css backgroundcolor with opacity code example

Example 1: css opacity background color

background: rgba(255, 255, 255, 0.25);

Example 2: background color with opacity

h1 {background-color:rgba(255,0,0,0.3);}

Example 3: background opacity css hex

background-color: #ff000088; <--- the 88 is the alpha
background-color: #ff0000 50%;