HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>CSS required text :valid</title>
  <style>
    input:valid {
      border: 2px solid #15803d;
    }

    input:invalid {
      border: 2px solid #b91c1c;
    }
  </style>
</head>
<body>
  <form>
    <p><label>Name <input type="text" required value="Alex"></label></p>
    <p><label>Empty <input type="text" required></label></p>
  </form>
</body>
</html>

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CSS :valid - Required Text Field