/* <length> value */ mask-border-outset: 1rem; /* <number> value */ mask-border-outset: 1.5; /* vertical | horizontal */ mask-border-outset: 1 1.2; /* top | horizontal | bottom */ mask-border-outset: 30px 2 45px; /* top | right | bottom | left */ mask-border-outset: 7px 12px 14px 5px; /* Global values */ mask-border-outset: inherit; mask-border-outset: initial; mask-border-outset: unset;
- 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).
- The size of the mask border outset as a dimension.
- The size of the mask border outset as a multiple of the corresponding
|Applies to||all elements; In SVG, it applies to container elements excluding the |
|Computed value||as specified, but with relative lengths converted into absolute lengths|
This property doesn't appear to be supported anywhere yet. When it eventually starts to be supported, it will serve to move the mask away from the inner edge of the element's border box — you can use it to make the mask start from part way across the border, rather than the inside of it.
Chromium-based browsers support an outdated version of this property —
mask-box-image-outset — with a prefix:
mask-border page features a working example (using the out-of-date prefixed border mask properties supported in Chromium), so you can get an idea of the effect.
|CSS Masking Module Level 1
The definition of 'mask-border-outset' in that specification.
|Candidate Recommendation||Initial definition|