border-image-slice

The border-image-slice CSS property divides the image specified by border-image-source in nine regions: the four corners, the four edges and the middle.

/* border-image-slice: slice */
border-image-slice: 30%; 
/* border-image-slice: vertical horizontal */
border-image-slice: 10% 30%;
/* border-image-slice: top horizontal bottom */
border-image-slice: 30 30% 45;
/* border-image-slice: top right bottom left */
border-image-slice: 7 12 14 5; 
/* border-image-slice: … fill */
/* The fill value can be placed between any value */
border-image-slice: 10% fill 7 12;
/* Global values */
border-image-slice: inherit;
border-image-slice: initial;
border-image-slice: unset;

It does this by specifying 4 inwards offsets.

Four values control the position of the slice lines. If some are not specified, they are inferred from the other with the usual 4-value syntax of CSS.

The middle is not used by the border itself but is used as a background-image if the keyword fill is set. The keyword can be set at any position in the property (before, after or between the other values).

The border-image-repeat, border-image-width, border-image-outset properties define how these images will be used.

The shorthand CSS property border-image may reset this property to its default value.

Syntax

This property may take one, two, three, or four values.

With one value:

• the value is a slice.

With two values:

• the values specify vertical and horizontal positions.

With three values:

• the values specify top, horizontal, and bottom positions.

With four values:

• the values specify top, right, bottom, left positions.

The fill value can be placed between any values.

Values

slice

Is a <number> or a <percentage> of the offset for the four slicing lines. The <number> represents pixels for raster images and coordinates for vector images. Also, <percentage> values are relative to the height or width of the image, whichever is adequate. Negative values are invalid and values greater than the relevant size, height or width, are clamped to 100%.

horizontal

Is a <number> or a <percentage> of the offset for the two slicing lines corresponding to the horizontal edges, the right and the left ones. The <number> represents pixels for raster images and coordinates for vector images. Also, <percentage> values are relative to the height or width of the image, whichever is adequate. Negative values are invalid and values greater than the relevant size, height or width, are clamped to 100%.

vertical

Is a <number> or a <percentage> of the offset for the two slicing lines corresponding to the vertical edges, the top and the bottom ones. The <number> represents pixels for raster images and coordinates for vector images. Also, <percentage> values are relative to the height or width of the image, whichever is adequate. Negative values are invalid and values greater than the relevant size, height or width, are clamped to 100%.

top

Is a <number> or a <percentage> of the offset for the top slicing line. The <number> represents pixels for raster images and coordinates for vector images. Also, <percentage> values are relative to the height or width of the image, whichever is adequate. Negative values are invalid and values greater than the relevant size, height or width, are clamped to 100%.

bottom

Is a <number> or a <percentage> of the offset for the bottom slicing line. The <number> represents pixels for raster images and coordinates for vector images. Also, <percentage> values are relative to the height or width of the image, whichever is adequate. Negative values are invalid and values greater than the relevant size, height or width, are clamped to 100%.

right

Is a <number> or a <percentage> of the offset for the right slicing line. The <number> represents pixels for raster images and coordinates for vector images. Also, <percentage> values are relative to the height or width of the image, whichever is adequate. Negative values are invalid and values greater than the relevant size, height or width, are clamped to 100%.

left

Is a <number> or a <percentage> of the offset for the left slicing line. The <number> represents pixels for raster images and coordinates for vector images. Also, <percentage> values are relative to the height or width of the image, whichever is adequate. Negative values are invalid and values greater than the relevant size, height or width, are clamped to 100%.

fill

Is a keyword whose presence forces the use of the middle image slice to be displayed over the background image, its size and height are resized like those of the top and left image slices, respectively.

inherit

Is a keyword indicating that all four values are inherited from their parent's element calculated value.

Formal syntax

<number-percentage>{1,4} && fill?
where 
<number-percentage> = <number> | <percentage>

Specifications

Browser compatibility

[1] Until Gecko 47.0 (Firefox 47.0 / Thunderbird 47.0 / SeaMonkey 2.44) SVGs without viewport were not sliced correctly (bug 619500). Starting from Gecko 48.0 (Firefox 48.0 / Thunderbird 48.0 / SeaMonkey 2.45) they are displayed the same like SVGs with viewport, though if the slices are not exactly 50%, they are incorrectly stretched (bug 1264809). This was fixed in Gecko 49.0 (Firefox 49.0 / Thunderbird 49.0 / SeaMonkey 2.46), though there's still an issue for SVGs without viewport when e10s is disabled (bug 1290782).

Also, small SVGs are incorrectly stretched, because percentages in border-image-slice are computed to integers instead of floats (bug 1284797).

See also

• Illustrated description of the 1-to-4-value syntax