jekyll-toc

Usage

Add jekyll-toc plugin in your site's Gemfile.

gem 'jekyll-toc'

And add the jekyll-toc to your site's _config.yml.

gems:
  - jekyll-toc

Set toc: true in your posts.

---
layout: post
title: "Welcome to Jekyll!"
toc: true
---

There are three Liquid filters available now, which all should be applied to some HTML content, e.g. the Liquid variable content available in Jekyll's templates.

1. toc_only
   Generates the TOC itself as described below. Mostly useful in cases where the TOC should not be placed immediately above the content but at some other place of the page, i.e. an aside.

2. inject_anchors
   Injects HTML anchors into the content without actually outputing the TOC itself. They are of the form:

   <a id="heading11" class="anchor" href="#heading1-1" aria-hidden="true">
     <span class="octicon octicon-link"></span>
   </a>

This is only useful when the TOC itself should be placed at some other location with the toc_only filter.

1. toc
   This is the concatenation of the two above, where the TOC is placed directly above the content.

Add toc filter to your site's {{ content }} (e.g. _layouts/post.html).

  {{ content | toc }}

Generated Table of Contents HTML

jekyll-toc generates Unordered List. The final output is as follows.

<ul class="section-nav">
  <li class="toc-entry toc-h1"><a href="#heading1">Heading.1</a></li>
  <li class="toc-entry toc-h2"><a href="#heading2-1">Heading.2-1</a></li>
  <li class="toc-entry toc-h2"><a href="#heading2-2">Heading.2-2</a></li>
  <li class="toc-entry toc-h3"><a href="#heading3">Heading.3</a></li>
  <li class="toc-entry toc-h2"><a href="#heading2-3">Heading.2-3</a></li>
</ul>

It looks like the image below.

CSS Styling

The toc can be modified with CSS. The sample CSS is the following.

.section-nav {
  background-color: #FFF;
  margin: 5px 0;
  padding: 10px 30px;
  border: 1px solid #E8E8E8;
  border-radius: 3px;
}

Each TOC li entry has two CSS classes for further styling. The general toc-entry is applied to all li elements in the ul.section-nav. Depending on the heading level each specific entry refers to, it has a second CSS class toc-XX, where XX is the HTML heading tag name.

For example, the TOC entry linking to a heading <h1>...</h1> (a single # in Markdown) will get the CSS class toc-h1.

That way, one can tune the depth of the TOC displayed on the site.
The following CSS will display only the first two heading levels and hides all other links:

.toc-entry.toc-h1,
.toc-entry.toc-h2
{}
.toc-entry.toc-h3,
.toc-entry.toc-h4,
.toc-entry.toc-h5,
.toc-entry.toc-h6
{
  display: none;
}