CSS — Opacity

Opacity controls how transparent or visible an element is. It can be set between 0 and 1, where 0 makes the element completely invisible and 1 makes it fully visible. This is useful for creating fade effects or making certain elements like overlays partially see-through. For example, an image with opacity: 0.5 will look faded while still being visible. You can combine opacity with hover effects to make smooth transitions and animations.

.overlay { opacity: 0.5; }