Css Background Opacity

Controlled opacity with RGBA

Utilizing ::before for semi-transparent backgrounds

In the world of CSS, ::before pseudo-element is your designer Swiss army knife to achieve semi-transparent designs. Let's see how it works:

.container {
  position: relative;
}

.container::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  width: 100%;
  background-color: rgba(0, 0, 0, 0.5); /* The ghostly veil */
  z-index: -1; /* Won't block our readable text */
}
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This crafty trick applies an adjustable 'veil' behind the text, ensuring that your content stays sharp as cheddar!

Coping with IE8

We also need to think about our friends on legacy browsers, such as IE8. It can handle a transparent PNG or the filter property with rgba:

.transparent-bg {
  background: url('/path/to/transparent-bg.png');
  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#4Cffffff, endColorstr=#4Cffffff); /* wordiest. filter. ever. */
}
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While it's not the quickest to type, this solution achieves transparency and compatibility.

Sass for the win

In Sass, the transparentize function allows you to precisely dial-in your desired opacity:

.transparent-bg {
  background-color: transparentize($color, 0.7); // 30% opacity, because we can
}
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Clear child text and full-screen layers

Preserving child clarity

To avoid ghostly texts, ensure filter property of child elements is set to none:

.child {
  filter: none; /* Because kids don't need filters */
}
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Use zoom for any element that doesn't comply to filter rules.

Stretching the full-screen

For full-screen coverage, apply absolute positioning with zero positioning details:

.fullscreen::before {
  position: absolute;
  top: 0; 
  left: 0; 
  bottom: 0; 
  right: 0;
  /* The rest of your spooky styles here */
}
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