page.html

<!DOCTYPE html>
<html>
<head>
  <title>Yt Fetch</title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous">
</head>
<body>
  <div class="mx-auto" style="width: 400px;">
    <form action="/fetches" method="post" class="mt-5">
      <div class="form-group">
        <label for="uuid" class="font-weight-bold">Enter ID of a YouTube channel</label>
        <input type="text" name="uuid" placeholder="(e.g. UCrDkAvwZum-UTjHmzDI2iIw)" class="form-control">
      </div>
      <input type="submit" value="Generate CSV" class="btn btn-primary">
    </form>
  </div>
</body>
</html>