The border-image-outset CSS property sets the distance by which an element's border image is set out from its border box.

Portions of the border image that are rendered outside the border box as a result of this property do not trigger scrolling. Moreover, these areas don't capture mouse events.

Syntax

/* <length> value */
border-image-outset: 1rem;

/* <number> value */
border-image-outset: 1.5;

/* vertical | horizontal */
border-image-outset: 1 1.2;

/* top | horizontal | bottom */
border-image-outset: 30px 2 45px;

/* top | right | bottom | left */
border-image-outset: 7px 12px 14px 5px;

/* Global values */
border-image-outset: inherit;
border-image-outset: initial;
border-image-outset: unset;

The border-image-outset property may be specified as one, two, three, or four values. Each value is a <length> or <number>. Negative values are invalid.

  • When one value is specified, it applies the same outset to all four sides.
  • When two values are specified, the first outset applies to the top and bottom, the second to the left and right.
  • When three values are specified, the first outset applies to the top, the second to the left and right, the third to the bottom.
  • When four values are specified, the outsets apply to the top, right, bottom, and left in that order (clockwise).

Values

<length>
The size of the border outset as a dimension.
<number>
The size of the border outset as a multiple of the corresponding border-width.

Formal syntax

[ <length> | <number> ]{1,4}

Example

HTML

<div id="outset">This element has an outset border image!</div>

CSS

#outset {
  width: 10rem;
  background: #cef;
  border: 1.4rem solid;
  border-image: radial-gradient(#ff2, #55f) 40;
  border-image-outset: 1.5;  /* = 1.5 * 1.4rem = 2.1rem */
  margin: 2.1rem;
}

Result

Specifications

Specification Status Comment
CSS Backgrounds and Borders Module Level 3
The definition of 'border-image-outset' in that specification.
Candidate Recommendation Initial definition
Initial value0
Applies toall elements, except internal table elements when border-collapse is collapse. It also applies to ::first-letter.
Inheritedno
Mediavisual
Computed valueas specified, but with relative lengths converted into absolute lengths
Animation typediscrete
Canonical orderthe unique non-ambiguous order defined by the formal grammar

Browser compatibility

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DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung Internet
Basic supportChrome Full support 15Edge Full support 12Firefox Full support 15IE Full support 11Opera Full support 15Safari Full support 6WebView Android ? Chrome Android ? Edge Mobile Full support YesFirefox Android Full support 15Opera Android ? Safari iOS ? Samsung Internet Android ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown