required attribute not validating on dropdown list

Vote count:

0

for some reason, required attribute didnt work. where did i go wrong? I've already tried puting another <option> with blank value

<form action="">

    <select required>
    <optgroup label="test">
      <option value="">choose</option>
      <option value="red">red</option>
      <option value="yellow">yellow</option>
      <option value="green">green</option>
      <option value="grey">grey</option>
        </optgroup>

    </select>
    <input type="submit">
    </form>

asked 15 secs ago

phenomenon09

8

required attribute not validating on dropdown list