Make YouTube and Vimeo Videos Responsive with CSS
.responsive-container {
position: relative;
padding-bottom: 56.25%;
padding-top: 30px;
height: 0;
overflow: hidden;
margin-bottom: 50px;
}
.responsive-container iframe {
position: absolute;
top: 0; left: 0;
width: 100%;
height: 100%;
}