I think you need to change the CSS on your video element. Remove the max-width: 100% and set the height to height: 100vh;. It will crop the edges of the video on smaller screens, but that can’t be helped if you want it to be full screen height.
@Owen, There are several ways to do it. First: You can do it from Backend. Create a page “home” and add the video from Media button and Choose this page as “Home” from Setting -> Reading –> Static Page Second: You can create a home page template and put the video Url path in that … Read more
So, you want auto play or not? I think in any case these it might be useful: https://codepen.io/dudleystorey/pen/PZyMrd
I don’t think there is a need to override any core files. You can just use javascript to stop autoplaying the video. I tested the following code on Twenty Seventeen theme and it works fine. For example: $( document ).ready( function() { $( document ).on( ‘wp-custom-header-video-loaded’, function() { $(“#wp-custom-header-video”).attr(‘autoplay’,false); }); }); This does the trick.