Introduction to templating

A template is a file in the layouts directory of a project, theme, or module. Templates use variables , functions, and methods to transform your content, resources, and data into a published page.

For example, this HTML template initializes the $v1 and $v2 variables, then displays them and their product within an HTML paragraph.

{{ $v1 := 6 }}
{{ $v2 := 7 }}
<p>The product of {{ $v1 }} and {{ $v2 }} is {{ mul $v1 $v2 }}.</p>

While HTML templates are the most common, you can create templates for any output format including CSV, JSON, RSS, and plain text.

Context

The most important concept to understand before creating a template is context, the data passed into each template. The data may be a simple value, or more commonly objects and associated methods.

For example, a template for a single page receives a Page object, and the Page object provides methods to return values or perform actions.

Current context

Within a template, the dot (.) represents the current context.

<h2>{{ .Title }}</h2>

In the example above the dot represents the Page object, and we call its Title method to return the title as defined in front matter.

The current context may change within a template. For example, at the top of a template the context might be a Page object, but we rebind the context to another value or object within range or with blocks.

<h2>{{ .Title }}</h2>

{{ range slice "foo" "bar" }}
  <p>{{ . }}</p>
{{ end }}

{{ with "baz" }}
  <p>{{ . }}</p>
{{ end }}

In the example above, the context changes as we range through the slice of values. In the first iteration the context is “foo”, and in the second iteration the context is “bar”. Inside of the with block the context is “baz”. Hugo renders the above to:

<h2>My Page Title</h2>
<p>foo</p>
<p>bar</p>
<p>baz</p>

Template context

Within a range or with block you can access the context passed into the template by prepending a dollar sign ($) to the dot:

{{ with "foo" }}
  <p>{{ $.Title }} - {{ . }}</p>
{{ end }}

Hugo renders this to:

<p>My Page Title - foo</p>

Actions

In the examples above the paired opening and closing braces represent the beginning and end of a template action, a data evaluation or control structure within a template.

A template action may contain literal values (boolean, string, integer, and float), variables, functions, and methods.

{{ $convertToLower := true }}
{{ if $convertToLower }}
  <h2>{{ strings.ToLower .Title }}</h2>
{{ end }}

In the example above:

• $convertToLower is a variable
• true is a literal boolean value
• strings.ToLower is a function that converts all characters to lowercase
• Title is a method on a the Page object

Hugo renders the above to:

  
  
    <h2>my page title</h2>
  

Whitespace

Notice the blank lines and indentation in the previous example? Although irrelevant in production when you typically minify the output, you can remove the adjacent whitespace by using template action delimiters with hyphens:

{{- $convertToLower := true -}}
{{- if $convertToLower -}}
  <h2>{{ strings.ToLower .Title }}</h2>
{{- end -}}

Hugo renders this to:

<h2>my page title</h2>

Whitespace includes spaces, horizontal tabs, carriage returns, and newlines.

Pipes

Within a template action you may pipe a value to function or method. The piped value becomes the final argument to the function or method. For example, these are equivalent:

{{ strings.ToLower "Hugo" }} → hugo
{{ "Hugo" | strings.ToLower }} → hugo

You can pipe the result of one function or method into another. For example, these are equivalent:

{{ strings.TrimSuffix "o" (strings.ToLower "Hugo") }} → hug
{{ "Hugo" | strings.ToLower | strings.TrimSuffix "o" }} → hug

These are also equivalent:

{{ mul 6 (add 2 5) }} → 42
{{ 5 | add 2 | mul 6 }} → 42

Line splitting

You can split a template action over two or more lines. For example, these are equivalent:

{{ $v := or .Site.Language.LanguageName .Site.Language.Lang }}

{{ $v := or 
  .Site.Language.LanguageName
  .Site.Language.Lang
}}

You can also split raw string literals over two or more lines. For example, these are equivalent:

{{ $msg := "This is line one.\nThis is line two." }}

{{ $msg := `This is line one.
This is line two.`
}}

Variables

A variable is a user-defined identifier prepended with a dollar sign ($), representing a value of any data type, initialized or assigned within a template action. For example, $foo and $bar are variables.

Variables may contain scalars, slices, maps, or objects.

Use := to initialize a variable, and use = to assign a value to a variable that has been previously initialized. For example:

{{ $total := 3 }}
{{ range slice 7 11 21 }}
  {{ $total = add $total . }}
{{ end }}
{{ $total }} → 42

Variables initialized inside of an if, range, or with block are scoped to the block. Variables initialized outside of these blocks are scoped to the template.

With variables that represent a slice or map, use the index function to return the desired value.

{{ $slice := slice "foo" "bar" "baz" }}
{{ index $slice 2 }} → baz

{{ $map := dict "a" "foo" "b" "bar" "c" "baz" }}
{{ index $map "c" }} → baz

With variables that represent a map or object, chain identifiers to return the desired value or to access the desired method.

{{ $map := dict "a" "foo" "b" "bar" "c" "baz" }}
{{ $map.c }} → baz

{{ $homePage := .Site.Home }}
{{ $homePage.Title }} → My Homepage

Functions

Used within a template action, a function takes one or more arguments and returns a value. Unlike methods, functions are not associated with an object.

Go’s text/template and html/template packages provide a small set of functions, operators, and statements for general use. See the go-templates section of the function documentation for details.

Hugo provides hundreds of custom functions categorized by namespace. For example, the strings namespace includes these and other functions:

As shown above, frequently used functions have an alias. Use aliases in your templates to reduce code length.

When calling a function, separate the arguments from the function, and from each other, with a space. For example:

{{ $total := add 1 2 3 4 }}

Methods

Used within a template action and associated with an object, a method takes zero or more arguments and either returns a value or performs an action.

The most commonly accessed objects are the Page and Site objects. This is a small sampling of the methods available to each object.

Chain the method to its object with a dot (.) as shown below, remembering that the leading dot represents the current context.

{{ .Site.Title }} → My Site Title
{{ .Page.Title }} → My Page Title

The context passed into most templates is a Page object, so this is equivalent to the previous example:

{{ .Site.Title }} → My Site Title
{{ .Title }} → My Page Title

Some methods take an argument. Separate the argument from the method with a space. For example:

{{ $page := .Page.GetPage "/books/les-miserables" }}
{{ $page.Title }} → Les Misérables

Comments

Template comments are similar to template actions. Paired opening and closing braces represent the beginning and end of a comment. For example:

{{/* This is an inline comment. */}}
{{- /* This is an inline comment with adjacent whitespace removed. */ -}}

Code within a comment is not parsed, executed, or displayed. Comments may be inline, as shown above, or in block form:

{{/*
This is a block comment.
*/}}

{{- /*
This is a block comment with
adjacent whitespace removed.
*/ -}}

You may not nest one comment inside of another.

To render an HTML comment, pass a string through the safeHTML template function. For example:

{{ "<!-- I am an HTML comment. -->" | safeHTML }}
{{ printf "<!-- This is the %s site. -->" .Site.Title | safeHTML }}

Include

Use the template function to include one or more of Hugo’s embedded templates:

{{ template "_internal/google_analytics.html" . }}
{{ template "_internal/opengraph" . }}
{{ template "_internal/pagination.html" . }}
{{ template "_internal/schema.html" . }}
{{ template "_internal/twitter_cards.html" . }}

Use the partial or partialCached function to include one or more partial templates:

{{ partial "breadcrumbs.html" . }}
{{ partialCached "css.html" . }}

Create your partial templates in the layouts/partials directory.

Examples

This limited set of contrived examples demonstrates some of concepts described above. Please see the functions, methods, and templates documentation for specific examples.

Conditional blocks

See documentation for if, else, and end.

{{ $var := 42 }}
{{ if eq $var 6 }}
  {{ print "var is 6" }}
{{ else if eq $var 7 }}
  {{ print "var is 7" }}
{{ else if eq $var 42 }}
  {{ print "var is 42" }}
{{ else }}
  {{ print "var is something else" }}
{{ end }}

Logical operators

See documentation for and and or.

{{ $v1 := true }}
{{ $v2 := false }}
{{ $v3 := false }}
{{ $result := false }}

{{ if and $v1 $v2 $v3 }}
  {{ $result = true }}
{{ end }}
{{ $result }} → false

{{ if or $v1 $v2 $v3 }}
  {{ $result = true }}
{{ end }}
{{ $result }} → true

Loops

See documentation for range, else, and end.

{{ $s := slice "foo" "bar" "baz" }}
{{ range $s }}
  <p>{{ . }}</p>
{{ else }}
  <p>The collection is empty</p>
{{ end }}

Use the seq function to loop a specified number of times:

{{ $total := 0 }}
{{ range seq 4 }}
  {{ $total = add $total . }}
{{ end }}
{{ $total }} → 10

Rebind context

See documentation for with, else, and end.

{{ $var := "foo" }}
{{ with $var }}
  {{ . }} → foo
{{ else }}
  {{ print "var is falsy" }}
{{ end }}

To test multiple conditions:

{{ $v1 := 0 }}
{{ $v2 := 42 }}
{{ with $v1 }}
  {{ . }}
{{ else with $v2 }}
  {{ . }} → 42
{{ else }}
  {{ print "v1 and v2 are falsy" }}
{{ end }}

Access site parameters

See documentation for the Params method on a Site object.

With this site configuration:

baseURL: https://example.org
params:
  author:
    email: [email protected]
    name: John Smith
  copyright-year: "2023"
  layouts:
    rfc_1123: Mon, 02 Jan 2006 15:04:05 MST
    rfc_3339: "2006-01-02T15:04:05-07:00"
  subtitle: The Best Widgets on Earth
title: ABC Widgets

baseURL = 'https://example.org'
title = 'ABC Widgets'
[params]
  copyright-year = '2023'
  subtitle = 'The Best Widgets on Earth'
  [params.author]
    email = '[email protected]'
    name = 'John Smith'
  [params.layouts]
    rfc_1123 = 'Mon, 02 Jan 2006 15:04:05 MST'
    rfc_3339 = '2006-01-02T15:04:05-07:00'

{
   "baseURL": "https://example.org",
   "params": {
      "author": {
         "email": "[email protected]",
         "name": "John Smith"
      },
      "copyright-year": "2023",
      "layouts": {
         "rfc_1123": "Mon, 02 Jan 2006 15:04:05 MST",
         "rfc_3339": "2006-01-02T15:04:05-07:00"
      },
      "subtitle": "The Best Widgets on Earth"
   },
   "title": "ABC Widgets"
}

Access the custom site parameters by chaining the identifiers:

{{ .Site.Params.subtitle }} → The Best Widgets on Earth
{{ .Site.Params.author.name }} → John Smith

{{ $layout := .Site.Params.layouts.rfc_1123 }}
{{ .Site.Lastmod.Format $layout }} → Tue, 17 Oct 2023 13:21:02 PDT

Access page parameters

See documentation for the Params method on a Page object.

With this front matter:

date: 2023-10-17T15:11:37-07:00
params:
  author:
    email: [email protected]
    name: John Smith
  display_related: true
title: Annual conference

date = 2023-10-17T15:11:37-07:00
title = 'Annual conference'
[params]
  display_related = true
  [params.author]
    email = '[email protected]'
    name = 'John Smith'

{
   "date": "2023-10-17T15:11:37-07:00",
   "params": {
      "author": {
         "email": "[email protected]",
         "name": "John Smith"
      },
      "display_related": true
   },
   "title": "Annual conference"
}

Access the custom page parameters by chaining the identifiers:

{{ .Params.display_related }} → true
{{ .Params.author.name }} → John Smith