Set div height equal to screen size

Using CSS {height: 100%;} matches the height of the parent. This could be anything, meaning smaller or bigger than the screen. Using {height: 100vh;} matches the height of the viewport.

.container {
    height: 100vh;
    overflow: auto;
}

According to Mozilla’s official documents, 1vh is:

Equal to 1% of the height of the viewport’s initial containing block.