JSFiddle - React, Tailwind, and code Playground

HTML

<label for="subdomain">Subdomain:</label>
<input type="text" placeholder="ExampleDomain" id="subdomain" />
<input type="text" id="subdomaintwo" value=".domain.com" disabled/>

CSS

input[type="text"]#subdomaintwo{
    -webkit-appearance:none!important;
    color:red;
    text-align:right;
    width:75px;
    border:1px solid gray;
    border-left:0px;
    margin:0 0 0 -7px;
    background:white;
}
input[type="text"]#subdomain{
    -webkit-appearance:none!important;
    border:1px solid gray;
    border-right:0px;
    outline:none;
}