css background video
<div class="fullscreen-bg">
<video loop muted autoplay poster="img/videoframe.jpg" class="fullscreen-bg__video">
<source src="video/big_buck_bunny.webm" type="video/webm">
<source src="video/big_buck_bunny.mp4" type="video/mp4">
<source src="video/big_buck_bunny.ogv" type="video/ogg">
</video>
</div>
<!-- CSS -->
.fullscreen-bg {
position: fixed;
top: 0;
right: 0;
bottom: 0;
left: 0;
overflow: hidden;
z-index: -100;
}
.fullscreen-bg__video {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}