background-size property was introduced in CSS3 for the purposes of setting the dimensions of a background image.
background-size property allows you to specify exactly what size your background image is. Furthermore, you can use the
contain keywords to scale the image to the box.
background-size property is used in conjunction with the
background-image property to define a background image on an HTML element.
In CSS3, the
background-size property has been added to the
background shorthand property. This means that you can set the
background-size from within the
background property (for example,
background: url("background.png") 40% / 10em lightblue round fixed border-box;).
The examples on this page include browser-specific properties that start with extensions such as
-moz-, etc. This is for browser compatibility reasons. See the bottom of this article for more on this.
The formal syntax for this property is:
For more information, see the Possible Values section below.
Note that this example includes various CSS extensions in addition to the W3C CSS3 property. This is for browser compatibility.
|Try it yourself!||
Here are the possible values:
|Applies to:||All elements|
|Animatable:||Yes, except keyword values|
At the time of writing, CSS3 was still under development and browser support for many CSS3 properties was limited or non-existent. For maximum browser compatibility many web developers add browser-specific properties by using extensions such as
-webkit- for Safari and Google Chrome,
-ms- for Internet Explorer,
-moz- for Firefox,
-o- for Opera etc. As with any CSS property, if a browser doesn't support a proprietary extension, it will simply ignore it.
This practice is not recommended by the W3C, however in many cases, the only way you can test a property is to include the CSS extension that is compatible with your browser.
Be aware that if you choose to use the proprietary CSS extensions in a live environment, your code will not pass any W3C CSS validation, as the browser-specific properties are not valid W3C properties.
Many of the CSS3 examples on this website include these browser specific properties. If they weren't included, most of the examples wouldn't work for most users (at least, not until possibly years after the article was written).
The major browser manufacturers are working to support the W3C properties, and eventually, you will be able to omit these browser-specific properties.