JSFiddle - React, Tailwind, and code Playground

HTML

<div id="footer" style="border:4px solid black;"></div>
<div id="content" style="border:4px solid blue;">
    just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />jujust a line here<br />jujust a line here<br />st a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />st a line here<br />jusjust a line here<br />just a line here<br />just a line here<br />just a line here<br />t a line here<br />jusjust a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />just a line here<br />t a line here<br />
</div>

CSS

html
{
    height:100%; 
    max-height:100%;  
    padding:0; 
    margin:0; 
}
body
{
    height:100%;
    max-height:100%;
    margin:0;
    border:0;
    }
            
#content
{
    display:block;
    height:100%;
    bottom:170px;
    overflow:auto;
    position:relative;
}
    
#footer
{
    position:fixed;
    margin:0;
    bottom:-1px;
    right:0px;
    display:block;
    width:100%;
    height:120px;
}

* html #footer
{
    position:absolute;
}