.Docs

Opacity

Examples

100
75
60
50
25
<div class="opacity-100">100</div>
<div class="opacity-75">75</div>
<div class="opacity-60">60</div>
<div class="opacity-50">50</div>
<div class="opacity-25">25</div>;

Sass

Utilities API

Opacity Utilities produced from scss/components/bootstrap/_utilities.scss 

"opacity": (
    property: opacity,
    values: (
        0: 0,
        25: .25,
        50: .5,
        60: .6,
        75: .75,
        100: 1,
    )
),