Opacity & Transparency - Controlling Element Transparency

What is Opacity?

Opacity controls the transparency level of an entire element and its children. Values range from 0 (fully transparent) to 1 (fully opaque).

Opacity Property

Syntax:

opacity: value; /* 0 to 1 */

CSS Example:

.transparent {
    opacity: 0; /* Invisible */
}

.semi-transparent {
    opacity: 0.5; /* 50% transparent */
}

.opaque {
    opacity: 1; /* Fully visible (default) */
}

Opacity vs RGBA

opacity - Affects entire element

.box {
    opacity: 0.5; /* Everything inside is 50% transparent */
}

RGBA - Affects only background

.box {
    background-color: rgba(0, 123, 255, 0.5); /* Only background is transparent */
    color: black; /* Text stays fully opaque */
}

Common Patterns

Pattern 1: Hover Fade

.image {
    opacity: 1;
    transition: opacity 0.3s;
}

.image:hover {
    opacity: 0.7;
}

Pattern 2: Disabled State

.button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

Pattern 3: Overlay

.overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: black;
    opacity: 0.7;
}

Pattern 4: Fade In Animation

.fade-in {
    opacity: 0;
    animation: fadeIn 1s forwards;
}

@keyframes fadeIn {
    to {
        opacity: 1;
    }
}

Opacity & Transparency - Controlling Element Transparency

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