JSFiddle - React, Tailwind, and code Playground

HTML

<h1>Checks if you are in incognito mode</h1>
<div id="result"></div>

JavaScript 1.7

async function main() {
  if ('storage' in navigator && 'estimate' in navigator.storage) {
      const {usage, quota} = await navigator.storage.estimate();
      console.log(`Using ${usage} out of ${quota} bytes.`);

      if(quota < 120000000){
        result.textContent = "it seems like you are in incognito mode";
      } else {
        result.textContent = "it does not seem like you are in incognito mode";
      }   
  } else {
      result.textContent = "check failed?";
  }
}
main();