<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
body {
background: red;
height: 5000px;
}
.container {
background: rgba(0, 0, 0, 0.534);
width: 100%;
/* height: 100vh; */
height: 100%;
}
</style>
</head>
<body>
<div class="container">
</div>
</body>
</html>
vh means the viewport height, and 100% means 100%.
Learn about lvh, svh , dvh