If you’d like to include custom liquid tags in your site, you can do so by hooking into the tagging system. Built-in examples added by Jekyll include the highlight and include tags. Below is an example of a custom liquid tag that will output the time the page was rendered:

module Jekyll
  class RenderTimeTag < Liquid::Tag

    def initialize(tag_name, text, tokens)
      super
      @text = text
    end

    def render(context)
      "#{@text} #{Time.now}"
    end
  end
end

Liquid::Template.register_tag('render_time', Jekyll::RenderTimeTag)

At a minimum, liquid tags must implement:

You must also register the custom tag with the Liquid template engine as follows:

Liquid::Template.register_tag('render_time', Jekyll::RenderTimeTag)

In the example above, we can place the following tag anywhere in one of our pages:

<p>{% render_time page rendered at: %}</p>

And we would get something like this on the page:

<p>page rendered at: Tue June 22 23:38:47 –0500 2010</p>

Tag Blocks

The render_time tag seen above can also be rewritten as a tag block by inheriting the Liquid::Block class. Look at the example below:

module Jekyll
  class RenderTimeTagBlock < Liquid::Block

    def render(context)
      text = super
      "<p>#{text} #{Time.now}</p>"
    end

  end
end

Liquid::Template.register_tag('render_time', Jekyll::RenderTimeTagBlock)

We can now use the tag block anywhere:

{% render_time %}
page rendered at:
{% endrender_time %}

And we would still get the same output as above on the page:

<p>page rendered at: Tue June 22 23:38:47 –0500 2010</p>

In the above example, the tag block and the tag are both registered with the name render_time, but to register a tag and a tag block using the same name in the same project is not recommended as this may lead to conflicts.