JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
   <div class="fix">fix</div>
</div>

CSS

.wrapper {
        max-width: 500px;
        border: 1px solid red;
        height: 5500px;
        position: relative;
    }
        
        
    .fix {
        max-width: inherit;
        width: 100%;
        height: 20px;
        position:fixed;
        background: black;
    }