Box Shadow

18 MAY 2020

Box Shadow CSS Tutorial – How to Add a Drop Shadow to Any HTML Element

We can add a drop shadow to any HTML element using the CSS property box-shadow. Here's how.

Adding a Basic Drop Shadow

Let's first set up some basic HTML elements to add our drop shadows to:

<div id="box1" class="box">Box1</div>
<div id="box2" class="box">Box2</div>
<div id="box3" class="box">Box3</div>

Then add some basic CSS:

p {
    padding: 10px;
}
.box {
    padding: 20px;
    width: 50%;
    margin: 30px auto;
    background: #000;
    color: #fff;
}

The result is just three black boxes that will be easy for us to add drop shadows to by calling their unique id's:HTML elements setup

HTML elements setup

To add a basic drop shadow, let's use the box-shadow property on the Box 1:

/* offset-x | offset-y | color */
#box1 {
    box-shadow: 6px 12px yellow;
}

Adding a basic drop shadow to Box 1

We have 3 parameters here. The first 2 are, respectively, the x-offset and y-offset. They set the location of the drop shadow.

The offset is relative to the origin, which in HTML is always the top left corner of an element. A positive x-offset will move the shadow to the right, and a positive y-offset will move the shadow downwards.

The third parameter is the color of your drop shadow.

Keep in mind that although we used <div> elements here, the box-shadow property can be applied to any other HTML element as well.

Adding a Blur Radius

If we want the shadow to look a little more realistic, we will want to experiment with the blur-radius parameter.

This parameter controls how much to blur the shadow such that it becomes bigger and lighter. Let's apply it to Box 2:

/* offset-x | offset-y | blur-radius | color */
#box2 {
	box-shadow: 6px 12px 4px red;
}

Adding a blur radius to Box 2

The value of 4px sets the radius of the blur to apply to our drop shadow.

Adding a Spread Radius

If we want to control the size of the shadow, we can use the spread-radius parameter which controls how much a shadow grows or shrinks.

Let's add a spread radius of 8px to Box 2:

/* offset-x | offset-y | blur-radius | spread-radius | color */
#box2 {
    box-shadow: 6px 12px 4px 8px red;
}

Adding a spread radius in addition to a blur to Box 2

Adding a spread radius in addition to a blur to Box 2

Remember the order of these parameters!

Combining Multiple Shadows in a Single Property

If we want to get fancy, we can add multiple drop shadows to an element using a single box-shadow property.

Let's do that with Box 3 by simultaneously adding a blue and green drop shadow:

/* Any number of shadows, separated by commas */
#box3 {
    box-shadow: 6px 12px 2px 2px blue, -6px -12px 2px 2px green;
}

Adding multiple drop shadows to Box 3

combine multiple drop shadows

Bonus: Create an Inset Shadow

While it will not create a drop shadow, the inset parameter can also be used with the box-shadow property.

As the name suggests, this parameter creates an inset shadow (i.e. shadow inside a box).

The inset parameter can be placed either at the beginning or the end of the box-shadow property. Here we demonstrate its use with a blockquote element.

HTML:

<blockquote>
  <q>The key to success is to start before you're ready.</q>
  <p>&mdash; Marie Forleo</p>
</blockquote>

CSS:

blockquote {
  width: 50%;
  margin: 50px auto;
  padding: 20px;
  font-size: 24px;
  box-shadow: inset 10px 5px black;
}

Create an inset shadow

Of course you can add some blur and spread to enhance the shadow, or even multiple shadows:

 box-shadow: inset 10px 5px 25px 5px black, 5px 5px 12px 2px black;

Inset shadow combined with drop shadow

With the box-shadow property, we can easily make elements on a web page stand out to create a nice 3D lighting effect.

If you want to do some experimenting yourself, here's a code pen I created with the examples used in this tutorial.

Play around and see what you can come up with!

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Reference : https://www.freecodecamp.org/news/css-tutorial-drop-shadow/