You will need to install a user script manager extension to install this script.
The script hugely improves load speed of pages with lots of embedded Youtube videos by instantly showing clickable and immediately accessible placeholders, then the thumbnails are loaded in background.
You will only need this script on a few such sites (if at all), but by default the script runs everywhere, so you can manually limit it to those few sites: open the installed script in Tampermonkey/Violentmonkey editor and customize the include/exclude rules in the
Clickthe thumbnail to play the video in a standard Youtube embedded player with a full-screen button.
Shift-click to play as HTML5 video directly, 720p is automatically selected if available.
The behavior may be reversed by an option at the bottom right corner of any video thumbnail. The option is global and applies to all players.
Middle-click starts fullscreen playback.
Storyboard (aka "seekbar preview") is shown on mouseover at the bottom of the embedded videos. Click to start the video at the clicked time position.
Corner pinning buttons to pin a playing video in a page corner, so you can scroll the site and keep an eye on the video. Toggled in Options.
Drag'n'drop towards a page corner to start playing it there in a pinned state. Enabled if "Pinning" is enabled in Options.
There's also a link to open the video page on Youtube.
Last used volume is remembered for the native HTML5 player.
Video thumbnail is resized to fit available width or custom size, customizable in the right bottom corner of any processed video.
Other videos on current page are automatically paused when you click a new video and it starts to play.