Table of Contents

CSS - Background (Image)

About

The background of an element is the total size of the element:

Boxdim

When two element overlap, you can send one element to the background by setting the z-index

Properties

All properties that start with the prefix background are background properties.

background-image: url(flower.png), url(ball.png), url(grass.png);
background-position: center center, 20% 80%, top left, bottom right; 
background-origin: border-box, content-box;
background-repeat: no-repeat;
background-color: white
background-clip: border-box;
background-attachment: fixed;
background-size: cover; /* scale the background image proportionally so that its width and height are equal to, or greater than, the width/height of the element. */

More Documentation Reference - CSS Background 3

For a little bit the same property than background-size:

Demo

Background vs margin and padding

This demo helps to visualize the effect of margin and padding against the background limits with a light color against a dark color for the document.

You will see that only the margin has an effect on the background area.

.backgroundWithPadding {
    background-color: SkyBlue ;
    padding: 15px;
    border: 5px solid black;
}
.backgroundWithoutPadding {
    background-color: SkyBlue ;
    border: 5px solid black;
}
.backgroundWithPaddingAndMargin {
    background-color: SkyBlue ;
    border: 5px solid black;
    padding: 5px;
    margin: 10px;
}

body {
    background-color: steelblue;
}
<div class="backgroundWithPadding" >
light blue background With Padding and Without Margin
</div>
<div class="backgroundWithoutPadding" >
light blue background Without Padding and Without Margin
</div>
<div class="backgroundWithPaddingAndMargin " >
light blue background With Padding and Margin
</div>

The svg is used in an URL and should then be url encoded. (You can grab a background css directly via this codepen)

Svg Background Image

With the Url Data scheme

.navbar-toggler-icon {
   background-image: url("data:image/svg+xml,%3Csvg version='1.1' xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' width='17' height='17' viewBox='0 0 17 17'%3E%3Cg%3E%3C/g%3E%3Cpath d='M17 16v1h-17v-1h17zM12 10h2v5h1v-6h-4v6h1v-5zM7 7h2v8h1v-9h-4v9h1v-8zM2 3h2v12h1v-13h-4v13h1v-12z' fill='%23000000' /%3E%3C/svg%3E");
}

.navbar-toggler-icon {
    display: inline-block;
    width: 3em;
    height: 3em;
    vertical-align: middle;
    content: "";
    background-size: 100% 100%;
}
<span class="navbar-toggler-icon"></span>