JSFiddle - React, Tailwind, and code Playground

HTML

<div class="fixed">
    <div class="center"></div>
</div>

CSS

.fixed {
    width:100%;
    height:40px;
    background:yellow;
    position:fixed;
    bottom:0;
}
.center {
    margin:0 auto;
    width: 50%;
    height:inherit;
    background:red;
}