border-image-width

If this property's value is greater than the element's border-width, the border image will extend beyond the padding (and/or content) edge.

/* Keyword value */
border-image-width: auto;

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

/* <percentage> value */
border-image-width: 25%;

/* <number> value */
border-image-width: 3;

/* vertical | horizontal */
border-image-width: 2em 3em;

/* top | horizontal | bottom */
border-image-width: 5% 15% 10%;

/* top | right | bottom | left */
border-image-width: 5% 2em 10% auto;

/* Global values */
border-image-width: inherit;
border-image-width: initial;
border-image-width: revert;
border-image-width: revert-layer;
border-image-width: unset;

The border-image-width property may be specified using one, two, three, or four values chosen from the list of values below.

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

<length-percentage>

The width of the border, specified as a <length> or a <percentage>. Percentages are relative to the width of the border image area for horizontal offsets and the height of the border image area for vertical offsets. Must not be negative.

<number>

The width of the border, specified as a multiple of the corresponding border-width. Must not be negative.

auto

The width of the border is made equal to the intrinsic width or height (whichever is applicable) of the corresponding border-image-slice. If the image does not have the required intrinsic dimension, the corresponding border-width is used instead.

border-image-width = 
  [ <length-percentage [0,∞]> | <number [0,∞]> | auto ]{1,4}  

<length-percentage> = 
  <length>      |
  <percentage>  

This example creates a border image using the following ".png" file, which is 90 by 90 pixels:

Thus, each circle in the source image is 30 by 30 pixels.

HTML

<p>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy
   eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
   At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren,
   no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>

CSS

p {
  border: 20px solid;
  border-image: url("border.png") 30 round;
  border-image-width: 16px;
  padding: 40px;
}

Result

• Backgrounds and borders
• Learn CSS: Backgrounds and borders