JSFiddle - React, Tailwind, and code Playground

HTML

<input class="inputTxt" type="text" placeholder="Test" />

CSS

.inputTxt::-webkit-input-placeholder {
   text-transform: initial;
}

.inputTxt::-moz-placeholder { 
   text-transform: initial;
}

.inputTxt::-moz-placeholder {  
   text-transform: initial;
}

.inputTxt::-ms-input-placeholder { 
   text-transform: initial;
}

.inputTxt
{
    text-transform: uppercase;
}