JSFiddle - React, Tailwind, and code Playground

HTML

<div class="modal_overlay">
    <div class="modal">content</div>
</div>

CSS

.modal_overlay{
    width: 100%;
    height: 100%;
    position: fixed;
    text-align: center;
    background: rgba(0, 0, 0, 0.8);
    top: 0;
    left: 0;
    z-index: 9;
    justify-content: center;
    align-items: center;
    display: flex;
    overflow: auto;
}

.modal{
    z-index: 10;
    display: block;
    background: #fff;
    min-width: 500px;
    min-height: 300px;
}