Syntax Highlighting

From Hugo 0.28, the default syntax hightlighter in Hugo is Chroma; it is built in Go and is really, really fast – and for the most important parts compatible with Pygments.

If you want to continue to use Pygments (see below), set pygmentsUseClassic=true in your site config.

The example below shows a simple code snippet from the Hugo source highlighted with the highlight shortcode. Note that the gohugo.io site is generated with pygmentsUseClasses=true (see Generate Syntax Highlighter CSS).

• linenos=inline turns on line numbers. Note that the inline value only has an effect in Pygments.
• hl_lines lists a set of line numbers or line number ranges to be highlighted. Note that the hyphen range syntax is only supported for Chroma.
• linenostart=199 starts the line number count from 199.

With that, this:

{{< highlight go "linenos=inline,hl_lines=8 15-17,linenostart=199" >}}
// ... code
{{< / highlight >}}

Gives this:

199// GetTitleFunc returns a func that can be used to transform a string to
200// title case.
201//
202// The supported styles are
203//
204// - "Go" (strings.Title)
205// - "AP" (see https://www.apstylebook.com/)
206// - "Chicago" (see http://www.chicagomanualofstyle.org/home.html)
207//
208// If an unknown or empty style is provided, AP style is what you get.
209func GetTitleFunc(style string) func(s string) string {
210  switch strings.ToLower(style) {
211  case "go":
212    return strings.Title
213  case "chicago":
214    tc := transform.NewTitleConverter(transform.ChicagoStyle)
215    return tc.Title
216  default:
217    tc := transform.NewTitleConverter(transform.APStyle)
218    return tc.Title
219  }
220}

Configure Syntax Hightlighter

To make the transition from Pygments to Chroma seamless, they share a common set of configuration options:

pygmentsOptions

A comma separated list of options. See below for a full list.

pygmentsCodefences

Set to true to enable syntax highlighting in code fences with a language tag in markdown (see below for an example).

pygmentsStyle

The style of code highlighting. See https://help.farbox.com/pygments.html for a gallery. Note that this option is not relevant when pygmentsUseClasses is set.

pygmentsUseClasses

Set to true to use CSS classes to format your highlighted code. See Generate Syntax Highlighter CSS.

pygmentsCodefencesGuessSyntax

Set to true to try to do syntax highlighting on code fenced blocks in markdown without a language tag.

pygmentsUseClassic

Set to true to use Pygments instead of the much faster Chroma.

Options

pygmentsOptions can be set either in site config or overridden per code block in the Highlight shortcode or template func.

noclasses

Use inline style.

linenos

For Chroma, any value in this setting will print line numbers. Pygments has some more fine grained control.

linenostart

Start the line numbers from this value (default is 1).

hl_lines

Highlight a space separated list of line numbers. For Chroma, you can provide a list of ranges, i.e. “3-8 10-20”.

The full set of supported options for Pygments is: encoding, outencoding, nowrap, full, title, style, noclasses, classprefix, cssclass, cssstyles, prestyles, linenos, hl_lines, linenostart, linenostep, linenospecial, nobackground, lineseparator, lineanchors, linespans, anchorlinenos, startinline. See the Pygments Documentation for details.

Generate Syntax Highlighter CSS

If you run with pygmentsUseClassic=true in your site config, you need a style sheet.

You can generate one with Hugo:

hugo gen chromastyles --style=monokai > syntax.css

Run hugo gen chromastyles -h for more options. See https://help.farbox.com/pygments.html for a gallery of available styles.

Highlight Shortcode

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

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

Highlight Template Func

See Highlight.

Highlight in 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;

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

Highlight with Pygments Classic

If you for some reason don’t want to use the built-in Chroma highlighter, you can set pygmentsUseClassic=true in your config and add Pygments to your path.

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.