The following video is from the post Responsive Images using <picture> and srcset/sizes – by Matt Steele
Big heavy images are responsible for most of the bloat on a responsive website, but it doesn’t have to be that way. Here’s the latest HTML elements you can use to keep your images small, and your site lean & fast. – Matt Steele
Reference: Srcset and sizes
Adeline Yaw - Happiness Engineer @ Automattic 