Hierarchical Tree Structure in HTML CSS

This code snippet implements a hierarchical tree structure using HTML and CSS. It consists of nested <ul> and <li> elements to create a tree-like organization of content. Each level of the tree can be expanded or collapsed by clicking on the corresponding labels.

The code provides a visual representation of the hierarchical relationships between different levels of data. This implementation is helpful for organizing and displaying data in a structured manner, such as representing categories, file directories, or organizational hierarchies.

Moreover, the code utilizes CSS styles to control the appearance and behavior of the tree structure, allowing for customization and flexibility in its usage.

How to Create Hierarchical Tree Structure in HTML CSS

1. First of all, load the Reset CSS and PrefixFree JS by adding the following CDN links into the head tag of your HTML document.

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/meyer-reset/2.0/reset.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js"></script>

2. Create the HTML structure for the tree nav as follows and add your hierarchical data to it.

<ul class="tree">
  <li>
    <input type="checkbox" checked="checked" id="c1" />
    <label class="tree_label" for="c1">Level 0</label>
    <ul>
      <li>
        <input type="checkbox" checked="checked" id="c2" />
        <label for="c2" class="tree_label">Level 1</label>
        <ul>
          <li><span class="tree_label">Level 2</span></li>
          <li><span class="tree_label">Level 2</span></li>
        </ul>
      </li>
      <li>
        <input type="checkbox" id="c3" />
        <label for="c3" class="tree_label">Looong level 1 <br/>label text <br/>with line-breaks</label>
        <ul>
          <li><span class="tree_label">Level 2</span></li>
          <li>
            <input type="checkbox" id="c4" />
            <label for="c4" class="tree_label"><span class="tree_custom">Specified tree item view</span></label>
            <ul>
              <li><span class="tree_label">Level 3</span></li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
  </li>
  
  <li>
    <input type="checkbox" id="c5" />
    <label class="tree_label" for="c5">Level 0</label>
    <ul>
      <li>
        <input type="checkbox" id="c6" />
        <label for="c6" class="tree_label">Level 1</label>
        <ul>
          <li><span class="tree_label">Level 2</span></li>
        </ul>
      </li>
      <li>
        <input type="checkbox" id="c7" />
        <label for="c7" class="tree_label">Level 1</label>
        <ul>
          <li><span class="tree_label">Level 2</span></li>
          <li>
            <input type="checkbox" id="c8" />
            <label for="c8" class="tree_label">Level 2</label>
            <ul>
              <li><span class="tree_label">Level 3</span></li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
  </li>
</ul>

3. Now, use the following CSS code to style the hierarchical tree menu.

/* ————————————————————–
  Tree core styles
*/
.tree { margin: 1em; }

.tree input {
  position: absolute;
  clip: rect(0, 0, 0, 0);
  }

.tree input ~ ul { display: none; }

.tree input:checked ~ ul { display: block; }

/* ————————————————————–
  Tree rows
*/
.tree li {
  line-height: 1.2;
  position: relative;
  padding: 0 0 1em 1em;
  }

.tree ul li { padding: 1em 0 0 1em; }

.tree > li:last-child { padding-bottom: 0; }

/* ————————————————————–
  Tree labels
*/
.tree_label {
  position: relative;
  display: inline-block;
  }

label.tree_label { cursor: pointer; }

label.tree_label:hover { color: #666; }

/* ————————————————————–
  Tree expanded icon
*/
label.tree_label:before {
  background: #000;
  color: #fff;
  position: relative;
  z-index: 1;
  float: left;
  margin: 0 1em 0 -2em;
  width: 1em;
  height: 1em;
  border-radius: 1em;
  content: '+';
  text-align: center;
  line-height: .9em;
  }

:checked ~ label.tree_label:before { content: '–'; }

/* ————————————————————–
  Tree branches
*/
.tree li:before {
  position: absolute;
  top: 0;
  bottom: 0;
  left: -.5em;
  display: block;
  width: 0;
  border-left: 1px solid #777;
  content: "";
  }

.tree_label:after {
  position: absolute;
  top: 0;
  left: -1.5em;
  display: block;
  height: 0.5em;
  width: 1em;
  border-bottom: 1px solid #777;
  border-left: 1px solid #777;
  border-radius: 0 0 0 .3em;
  content: '';
  }

label.tree_label:after { border-bottom: 0; }

:checked ~ label.tree_label:after {
  border-radius: 0 .3em 0 0;
  border-top: 1px solid #777;
  border-right: 1px solid #777;
  border-bottom: 0;
  border-left: 0;
  bottom: 0;
  top: 0.5em;
  height: auto;
  }

.tree li:last-child:before {
  height: 1em;
  bottom: auto;
  }

.tree > li:last-child:before { display: none; }

.tree_custom {
  display: block;
  background: #eee;
  padding: 1em;
  border-radius: 0.3em;
}

To customize the hierarchical tree structure, you can modify the HTML and CSS code. Here are a few ways to customize it:

1. HTML Structure:
   • Add or remove list items (li) to represent different levels or branches of the tree.
   • Update the content of labels (label) to display your desired text or data.
   • Adjust the nesting of unordered lists (ul) to create the desired hierarchy.
2. CSS Styling:
   • Modify the margin, padding, and spacing properties to adjust the overall layout and spacing of the tree.
   • Change the background color, font properties, and border styles to customize the appearance of labels and tree nodes.
   • Adjust the colors, sizes, and shapes of icons or indicators used for expanded/collapsed states.
   • Experiment with different CSS properties to achieve the desired visual effects.

That’s all! hopefully, you have successfully created hierarchical tree structure in HTML and CSS. If you have any questions or suggestions, feel free to comment below.