With Bootstrap Opacity, you can control the opacity level of an element. Predefined Bootstrap Opacity values are, 100% (opacity-100) 75% (opacity-75) 50% (opacity-50) 25% (opacity-25) 0 (opacity-0) - Completely transparent The Opacity is used to adjust the transparency level (visibility) of an element. Let's look into an example, See the Pen Bootstrap Opacity by Prime Study Hub ( @PrimeStudyHub ) on CodePen .