I added tags on my top page and every posts without plugin.

Today, I’ll introduce how to add tags on Jekyll.

Step 1

Add tags on your post. For example, this article has tags like this.

tags: Jekyll Ruby

Step 2

Then each post has tags variable. You can access these tags by the following code from index.html.

<div class="home">
  <h1 class="page-heading">Posts</h1>
  <ul class="post-list">
    {% for post in site.posts %}
        <span class="post-meta">{{ post.date | date: "%b %-d, %Y" }}</span>
          <a class="post-link" href="{{ post.url | prepend: site.baseurl }}">{{ post.title | escape }}</a>
        {% for tag in post.tags %}
          <span class="label">{{tag}}</span>
        {% endfor %}
    {% endfor %}
  <p class="rss-subscribe">subscribe <a href="{{ "/feed.xml" | prepend: site.baseurl }}">via RSS</a></p>

Step 3

In step 2, you can access tags via post in site.posts. From each page, you can access it via page variable. See the following example.

<article class="post" itemscope itemtype="http://schema.org/BlogPosting">
  <header class="post-header">
    <p class="post-meta"><time datetime="{{ page.date | date_to_xmlschema }}" itemprop="datePublished">{{ page.date | date: "%b %-d, %Y" }}</time></p>
    <h1 class="post-title" itemprop="name headline">{{ page.title | escape }}</h1>
    {% for tag in page.tags %}
      <span class="label">{{tag}}</span>
    {% endfor %}

  <div class="post-content" itemprop="articleBody">
    {{ content }}

Step 4

Finally, you just add some cool styles to tags.

Entire code is here, please use that as reference.