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Syntax Highlighting

Hugo comes with really fast syntax highlighting from Chroma.

2017-02-01

highlighting

pygments

chroma

code blocks

syntax

content management

docs

parent	weight
content-management	300

false

/extras/highlighting/

/extras/highlight/

/tools/syntax-highlighting/

true

From Hugo 0.28, the default syntax highlighter 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 or linenos=table (table will give copy-and-paste friendly code blocks) turns on line numbers.
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=table,hl_lines=8 15-17,linenostart=199" */>}}
// ... code
{{</* / highlight */>}}

Gives this:

{{< highlight go "linenos=table,hl_lines=8 15-17,linenostart=199" >}} // GetTitleFunc returns a func that can be used to transform a string to // title case. // // The supported styles are // // - "Go" (strings.Title) // - "AP" (see https://www.apstylebook.com/) // - "Chicago" (see http://www.chicagomanualofstyle.org/home.html) // // If an unknown or empty style is provided, AP style is what you get. func GetTitleFunc(style string) func(s string) string { switch strings.ToLower(style) { case "go": return strings.Title case "chicago": tc := transform.NewTitleConverter(transform.ChicagoStyle) return tc.Title default: tc := transform.NewTitleConverter(transform.APStyle) return tc.Title } } {{< / highlight >}}

Configure Syntax Highlighter

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. Note that this option is not relevant when pygmentsUseClasses is set.
Syntax highlighting galleries: Chroma (short snippets, long snippets), Pygments
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 HTML Formatter Documentation for details.

Generate Syntax Highlighter CSS

If you run with pygmentsUseClasses=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

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

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;

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

List of Chroma Highlighting Languages

The full list of Chroma lexers and their aliases (which is the identifier used in the highlight template func or when doing highlighting in code fences):

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.

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 %}}

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.

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