CSS, Responsive | Type: JavascriptResponsive Tabs to Accordian

At chosen break point, tabs become an accordian.

HTML
<ul class="tabs">
    <li class="active">Tab 1</li>
    <li>Tab 2</li>
    <li>Tab 3</li>
</ul>

<div class="tab_container">
    <h3 class="d_active tab_drawer_heading">Tab 1</h3>
    <div id="tab1" class="tab_content">
        <h2>Tab 1 content</h2>
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec ac metus augue.</p>
    </div> <!-- #tab1 -->

    <h3 class="tab_drawer_heading">Tab 2</h3>
    <div id="tab2" class="tab_content">
        <h2>Tab 2 content</h2>
        <p>Nunc dui velit, scelerisque eu placerat volutpat, dapibus eu nisi. Vivamus eleifend vestibulum odio non vulputate.</p>
    </div>< <!-- #tab2 -->

    <h3 class="tab_drawer_heading">Tab 3</h3>
    <div id="tab3" class="tab_content">
        <h2>Tab 3 content</h2>
        <p>Nulla eleifend felis vitae velit tristique imperdiet. Etiam nec imperdiet elit. Pellentesque sem lorem, scelerisque sed facilisis sed, vestibulum sit amet eros.</p>
    </div> <!-- #tab3 -->
</div> <!-- .tab_container -->


CSS
ul.tabs {
    margin: 0;
    padding: 0;
    float: left;
    list-style: none;
    height: 32px;
    border-bottom: 1px solid #333;
    width: 100%;
}

ul.tabs li {
    float: left;
    margin: 0;
    cursor: pointer;
    padding: 0;
    width:32%;
    text-align:center;
    margin-right:2%;
    height: 31px;
    line-height: 31px;
    border-radius:6px 6px 0 0;
    background-color: #666;
    color: #ccc;
    overflow: hidden;
    position: relative;
}

.tab_last { margin-right:0!important; float:right!important;}

ul.tabs li:hover {
    background-color: #ccc;
    color: #333;
}

ul.tabs li.active {
    background-color: #ddd;
    color: #333;
    border-bottom: 1px solid #fff;
    display: block;
}

.tab_container {
    border: 1px solid #333;
    border-top: none;
    clear: both;
    float: left;
    width: 100%;
    background: #fff;
    overflow: auto;
}

.tab_content {
    padding: 20px;
    display: none;
}

.tab_drawer_heading { display: none; }

@media screen and (max-width: 480px) {
    .tabs {
        display: none;
    }
    .tab_drawer_heading {
        display: block;
        background-color: #ccc;
        color: #fff;
        border-top: 1px solid #333;
        margin: 0;
        padding: 5px 20px;
        cursor: pointer;
        -webkit-touch-callout: none;
        -webkit-user-select: none;
        -khtml-user-select: none;
        -moz-user-select: none;
        -ms-user-select: none;
        user-select: none;
     }
     .d_active {
        background-color: #666;
        color: #fff;
     }
}


JAVASCRIPT
// tabbed content
// http://www.entheosweb.com/tutorials/css/tabs.asp
$(".tab_content").hide();
$(".tab_content:first").show();

/* if in tab mode */
$("ul.tabs li").click(function() {
    $(".tab_content").hide();
    var activeTab = $(this).attr("rel");
    $("#"+activeTab).fadeIn();
    $("ul.tabs li").removeClass("active");
    $(this).addClass("active");
    $(".tab_drawer_heading").removeClass("d_active");
    $(".tab_drawer_heading[rel^='"+activeTab+"']").addClass("d_active");
});

/* if in drawer mode */
$(".tab_drawer_heading").click(function() {
    $(".tab_content").hide();
    var d_activeTab = $(this).attr("rel");
    $("#"+d_activeTab).fadeIn();
    $(".tab_drawer_heading").removeClass("d_active");
    $(this).addClass("d_active");
    $("ul.tabs li").removeClass("active");
    $("ul.tabs li[rel^='"+d_activeTab+"']").addClass("active");
});

/* Extra class "tab_last" to add border to right side of last tab */
    $('ul.tabs li').last().addClass("tab_last");

Reference Links

https://codepen.io/kazmeyer/pen/lzqhf