How can I add chevron icons to Bootstrap 3 accordion panels to visually indicate their collapse state using CSS?

Using CSS to Display Chevron Icons for Collapse States

In the Bootstrap 3 framework, the accordion component is commonly used to create collapsible panels. While the default functionality of these panels includes toggling their visibility, users may wish to further enhance this by visually displaying the current collapse state using chevron icons.

CSS Approach

The following CSS approach can be used to add chevrons to the panel headings:

.panel-heading .accordion-toggle:after {
    /* symbol for "opening" panels */
    font-family: 'Glyphicons Halflings';  /* essential for enabling glyphicon */
    content: "\e114";    /* adjust as needed, taken from bootstrap.css */
    float: right;        /* adjust as needed */
    color: grey;         /* adjust as needed */
}
.panel-heading .accordion-toggle.collapsed:after {
    /* symbol for "collapsed" panels */
    content: "\e080";    /* adjust as needed, taken from bootstrap.css */
}

To use this approach, add the above CSS to your style sheet. This will add chevrons to the panel headings, with opened panels displaying a downward-facing chevron and collapsed panels displaying an upward-facing chevron.

Example HTML

With this CSS in place, the following HTML will produce collapsible panels with chevron icons:

<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://code.jquery.com/jquery-1.11.1.min.js" type="text/javascript"></script>
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js" type="text/javascript"></script>

<div class="panel-group">

This approach enhances the user experience by providing visual cues to the panel's current state, making it easier for users to understand and interact with the collapsible panels.

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