Syntax highlighting

Hugo provides several methods to add syntax highlighting to code examples:

• Use the transform.Highlight function within your templates
• Use the highlight shortcode with any content format
• Use fenced code blocks with the Markdown content format

Fenced code blocks

In its default configuration, Hugo highlights code examples within fenced code blocks, following this form:

```LANG [OPTIONS]
CODE
```

CODE

The code to highlight.

LANG

The language of the code to highlight. Choose from one of the supported languages. This value is case-insensitive.

OPTIONS

One or more space-separated or comma-separated key-value pairs wrapped in braces. Set default values for each option in your site configuration. The key names are case-insensitive.

For example, with this Markdown:

```go {linenos=inline hl_lines=[3,"6-8"] style=emacs}
package main

import "fmt"

func main() {
    for i := 0; i < 3; i++ {
        fmt.Println("Value of i:", i)
    }
}
```

Hugo renders this:

1package main
2
3import "fmt"
4
5func main() {
6    for i := 0; i < 3; i++ {
7        fmt.Println("Value of i:", i)
8    }
9}

Options

anchorLineNos

(bool) Whether to render each line number as an HTML anchor element, setting the id attribute of the surrounding span element to the line number. Irrelevant if lineNos is false. Default is false.

codeFences

(bool) Whether to highlight fenced code blocks. Default is true.

guessSyntax

(bool) Whether to automatically detect the language if the LANG argument is blank or set to a language for which there is no corresponding lexer. Falls back to a plain text lexer if unable to automatically detect the language. Default is false.

The Chroma syntax highlighter includes lexers for approximately 250 languages, but only 5 of these have implemented automatic language detection.

hl_Lines

(string) A space-delimited list of lines to emphasize within the highlighted code. To emphasize lines 2, 3, 4, and 7, set this value to 2-4 7. This option is independent of the lineNoStart option.

hl_inline

(bool) Whether to render the highlighted code without a wrapping container. Default is false.

lineAnchors

(string) When rendering a line number as an HTML anchor element, prepend this value to the id attribute of the surrounding span element. This provides unique id attributes when a page contains two or more code blocks. Irrelevant if lineNos or anchorLineNos is false.

lineNoStart

(int) The number to display at the beginning of the first line. Irrelevant if lineNos is false. Default is 1.

lineNos

(any) Controls line number display. Default is false.

• true: Enable line numbers, controlled by lineNumbersInTable.
• false: Disable line numbers.
• inline: Enable inline line numbers (sets lineNumbersInTable to false).
• table: Enable table-based line numbers (sets lineNumbersInTable to true).

lineNumbersInTable

(bool) Whether to render the highlighted code in an HTML table with two cells. The left table cell contains the line numbers, while the right table cell contains the code. Irrelevant if lineNos is false. Default is true.

noClasses

(bool) Whether to use inline CSS styles instead of an external CSS file. Default is true. To use an external CSS file, set this value to false and generate the CSS file from the command line:

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

style

(string) The CSS styles to apply to the highlighted code. Case-sensitive. Default is monokai. See syntax highlighting styles.

tabWidth

(int) Substitute this number of spaces for each tab character in your highlighted code. Irrelevant if noClasses is false. Default is 4.

wrapperClass

New in v0.140.2

(string) The class or classes to use for the outermost element of the highlighted code. Default is highlight.

Escaping

When documenting shortcode usage, escape the tag delimiters:

```text {linenos=inline}
{{</* shortcode-1 */>}}

{{%/* shortcode-2 */%}}
```

Hugo renders this to:

1{{< shortcode-1 >}}
2
3{{% shortcode-2 %}}

Languages

These are the supported languages. Use one of the identifiers, not the language name, when specifying a language for:

• The transform.Highlight function
• The highlight shortcode
• Fenced code blocks