The include tag allows you to include the content from another file stored in the _includes folder:

{% include footer.html %}

Jekyll will look for the referenced file (in this case, footer.html) in the _includes directory at the root of your source directory and insert its contents.

Including files relative to another file

You can choose to include file fragments relative to the current file by using the include_relative tag:

{% include_relative somedir/footer.html %}

You won’t need to place your included content within the _includes directory. Instead, the inclusion is specifically relative to the file where the tag is being used. For example, if _posts/2014-09-03-my-file.markdown uses the include_relative tag, the included file must be within the _posts directory or one of its subdirectories.

Note that you cannot use the ../ syntax to specify an include location that refers to a higher-level directory.

All the other capabilities of the include tag are available to the include_relative tag, such as variables.

Using variables names for the include file

The name of the file you want to embed can be specified as a variable instead of an actual file name. For example, suppose you defined a variable in your page’s front matter like this:

title: My page
my_variable: footer_company_a.html

You could then reference that variable in your include:

{% include {{ page.my_variable }} %}

In this example, the include would insert the file footer_company_a.html from the _includes/footer_company_a.html directory.

Passing parameters to includes

You can also pass parameters to an include. For example, suppose you have a file called note.html in your _includes folder that contains this formatting:

<div markdown="span" class="alert alert-info" role="alert">
<i class="fa fa-info-circle"></i> <b>Note:</b>
{{ include.content }}

The {{ include.content }} is a parameter that gets populated when you call the include and specify a value for that parameter, like this:

{% include note.html content="This is my sample note." %} 

The value of content (which is This is my sample note) will be inserted into the {{ include.content }} parameter.

Passing parameters to includes is especially helpful when you want to hide away complex formatting from your Markdown content.

For example, suppose you have a special image syntax with complex formatting, and you don’t want your authors to remember the complex formatting. As a result, you decide to simplify the formatting by using an include with parameters. Here’s an example of the special image syntax you might want to populate with an include:

   <a href="">
   <img src="logo.png" style="max-width: 200px;"
      alt="Jekyll logo" />
   <figcaption>This is the Jekyll logo</figcaption>

You could templatize this content in your include and make each value available as a parameter, like this:

   <a href="{{ include.url }}">
   <img src="{{ include.file }}" style="max-width: {{ include.max-width }};"
      alt="{{ include.alt }}"/>
   <figcaption>{{ include.caption }}</figcaption>

This include contains 5 parameters:

  • url
  • max-width
  • file
  • alt
  • caption

Here’s an example that passes all the parameters to this include (the include file is named image.html):

{% include image.html url=""
max-width="200px" file="logo.png" alt="Jekyll logo"
caption="This is the Jekyll logo." %} 

The result is the original HTML code shown earlier.

To safeguard situations where users don’t supply a value for the parameter, you can use Liquid’s default filter.

Overall, you can create includes that act as templates for a variety of uses — inserting audio or video clips, alerts, special formatting, and more. However, note that you should avoid using too many includes, as this will slow down the build time of your site. For example, don’t use includes every time you insert an image. (The above technique shows a use case for special images.)

Passing parameter variables to includes

Suppose the parameter you want to pass to the include is a variable rather than a string. For example, you might be using {{ site.product_name }} to refer to every instance of your product rather than the actual hard-coded name. (In this case, your _config.yml file would have a key called product_name with a value of your product’s name.)

The string you pass to your include parameter can’t contain curly braces. For example, you can’t pass a parameter that contains this: "The latest version of {{ site.product_name }} is now available."

If you want to include this variable in your parameter that you pass to an include, you need to store the entire parameter as a variable before passing it to the include. You can use capture tags to create the variable:

{% capture download_note %}The latest version of
{{ site.product_name }} is now available.{% endcapture %}

Then pass this captured variable into the parameter for the include. Omit the quotation marks around the parameter content because it’s no longer a string (it’s a variable):

{% include note.html content=download_note %}

Passing references to YAML files as parameter values

Instead of passing string variables to the include, you can pass a reference to a YAML data file stored in the _data folder.

Here’s an example. In the _data folder, suppose you have a YAML file called profiles.yml. Its content looks like this:

- name: John Doe
  login_age: old
  image: johndoe.jpg

- name: Jane Doe
  login_age: new
  image: janedoe.jpg

In the _includes folder, assume you have a file called spotlight.html with this code:

{% for person in {{ include.participants }} %}
{% if person.login_age == "new" %}
{{ }}
{% endif %}
{% endfor %}

Now when you insert the spotlight.html include file, you can submit the YAML file as a parameter:

{% include spotlight.html %}

In this instance, gets inserted in place of {{ include.participants }} in the include file, and the Liquid logic processes. The result will be Jane Doe.