JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
  background-color: #000;
  width: calc(100px * var(--px));
  height: calc(100px * var(--px));
}

JavaScript

let pixelRatioBox = document.querySelector(".pixel-ratio");

const updatePixelRatio = () => {
  document.documentElement.style.setProperty('--px', 1/devicePixelRatio);
  matchMedia(`(resolution: ${devicePixelRatio}dppx)`).addEventListener("change", updatePixelRatio, { once: true })
}

updatePixelRatio();