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

The parts of the border image that are rendered outside the element's border box with border-image-outset do not trigger overflow scrollbars and don't capture mouse events.


/* <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 and will cause the border-image-outset declaration to be ignored.

  1. If one value is specified, it applies to all four sides.
  2. If two values are specified, the first applies to the top and bottom and the second to the left and right.
  3. If three values are specified, the first applies to the top, the second to the left and right, and the third to the bottom.
  4. If four values are specified, they apply to the top, right, bottom, and left in that order (clockwise).


The size of the border-image outset as a dimension — a number with a unit.
The size of the border-image outset as a multiple of the element's corresponding border-widths. For example, if an element has border-width: 1em 2px 0 1.5rem, and border-image-outset: 2, the final border-image-outset would be calculated as 2em 4px 0 3rem.

Formal definition

Initial value 0
Applies to all elements, except internal table elements when border-collapse is collapse. It also applies to ::first-letter.
Inherited no
Computed value as specified, but with relative lengths converted into absolute lengths
Animation type by computed value type

Formal syntax

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


Outsetting a border image


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


#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;



Specification Status Comment
CSS Backgrounds and Borders Module Level 3
The definition of 'border-image-outset' in that specification.
Candidate Recommendation Initial definition

Browser compatibilityUpdate compatibility data on GitHub

Chrome Edge Firefox Internet Explorer Opera Safari
border-image-outset 15 12 15 11 15 6
Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet
border-image-outset ≤37 18 15 14 6 1.0

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