SVG is the new era, nowadays with all these super-pixel-dense devices our poor jpg and png images are getting stretched, scaled, distorted all over and they render badly causing some bad-looking effects. This is why they are all being replaced with more modern, flexible SVGs.

The key to creating a responsive YouTube embed is with padding and a container element, which allows you to give it a fixed aspect ratio. You can also use this technique with most other iframe-based embeds, such as slideshows.

Responsive Equal Height Divs