how to set div as tall as the browser code example

Example 1: how to set a div size to full screen

height: 100vh

Example 2: css window height

body, html {
  height: 100%;
}

#right {
  height: 100%;
}

Example 3: css set div heigtto screen

.left {
  height: 100vh;
  width: 50%;
  background-color: grey;
  float: left;
}

.right {
  height: 100vh;
  width: 50%;
  background-color: red;
  float: right;
}