Have a child opacity different then parent opacity with CSS

Question

Here are my box classes

.rectangle-box {
    width: 200px;
    height: 30px;
    background: #808080;
    opacity: 0.3;
    float: right;
}

.re         


        

Answer 1

Use RGBA instead of hex. using opacity: affects child elements and rgba does not

.rectangle-box {
        width: 200px;
        height: 30px;
        background-color: rgba(128,128,128, 0.3);
        float: right;

    }

    .rectangle-red {
        width: 65px;
        height: 30px;
        background-color: rgba(255,71,66, 1);
      float: left;
    } 

Answer 2

you can't

All you can do is create element inside .rectangle-box absolute (my case) or relative or whatever you want with lower opacity .lower-opacityso they are siblings and not disturb each other opacity property

.rectangle-box {
    width: 200px;
    height: 30px;
    float: right;
    position: relative;
}
.lower-opacity{
    position: absolute;
    opacity: 0.3;
    width: 100%;
    height: 100%;
    background: #808080; //**EDITED** BACKGROUND NOW WILL BE TRANSPARENT
}
.rectangle-red {
    width: 65px;
    height: 30px;
    background: #ff4742;
    opacity: 1;
    float: left;
}


<div class="rectangle-box">
    <div class="lower-opacity"></div>
    <div class="rectangle-red"></div>
</div>

Answer 3

You can't the opacity cannot be greater than parent

but you can use two methods

I have used rgba rgba(0,0,0,0.0)

.rectangle-box {
  width: 200px;
  height: 30px;
  background: rgba(128, 128, 128, 0.3);
  float: right;
  position: relative;
}

.rectangle-red {
  width: 65px;
  height: 30px;
  background: #ff4742;
  opacity: 1;
  float: left;
}

<div class="rectangle-box">
  <div class="rectangle-red"></div>
</div>

Or the second method i have used :pseudo element to add a background

.rectangle-box {
  width: 200px;
  height: 30px;
  float: right;
  position: relative;
}

.rectangle-box:after {
  content: '';
  opacity: 0.3;
  background: #808080;
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  top: 0;
  z-index:-1;
}

.rectangle-red {
  width: 65px;
  height: 30px;
  background: #ff4742;
  opacity: 1;
  float: left;
}

<div class="rectangle-box">
  <div class="rectangle-red"></div>
</div>

Answer 4

A better way to structure this would be to create a div that contains both boxes. This way each of the boxes opacity will not interfere with each other.

<div class="container">
    <div class="rectangle-box"></div>
    <div class="rectangle-red"></div>
</div>

.container{
    width: 200px;
    height: 30px;
    float: right;
}
.rectangle-box {
    width: 100%;
    height: 100%;
    background: #808080;
    opacity: 0.3;
}

.rectangle-red {
    width: 65px;
    height: 100%;
    background: #ff4742;
    opacity: 1;
    float: left;
}

Answer 5

Here is a nice and neat way using pseudo elements.

With this you can as well add images and svg to each background which gives a lot of options.

If you need other elements within each box, you'll need the second inner div.

.rectangle-box {
  width: 200px;
  height: 30px;
  float: right;
  position: relative;
}

.rectangle-box:before {
  content: "";
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  position: absolute;
  background: #808080;
  opacity: 0.3;
}
.rectangle-box:after {
  content: "";
  top: 0;
  left: 0;
  width: 65px;
  height: 100%;
  position: absolute;
  background: #ff4742;
  opacity: 1;
}

<div class="rectangle-box">
</div>