hugo/docs/content/tools/syntax-highlighting.md

title	linktitle	description	date	publishdate	lastmod	keywords	categories	menu	weight	sections_weight	draft	aliases	toc
Syntax Highlighting		Hugo provides server-side syntax highlighting via Pygments and, like most static site generators, works very well with client-side (JavaScript) syntax highlighting libraries as well.	2017-02-01	2017-02-01	2017-02-01	highlighting pygments code blocks syntax	developer tools	docs parent weight tools 20	20	20	false	/extras/highlighting/ /extras/highlight/	true

Hugo can 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.

Server-side

For the pre-processed approach, highlighting is performed by an external Python-based program called Pygments 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 without highlighting.

Server-side Advantages

The advantages of server-side syntax highlighting are that it doesn’t depend on a JavaScript library and, consequently, works very well when read from an RSS feed.

Pygments

If you have never worked with Pygments before, here is a brief primer:

• Install Python from python.org. 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 will not be able to find and use 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 your site configuration.

1. Color codes for highlighting keywords are directly inserted if pygmentsuseclasses = false (default). The color codes depend on your choice of the pygmentsstyle (default = "monokai"). You can explore the different color styles on 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 the description from the Pygments documentation or download the one of the many pre-built color schemes from Pygment's GitHub css repository.

Server-side Usage

Highlighting is carried out via the built-in shortcode highlight. highlight takes exactly one required parameter for the programming language to be highlighted and requires a closing shortcode. Note that highlight is not used for client-side javascript highlighting.

Example highlight Shortcode Input

{{< code file="example-highlight-shortcode-input.md" >}} {{</* highlight html */>}}

{{ .Title }}

{{ range .Data.Pages }} {{ .Render "summary"}} {{ end }}

{{}} {{< /code >}}

Example highlight Shortcode Output

{{< output file="example-highlight-shortcode-output.html" >}} <section id="main"> <div> <h1 id="title">{{ .Title }}</h1> {{ range .Data.Pages }} {{ .Render "summary"}} {{ end }} </div> </section> {{< /output >}}

Options

Options for controlling highlighting can be added in the second argument as a quoted, comma-separated key-value list. The example below will syntax highlight in go with inline line numbers and line numbers 2 and 3 highlighted.

{{</* highlight go "linenos=inline,hl_lines=2 3" */>}}
var a string
var b string
var c string
var d string
{{</* / highlight */>}}

The highlight shortcode includes the following supported keywords:

• style
• encoding
• noclasses
• hl_lines
• linenos

Note that style and noclasses will override the similar setting in the global config.

The keywords in the highlight shortcode mirror those of Pygments from the command line. See the Pygments documentation for more information.

Code Fences

It is also possible to add syntax highlighting with GitHub flavored code fences. To enable this, set the PygmentsCodeFences to true in Hugo's configuration file;

```
<section id="main">
  <div>
    <h1 id="title">{{ .Title }}</h1>
    {{ range .Data.Pages }}
      {{ .Render "summary"}}
    {{ end }}
  </div>
</section>
```

{{% note "Disclaimers on Pygments" %}}

• Pygments is relatively slow and causes a performance hit when building your site, but Hugo has been designed to cache the results to disk.
• The caching can be turned off by setting the --ignoreCache flag to true.
• The languages available for highlighting depend on your Pygments installation. {{% /note %}}

Client-side

Alternatively, code highlighting can be applied to your code blocks 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

Client-side Advantages

The advantages of client-side syntax highlighting are that it doesn’t cost anything when building your site, and some of the highlighting scripts available cover more languages than Pygments does.

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:

<link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.6.0/styles/default.min.css">
<script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.6.0/highlight.min.js"></script>
<script>hljs.initHighlightingOnLoad();</script>

Prism example

Prism is another popular highlighter library and is used on some major sites. The download section of the prism.js website is simple to use and affords you a high degree of customization to pick only the languages you'll be using on your site.

Similar to Highlight.js, you simply load prism.css in your <head> via whatever Hugo partial template is creating that part of your pages:

...
<link href="/css/prism.css" rel="stylesheet" />
...

Add prism.js near the bottom of your <body> tag in whatever Hugo partial template is appropriate for your site or theme.

...
<script src="/js/prism.js"></script>
</body>

In this example, the local paths indicate that your downloaded copy of these files are being added to the site, typically under ./static/css/ and ./static/js/, respectively.

Client-side Usage

To use client-side highlighting, most of these javascript libraries expect your code to be wrapped in semantically correct <code> elements with language-specific class attributes. For example, a code block for HTML would have class="language-html".

The client-side highlighting script therefore looks for programming language classes according to this convention: language-go, language-html, language-css, language-bash, etc. If you look at the page's source, you might see something like the following:

<pre>
  <code class="language-css">
  body {
    font-family: "Noto Sans", sans-serif;
  }
  </code>
</pre>

If you are using markdown, your content pages needs to use the following syntax, with the name of the language to be highlighted entered directly after the first "fence." A fenced code block can be noted by opening and closing triple tilde ~ or triple back ticks `:

{{< nohighlight >}}

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

{{< /nohighlight >}}

Here is the same example but with triple back ticks to denote the fenced code block:

{{< nohighlight >}}

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

{{< /nohighlight >}}

Passing the above examples through the highlighter script would yield the following markup:

{{< nohighlight >}} <pre><code class="language-css hljs">;<span class="hljs-selector-tag">body</span> { <span class="hljs-attribute">font-family</span>: &ltspan class="hljs-string">"Noto Sans"</span>, sans-serif; } {{< /nohighlight >}}

In the case of the coding color scheme used by the Hugo docs, the resulting output would then look like the following to the website's end users:

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

Please see individual libraries' documentation for how to implement each of the JavaScript-based libraries.