javascript - position fixed; height 100 is set but it is not the width and height of the browser's visible window. Please clarify.

Question

The following css style code is set, but the displayed height is not full screen, as shown in the figure.

.ss_hide{
    position: fixed;
    background: rgba(0,0,0,.2);
    height: 100%;
    width: 100%;
}

Answer 1

Recommended to use in full screen

top: 0;
bottom: 0;
left: 0;
right: 0;

Answer 2

Check whether the size of your body and html are full screen. Or 100vh high and 100vw wide

Answer 3

You must also add top:0;left:0;

Answer 4

Absolute positioning is out of the document flow, right? Since everything is absolutely positioned top:0;left:0;right:0;bottom:0; just covers the screen