index.html

<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="icon" type="image/svg+xml" href="favicon.svg" />
  <title>Devtools Detecter</title>
  <meta name="description" content="Devtools Detecter">
  <meta name="keywords" content="DevTools,detecter">
</head>

<body>
  <script type="module">
    import DevtoolsDetecter from "./index.js"
    DevtoolsDetecter.debug()
    DevtoolsDetecter.addListener(isOpen => {
      if (isOpen) {
        document.title = "DevTools detected";
        document.body.style["backgroundColor"] = "red";
      } else {
        document.title = "DevTools NOT detected";
        document.body.style["backgroundColor"] = "unset";
      }
    })
    DevtoolsDetecter.launch()
  </script>
</body>

</html>