In the age of dynamic and interactive content, now or then we need to show playing media on web pages. The media should be compatible with all the devices across all the browsers i.e. responsive according the page layout rendering in the device (Phone, Tablet, Laptop or Desktop).
Lets see the below article to know how to achieve the responsiveness of youtube video in simple step using just HTML and CSS.
Source: Responsive YouTube videos to scale in all browsers, ipads, iPhones and tablets