index.html

<!DOCTYPE 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">
  <meta name="description"
      content="Its a Custom Modal built with pure Javascript">
  <meta name="robots" content="index, follow">
  <meta name="keywords" content="javascript, modal js, javascript custom modal popup, custom modal, modal with Javascript">
  <meta name="author" content="Tarun Mandal Ghosh">
    <link rel="stylesheet" href="style.css">
    <script src="script.js" defer></script>
    <title>Modal With JS</title>
</head>
<body>
    <button id="open">Open Modal</button>

    <div id="overlay"></div>
    <div id="modal">
        <h1>This is Modal</h1>
        <button id="close">Close Modal</button>
    </div>
</body>
</html>