mask-border

The mask-border CSS shorthand property lets you create a mask along the edge of an element's border.

Constituent properties

This property is a shorthand for the following CSS properties:

• mask-border-mode
• mask-border-outset
• mask-border-repeat
• mask-border-slice
• mask-border-source
• mask-border-width

Syntax

/* source | slice */
mask-border: url('border-mask.png') 25;

/* source | slice | repeat */
mask-border: url('border-mask.png') 25 space;

/* source | slice | width */
mask-border: url('border-mask.png') 25 / 35px;

/* source | slice | width | outset | repeat | mode */
mask-border: url('border-mask.png') 25 / 35px / 12px space alpha;

/* Global values */
mask-border: inherit;
mask-border: initial;
mask-border: revert;
mask-border: unset;

Values

<'mask-border-source'>

The source image. See mask-border-source.

<'mask-border-slice'>

The dimensions for slicing the source image into regions. Up to four values may be specified. See mask-border-slice.

<'mask-border-width'>

The width of the border mask. Up to four values may be specified. See mask-border-width.

<'mask-border-outset'>

The distance of the border mask from the element's outside edge. Up to four values may be specified. See mask-border-outset.

<'mask-border-repeat'>

Defines how the edge regions of the source image are adjusted to fit the dimensions of the border mask. Up to two values may be specified. See mask-border-repeat.

<'mask-border-mode'>

Defines whether the source image is treated as a luminance mask or alpha mask. See mask-border-mode.

Formal definition

Formal syntax

<'mask-border-source'> || <'mask-border-slice'> [ / <'mask-border-width'>? [ / <'mask-border-outset'> ]? ]? || <'mask-border-repeat'> || <'mask-border-mode'>

Examples

Setting a bitmap-based mask border

In this example, we will mask an element's border with a diamond pattern. The source for the mask is a ".png" file of 90 by 90 pixels, with three diamonds going vertically and horizontally:

To match the size of a single diamond, we will use a value of 90 divided by 3, or 30, for slicing the image into corner and edge regions. A repeat value of round will make the mask slices fit evenly, i.e., without clipping or gaps.

Specifications

Browser compatibility

See also

• mask-border-mode
• mask-border-outset
• mask-border-repeat
• mask-border-source
• mask-border-width