [pygments.org](http://pygments.org/) after inserting some example code. 2. If you choose `pygmentsuseclasses = true`, Hugo includes class names in your code instead of color-codes. For class-names to be meaningful, you need to include a `.css`-file in your website representing your color-scheme. You can either generate this `.css`-files according to this [description](http://pygments.org/docs/cmdline/) or download the standard ones from the [GitHub pygments-css repository](https://github.com/richleland/pygments-css). ### Usage Highlighting is carried out via the in-built shortcode `highlight`. `highlight` takes exactly one required parameter of language, and requires a closing shortcode. Note that `highlight` is _not_ used for client-side javascript highlighting. ### Example ``` {{}}

{{ .Title }}

{{ range .Data.Pages }} {{ .Render "summary"}} {{ end }}
{{}} ``` ### Example Output ``` <section id="main"> <div> <h1 id="title">{{ .Title }}</h1> {{ range .Data.Pages }} {{ .Render "summary"}} {{ end }} </div> </section> ``` ### Options Options to control highlighting can be added as a quoted, comma separated key-value list as the second argument in the shortcode. The example below will highlight as language `go` with inline line numbers, with line number 2 and 3 highlighted. ``` {{}} var a string var b string var c string var d string {{}} ``` Supported keywords: `style`, `encoding`, `noclasses`, `hl_lines`, `linenos`. Note that `style` and `noclasses` will override the similar setting in the global config. The keywords are the same you would using with Pygments from the command line, see the [Pygments doc](http://pygments.org/docs/) for more info. ### Disclaimers * Pygments is relatively slow and _causes a performance hit when building your site_, but Hugo has been designed to cache the results to disk. * Languages available depends on your Pygments installation. ## Client-side Alternatively, code highlighting can be done in client-side JavaScript. Client-side syntax highlighting is very simple to add. You'll need to pick a library and a corresponding theme. Some popular libraries are: - [Highlight.js] - [Prism] - [Rainbow] - [Syntax Highlighter] - [Google Prettify] ### Highlight.js example This example uses the popular [Highlight.js] library, hosted by [Yandex], a popular Russian search engine. In your `./layouts/partials/` (or `./layouts/chrome/`) folder, depending on your specific theme, there will be a snippet that will be included in every generated HTML page, such as `header.html` or `header.includes.html`. Simply add the css and js to initialize [Highlight.js]: ~~~ ~~~ ### Prism example Prism is another popular highlighter library, used on some major sites. Similar to Highlight.js, you simply load `prism.css` in your `` via whatever Hugo partial template is creating that part of your pages, like so: ```html ... ... ``` ... and add `prism.js` near the bottom of your `` tag, again in whatever Hugo partial template is appropriate for your site or theme. ```html ... ... ``` In this example, the local paths indicate that your own copy of these files are being added to the site, typically under `./static/`. ### Using Client-side highlighting To use client-side highlighting, most of these javascript libraries expect your code to be wrapped in semantically correct `` tags, with the language expressed in a class attribute on the `` tag, such as `class="language-abc"`, where the `abc` is the code the highlighter script uses to represent that language. The script would be looking for classes like `language-go`, `language-html`, or `language-css`. If you look at the page's source, it would be marked up like so: ~~~html

body {
  font-family: "Noto Sans", sans-serif;
}

~~~ The markup in your content pages (e.g. `my-css-tutorial.md`) needs to look like the following, with the name of the language to be highlighted entered directly after the first "fence", in a fenced code block:
~~~css
body {
  font-family: "Noto Sans", sans-serif;
}
~~~
When passed through the highlighter script, it would yield something like this output when viewed on your rendered page: ~~~css body { font-family: "Noto Sans", sans-serif; } ~~~ Please see individual libraries' documentation for how to implement each of the JavaScript-based libraries. [Prism]: http://prismjs.com [Highlight.js]: http://highlightjs.org/ [Rainbow]: http://craig.is/making/rainbows [Syntax Highlighter]: http://alexgorbatchev.com/SyntaxHighlighter/ [Google Prettify]: https://code.google.com/p/google-code-prettify/ [Yandex]: http://yandex.ru/