The background-size
CSS property makes it possible to adjust the width and height of background images, thus overriding the default behavior which tiles background images at their full size. You can scale the image upward or downward as desired.
Let's consider a large image, a 2982x2808 Firefox logo image. We want (for some reason likely involving horrifyingly bad site design) 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.
<div class="tiledBackground"> </div>
.tiledBackground { background-image: url(https://mdn.mozillademos.org/files/8971/firefox_logo.png); background-size: 150px; width: 300px; height: 300px; border: 2px solid; color: pink; }
You can also specify both the horizontal and vertical sizes of the image, like this:
background-size: 300px 150px;
The result looks like this:
On the other end of the spectrum, you can scale an image up in the background. Here we scale a 32x32 pixel favicon to 300x300 pixels:
.square2 { background-image: url(favicon.png); background-size: 300px; width: 300px; height: 300px; border: 2px solid; text-shadow: white 0px 0px 2px; font-size: 16px; }
As you can see, the CSS is actually essentially identical, save the name of the image file.
Besides <length>
values, the background-size
CSS property offers two special size values, contain
and cover
. Let's take a look at these.
contain
The contain
value specifies that, regardless of the size of the containing box, the background image should be scaled so that each side is as large as possible while not exceeding the length of the corresponding side of the container. Try resizing the example below to see this in action.
<div class="bgSizeContain"> <p>Try resizing this element!</p> </div>
.bgSizeContain { background-image: url(https://mdn.mozillademos.org/files/8971/firefox_logo.png); background-size: contain; width: 160px; height: 160px; border: 2px solid; color: pink; resize: both; overflow: scroll; }
cover
The cover
value specifies that the background image should be sized so that it is as small as possible while ensuring that both dimensions are greater than or equal to the corresponding size of the container. Try resizing the example below to see this in action.
<div class="bgSizeCover"> <p>Try resizing this element!</p> </div>
.bgSizeCover { background-image: url(https://mdn.mozillademos.org/files/8971/firefox_logo.png); background-size: cover; width: 160px; height: 160px; border: 2px solid; color: pink; resize: both; overflow: scroll; }
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https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Backgrounds_and_Borders/Scaling_background_images