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mask

The mask CSS shorthand property hides an element (partially or fully) by masking or clipping the image at specific points.

Note: As well as the properties listed below, the mask shorthand also resets mask-border to its initial value. It is therefore recommended to use the mask shorthand rather than other shorthands or the individual properties to override any mask settings earlier in the cascade. This will ensure that mask-border has also been reset to allow the new styles to take effect.

Constituent properties

This property is a shorthand for the following CSS properties:

Syntax

/* Keyword values */
mask: none;

/* Image values */
mask: url(mask.png); /* Pixel image used as mask */
mask: url(masks.svg#star); /* Element within SVG graphic used as mask */

/* Combined values */
mask: url(masks.svg#star) luminance; /* Element within SVG graphic used as luminance mask */
mask: url(masks.svg#star) 40px 20px; /* Element within SVG graphic used as mask positioned 40px from the top and 20px from the left */
mask: url(masks.svg#star) 0 0/50px 50px; /* Element within SVG graphic used as mask with a width and height of 50px */
mask: url(masks.svg#star) repeat-x; /* Element within SVG graphic used as horizontally repeated mask */
mask: url(masks.svg#star) stroke-box; /* Element within SVG graphic used as mask extending to the box enclosed by the stroke */
mask: url(masks.svg#star) exclude; /* Element within SVG graphic used as mask and combined with background using non-overlapping parts */

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

/* Multiple masks */
mask: url(masks.svg#star) left / 16px repeat-y, /* Element within SVG graphic is used as a mask on the left-hand side with a width of 16px */
    url(masks.svg#circle) right / 16px repeat-y; /* Element within SVG graphic is used as a mask on the right-hand side with a width of 16px */

Values

<mask-reference>

Sets the mask image source. See mask-image.

<masking-mode>

Sets the masking mode of the mask image. See mask-mode.

<position>

Sets the position of the mask image. See mask-position.

<bg-size>

Sets the size of the mask image. See mask-size.

<repeat-style>

Sets the repetition of the mask image. See mask-repeat.

<geometry-box>

If only one <geometry-box> value is given, it sets both mask-origin and mask-clip. If two <geometry-box> values are present, then the first sets mask-origin and the second sets mask-clip.

<geometry-box> | no-clip

Sets the area that is affected by the mask image. See mask-clip.

<compositing-operator>

Sets the compositing operation used on the current mask layer. See mask-composite.

Formal definition

Initial value as each of the properties of the shorthand:
Applies to all elements; In SVG, it applies to container elements excluding the <defs> element and all graphics elements
Inherited no
Percentages as each of the properties of the shorthand:
Computed value as each of the properties of the shorthand:
  • mask-image: as specified, but with url() values made absolute
  • mask-mode: as specified
  • mask-repeat: Consists of two keywords, one per dimension
  • mask-position: Consists of two keywords representing the origin and two offsets from that origin, each given as an absolute length (if given a <length>), otherwise as a percentage.
  • mask-clip: as specified
  • mask-origin: as specified
  • mask-size: as specified, but with relative lengths converted into absolute lengths
  • mask-composite: as specified
Animation type as each of the properties of the shorthand:
Creates stacking context yes

Formal syntax

mask = 
<mask-layer>#

<mask-layer> =
<mask-reference> ||
<position> [ / <bg-size> ]? ||
<repeat-style> ||
<geometry-box> ||
[ <geometry-box> | no-clip ] ||
<compositing-operator> ||
<masking-mode>

<mask-reference> =
none |
<image> |
<mask-source>

<position> =
[ left | center | right ] || [ top | center | bottom ] |
[ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ]? |
[ [ left | right ] <length-percentage> ] && [ [ top | bottom ] <length-percentage> ]

<bg-size> =
[ <length-percentage [0,∞]> | auto ]{1,2} |
cover |
contain

<repeat-style> =
repeat-x |
repeat-y |
[ repeat | space | round | no-repeat ]{1,2}

<geometry-box> =
<shape-box> |
fill-box |
stroke-box |
view-box

<compositing-operator> =
add |
subtract |
intersect |
exclude

<masking-mode> =
alpha |
luminance |
match-source

<image> =
<url> |
<gradient>

<mask-source> =
<url>

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

<shape-box> =
<box> |
margin-box

<url> =
url( <string> <url-modifier>* ) |
src( <string> <url-modifier>* )

<box> =
border-box |
padding-box |
content-box

Examples

Masking an image

.target {
  mask: url(#c1) luminance;
}

.anothertarget {
  mask: url(resources.svg#c1) 50px 30px/10px 10px repeat-x exclude;
}

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
mask
1While the property is recognized, values applied to it don't have any effect.
1The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
79While the property is recognized, values applied to it don't have any effect.
79The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
12–79
2From Firefox 10, the default color space when handling masks is sRGB. Previously, the default and only supported color space was linear RGB. This changes the appearance of mask effects, but brings Firefox into compliance with the second edition of the SVG 1.1 specification.
No
15While the property is recognized, values applied to it don't have any effect.
15The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
3.1While the property is recognized, values applied to it don't have any effect.
3.1The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
2While the property is recognized, values applied to it don't have any effect.
2The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
18While the property is recognized, values applied to it don't have any effect.
18The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
4From Firefox 10, the default color space when handling masks is sRGB. Previously, the default and only supported color space was linear RGB. This changes the appearance of mask effects, but brings Firefox into compliance with the second edition of the SVG 1.1 specification.
14While the property is recognized, values applied to it don't have any effect.
14The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
2While the property is recognized, values applied to it don't have any effect.
2The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.
1.0While the property is recognized, values applied to it don't have any effect.
1.0The prefixed property can be used with SVG and HTML with a slightly different syntax, which allows setting the non-standard -webkit-mask-attachment property.

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/CSS/mask