css properties background-size

The background-size CSS property sets the size of the element's background image. The image can be left to its natural size, stretched, or constrained to fit the available space.

Spaces not covered by a background image are filled with the background-color property, and the background color will be visible behind background images that have transparency/translucency.

Syntax

/* Keyword values */
background-size: cover;
background-size: contain;

/* One-value syntax */
/* the width of the image (height becomes 'auto') */
background-size: 50%;
background-size: 3.2em;
background-size: 12px;
background-size: auto;

/* Two-value syntax */
/* first value: width of the image, second value: height */
background-size: 50% auto;
background-size: 3em 25%;
background-size: auto 6px;
background-size: auto auto;

/* Multiple backgrounds */
background-size: auto, auto; /* Not to be confused with `auto auto` */
background-size: 50%, 25%, 25%;
background-size: 6px, auto, contain;

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

The background-size property is specified in one of the following ways:

To specify the size of multiple background images, separate the value for each one with a comma.

Values

contain

Scales the image as large as possible within its container without cropping or stretching the image. If the container is larger than the image, this will result in image tiling, unless the background-repeat property is set to no-repeat.

cover

Scales the image (while preserving its ratio) to the smallest possible size to fill the container (that is: both its height and width completely cover the container), leaving no empty space. If the proportions of the background differ from the element, the image is cropped either vertically or horizontally.

auto

Scales the background image in the corresponding direction such that its intrinsic proportions are maintained.

<length>

Stretches the image in the corresponding dimension to the specified length. Negative values are not allowed.

<percentage>

Stretches the image in the corresponding dimension to the specified percentage of the background positioning area. The background positioning area is determined by the value of background-origin (by default, the padding box). However, if the background's background-attachment value is fixed, the positioning area is instead the entire viewport. Negative values are not allowed.

Intrinsic dimensions and proportions

The computation of values depends on the image's intrinsic dimensions (width and height) and intrinsic proportions (width-to-height ratio). These attributes are as follows:

Note: In Gecko, background images created using the element() function are currently treated as images with the dimensions of the element, or of the background positioning area if the element is SVG, with the corresponding intrinsic proportion. This is non-standard behavior.

Based on the intrinsic dimensions and proportions, the rendered size of the background image is computed as follows:

Note: Background sizing for vector images that lack intrinsic dimensions or proportions is not yet fully implemented in all browsers. Be careful about relying on the behavior described above, and test in multiple browsers to be sure the results are acceptable.

Formal definition

Initial valueauto
Applies toall elements
Inheritedno
Computed valuelist, each item a pair of sizes (one per axis) each represented as either a keyword or a computed <length-percentage> value
Animation typerepeatable list

Formal syntax

<bg-size>#

Examples

Tiling a large image

Let's consider a large image, a 2982x2808 Firefox logo image. We want to tile four copies of this image into a 300x300-pixel element. To do this, we can use a fixed background-size value of 150 pixels.

HTML

<div class="tiledBackground"></div>

CSS

.tiledBackground {
  background-image: url(https://www.mozilla.org/media/img/logos/firefox/logo-quantum.9c5e96634f92.png);
  background-size: 150px;
  width: 300px;
  height: 300px;
  border: 2px solid;
  color: pink;
}

Result

See Resizing background images for more examples.

See also