This property is a shorthand for the following CSS properties:

• background-attachment
• background-clip
• background-color
• background-image
• background-origin
• background-position
• background-repeat
• background-size

/* Using a <background-color> */
background: green;

/* Using a <bg-image> and <repeat-style> */
background: url("test.jpg") repeat-y;

/* Using a <box> and <background-color> */
background: border-box red;

/* A single image, centered and scaled */
background: no-repeat center/80% url("../img/image.png");

/* Global values */
background: inherit;
background: initial;
background: revert;
background: revert-layer;
background: unset;

The background property is specified as one or more background layers, separated by commas.

The syntax of each layer is as follows:

• Each layer may include zero or one occurrences of any of the following values:
  • <attachment>
  • <bg-image>
  • <position>
  • <bg-size>
  • <repeat-style>
• The <bg-size> value may only be included immediately after <position>, separated with the '/' character, like this: "center/80%".
• The <box> value may be included zero, one, or two times. If included once, it sets both background-origin and background-clip. If it is included twice, the first occurrence sets background-origin, and the second sets background-clip.
• The <background-color> value may only be included in the last layer specified.

<attachment>

See background-attachment. Default: scroll.

<box>

See background-clip and background-origin. Default: border-box and padding-box respectively.

<background-color>

See background-color. Default: transparent.

<bg-image>

See background-image. Default: none.

<position>

See background-position. Default: 0% 0%.

<repeat-style>

See background-repeat. Default: repeat.

<bg-size>

See background-size. Default: auto.

The following three lines of CSS are equivalent:

background: none;
background: transparent;
background: repeat scroll 0% 0% / auto padding-box border-box none transparent;

Browsers do not provide any special information on background images to assistive technology. This is important primarily for screen readers, as a screen reader will not announce its presence and therefore convey nothing to its users. If the image contains information critical to understanding the page's overall purpose, it is better to describe it semantically in the document.

• MDN Understanding WCAG, Guideline 1.1 explanations
• Understanding Success Criterion 1.1.1 | W3C Understanding WCAG 2.0

background = 
  [ <bg-layer># , ]? <final-bg-layer>  

<bg-layer> = 
  <bg-image>                      ||
  <bg-position> [ / <bg-size> ]?  ||
  <repeat-style>                  ||
  <attachment>                    ||
  <box>                           ||
  <box>                           

<final-bg-layer> = 
  <'background-color'>            ||
  <bg-image>                      ||
  <bg-position> [ / <bg-size> ]?  ||
  <repeat-style>                  ||
  <attachment>                    ||
  <box>                           ||
  <box>                           

<bg-image> = 
  <image>  |
  none     

<bg-position> = 
  [ left | center | right | top | bottom | <length-percentage> ]  |
  [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ]  |
  [ center | [ left | right ] <length-percentage>? ] && [ center | [ top | bottom ] <length-percentage>? ]  

<bg-size> = 
  [ <length-percentage [0,∞]> | auto ]{1,2}  |
  cover                                      |
  contain                                    

<repeat-style> = 
  repeat-x                                     |
  repeat-y                                     |
  [ repeat | space | round | no-repeat ]{1,2}  

<attachment> = 
  scroll  |
  fixed   |
  local   

<box> = 
  border-box   |
  padding-box  |
  content-box  

<image> = 
  <url>       |
  <gradient>  

<length-percentage> = 
  <length>      |
  <percentage>  

<url> = 
  url( <string> <url-modifier>* )  |
  src( <string> <url-modifier>* )  

HTML

<p class="topbanner">
  Starry sky<br />
  Twinkle twinkle<br />
  Starry sky
</p>
<p class="warning">Here is a paragraph</p>
<p></p>

CSS

.warning {
  background: pink;
}

.topbanner {
  background: url("starsolid.gif") #99f repeat-y fixed;
}

Result

• box-decoration-break
• Using gradients
• Using multiple backgrounds