If I wanted to embed 20 videos on a page will they all start buffering on page load or will they wait until they are played/interacted with for the first time? If they buffer on load how could I circumvent this until I want to display the video? I don't want a user to be buffering 20 videos when they may only be watching one or even none at all.
You are looking at the preload attribute of HTML5 video tag. Here is the doc. Basically there are three options :
auto - when browser should load the entire video when the page loads
metadata - when browser should load only metadata when the page loads
none - when browser should NOT load the video when the page loads
来源：https://stackoverflow.com/questions/21790012/do-html-5-videos-buffer-on-page-load-or-only-when-playing-the-video