<iframe width="1381" height="480" src="https://www.youtube.com/embed/" frameborder="0" class="embed-responsive-item" src="" id="video" allowscriptaccess="always" code example

Example: embed-responsive-item

<div class="embed-responsive embed-responsive-16by9">
  <iframe class="embed-responsive-item" src="https://www.youtube.com/embed/zpOULjyy-n8?rel=0" allowfullscreen></iframe>
</div>