Video 100% width and height

If you're looking for the equivalent to background-size: cover for video.

video {
  object-fit: cover;
}

This will fill the container without distorting the video.

---

^{PS: I'm extending on Leo Yu's answer here.}

By checking other answers, I used object-fit in CSS:

video {
    object-fit: fill;
}

From MDN (https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit):

The object-fit CSS property specifies how the contents of a replaced element should be fitted to the box established by its used height and width.

Value: fill

The replaced content is sized to fill the element’s content box: the object’s concrete object size is the element’s used width and height.