I am using this markup for a Boostrap accordion/collapsible panel. How can I have ALL my sections open on page load instead of collapsed?

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
    <div class="panel panel-default">
        <div class="panel-heading" role="tab" id="headingOne">
            <h4 class="panel-title">
                <a class="collapsed accordion-toggle" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="false" aria-controls="collapseOne"> Header </a>
            </h4>
        </div>
        <div id="collapseOne" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingOne">
            <div class="panel-body">
                collapsible stuff
            </div>
        </div>
    </div>
</div>

I am using this markup for a Boostrap accordion/collapsible panel. How can I have ALL my sections open on page load instead of collapsed?

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
    <div class="panel panel-default">
        <div class="panel-heading" role="tab" id="headingOne">
            <h4 class="panel-title">
                <a class="collapsed accordion-toggle" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="false" aria-controls="collapseOne"> Header </a>
            </h4>
        </div>
        <div id="collapseOne" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingOne">
            <div class="panel-body">
                collapsible stuff
            </div>
        </div>
    </div>
</div>

• javascript
• jquery
• twitter-bootstrap

• Possible duplicate of twitter bootstrap collapse first item & open second item on load – isherwood Commented Feb 16, 2017 at 21:16
• it's not, I want all my sections open. Not just the first. – noclist Commented Feb 16, 2017 at 21:19
• Yes, but the same technique applies. – isherwood Commented Feb 16, 2017 at 21:24

2 Answers 2

You just have to add the classname in to the div.collapse element.

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
    <div class="panel panel-default">
        <div class="panel-heading" role="tab" id="headingOne">
            <h4 class="panel-title">
                <a class="collapsed accordion-toggle" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="false" aria-controls="collapseOne"> Header </a>
            </h4>
        </div>
        <div id="collapseOne" class="panel-collapse collapse in" role="tabpanel" aria-labelledby="headingOne">
            <div class="panel-body">
                collapsible stuff
            </div>
        </div>
    </div>
</div>

http://www.bootply./Gld6UPkkuL

<script src="https://maxcdn.bootstrapcdn./bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn./bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
<script src="https://ajax.googleapis./ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
        <div class="panel panel-default">
            <div class="panel-heading" role="tab" id="headingOne">
                <h4 class="panel-title">
                    <a class="collapsed accordion-toggle" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="false" aria-controls="collapseOne"> Header </a>
                </h4>
            </div>
            <div id="collapseOne" class="panel-collapse collapse in" role="tabpanel" aria-labelledby="headingOne">
                <div class="panel-body">
                    collapsible stuff
                </div>
            </div>
        </div>
    </div>

Update for Bootstrap 4:

Adding "show" causes it to be open by default.

<div class="collapse show" id="Mail">