Background overlay
<!DOCTYPE html>
<html>
<head>
<title>BACKGROUND OVERLAY | par NGLESSON</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="keyword" content="BACKGROUND OVERLAY">
<meta name="author" content="Mezgani said">
<meta name="copyright" content="NGLESSON">
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<link href="style.css" rel="stylesheet">
</head>
<body>
<div class="overlay"></div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="script.js"></script>
</body>
</html>
body {
background: url("../../assets/imgs/forcode/bkpage3.jpg") no-repeat center center fixed;
background-size: cover;
width: 100%;
min-height: 100vh;
}
.overlay {
width: 100%;
height: 100%;
position: absolute;
z-index: -1;
top: 0;
left: 0;
background: rgba(0, 0, 0, 0.45);
}