Reduce initial-load page weight by only loading embedded video resources on-demand.
An on-demand embedded video in action:
Start with a link and thumbnail image, wrapped in a container with the video ID stored as a data attribute.
Style the placeholder image link as desired, including a custom play button. This setup also uses a technique for responsive embedded videos that scale with a custom aspect ratio.
Replace the image link with a normal embedded video <iframe> when the placeholder is clicked.
Responsive Embedded Videos
This technique works great when combined with mobile friendly, automatically-scaling embedded videos: