CSS border-radius

The CSS border-radius property is a shorthand property for setting multiple "border radius" related properties in one place. This is an efficient way of adding rounded corners to your borders.

The border-radius property sets the border-top-left-radius, border-top-right-radius, border-bottom-left-radius, and border-bottom-right-radius properties.

The border-radius property can be used in conjunction with the border property (or another border-related property) in order to set the actual border, however, it can also be used without explicitly setting those properties. For example, if you've set a background color for the element, the background color will be rounded at the corners (even if you don't explictly set a border property).

Note that order is important. You must specify the values in the same order as listed in the Possible Values section below.

Syntax

border-radius: radius

Or:

border-radius: horizontal-radius / vertical-radius

See below for a more detailed explanation of the accepted values.

Possible Values

Values/Syntax

The possible values for this property are:

[ <length> | <percentage> ]{1,4} [ / [ <length> | <percentage> ]{1,4} ]?

Explanation of the Values

<length>
Specifies the radius using a fixed length, for example, 10px.
<percentage>
Specifies the radius using a percentage value, for example, 10%.

Explanation of the Syntax

You can provide between one and eight values. Here's an explanation:

  • If you provide only one value, it will determine the radius of all four corners - both the horizontal radius and the vertical radius.
  • The values must be provided in the following order: top-left, top-right, bottom-right, and bottom-left. If the value for bottom-left is omitted it will be the same as the value for top-right. If the value for bottom-right is omitted it will be the same as the value for top-left. If top-right is omitted it will be the same as top-left.
  • To set a different radius for horizontal vs vertical, use a forward-slash to separate them ( / ). The values on the left side of the forward-slash determine the horizontal radius. The values on the right side of the forward-slash determine the vertical radius. Up to four values per side are accepted (i.e. one for each corner).

In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:

initial
Represents the value specified as the property's initial value.
inherit
Represents the computed value of the property on the element's parent.
unset
This value acts as either inherit or initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.

Basic Property Information

Initial Value
See individual properties
Applies To
All elements
Inherited?
No
Media
Visual
Animatable
Yes (see example)

Example Code

Basic CSS

border-radius: 8px;

Working Example within an HTML Document

<!doctype html>
<title>Example</title>
<style>
.rounded-border {
  width: 200px;
  padding: 30px;
  border: 1px solid crimson;
  border-radius: 35px 10px / 20px 10px;
}
</style>
<div class="rounded-border">
  This box has rounded borders.
</div>

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CSS Specifications

Browser Support

The following table provided by Caniuse.com shows the level of browser support for this feature.

Vendor Prefixes

For maximum browser compatibility many web developers add browser-specific properties by using extensions such as -webkit- for Safari, Google Chrome, and Opera (newer versions), -ms- for Internet Explorer, -moz- for Firefox, -o- for older versions of 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.

The major browser manufacturers generally strive to adhere to the W3C specifications, and when they support a non-prefixed property, they typically remove the prefixed version. Also, W3C advises vendors to remove their prefixes for properties that reach Candidate Recommendation status.

Many developers use Autoprefixer, which is a postprocessor for CSS. Autoprefixer automatically adds vendor prefixes to your CSS so that you don't need to. It also removes old, unnecessary prefixes from your CSS.

You can also use Autoprefixer with preprocessors such as Less and Sass.