<!DOCTYPE html>

<html>
<head>
    <style>
        .box {
          width: 300px;
          height: 300px;
          background-color: blue;
        }
        
        .clipped {
            -webkit-clip-path: inset(0 50px);
            -webkit-mask: linear-gradient(transparent, black);
        }
    </style>
</head>
<body>
    <div class="clipped box"></div>
</body>
</html>