JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrap">
    <div class="header">header</div>
    <div class="content">content</div>
    <div class="footer">footer</div>
</div>

CSS

body, html {
    width: 100%;
    height: 100%;
    margin:0;
    padding:0;
}
.wrap {
    height:100%;
    width:100%;
    display: -webkit-box;
    -webkit-box-orient: vertical;
    
    display: -moz-box;
    -moz-box-orient: vertical;
    
    display: box;
    box-orient: vertical;
}


.content {
    height:20px;
    width:100%;
    -webkit-box-flex: 1;
    -moz-box-flex: 1;
    box-flex: 1;
}
.header, .footer {
    background-color: gray;
    height: 20px;
    width: 100%;
    margin: 0;
    padding:5px;
}