The mask CSS property alters the visibility of an element by either partially or fully hiding it. This is accomplished by either masking or clipping the image at specific points.

/* 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: unset;

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.

Initial valueas each of the properties of the shorthand:
Applies toall elements; In SVG, it applies to container elements excluding the <defs> element and all graphics elements
Inheritedno
Percentagesas each of the properties of the shorthand:
Mediavisual
Computed valueas 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 typeas each of the properties of the shorthand:
Canonical orderper grammar
Creates stacking contextyes

Syntax

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 syntax

<mask-layer>#

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

where
<mask-reference> = none | <image> | <mask-source>
<position> = [[ left | center | right | top | bottom | <length-percentage> ] | [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ] | [ center | [ left | right ] <length-percentage>? ] && [ center | [ top | bottom ] <length-percentage>? ]]
<bg-size> = [ <length-percentage> | 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

where
<image> = <url> | <image()> | <image-set()> | <element()> | <cross-fade()> | <gradient>
<mask-source> = <url>
<length-percentage> = <length> | <percentage>
<shape-box> = <box> | margin-box

where
<image()> = image( [ [ <image> | <string> ]? , <color>? ]! )
<image-set()> = image-set( <image-set-option># )
<element()> = element( <id-selector> )
<cross-fade()> = cross-fade( <cf-mixing-image> , <cf-final-image>? )
<gradient> = <linear-gradient()> | <repeating-linear-gradient()> | <radial-gradient()> | <repeating-radial-gradient()>
<box> = border-box | padding-box | content-box

where
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>
<image-set-option> = [ <image> | <string> ] <resolution>
<cf-mixing-image> = <percentage>? && <image>
<cf-final-image> = <image> | <color>
<linear-gradient()> = linear-gradient( [ <angle> | to <side-or-corner> ]? , <color-stop-list> )
<repeating-linear-gradient()> = repeating-linear-gradient( [ <angle> | to <side-or-corner> ]? , <color-stop-list> )
<radial-gradient()> = radial-gradient( [ <ending-shape> || <size> ]? [ at <position> ]? , <color-stop-list> )
<repeating-radial-gradient()> = repeating-radial-gradient( [ <ending-shape> || <size> ]? [ at <position> ]? , <color-stop-list> )

where
<rgb()> = rgb( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<rgba()> = rgba( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<hsl()> = hsl( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
<hsla()> = hsla( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
<side-or-corner> = [ left | right ] || [ top | bottom ]
<color-stop-list> = <color-stop>#{2,}
<ending-shape> = circle | ellipse
<size> = closest-side | farthest-side | closest-corner | farthest-corner | <length> | <length-percentage>{2}

where
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>
<color-stop> = <color> <length-percentage>?

Examples

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

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

Specifications

Specification Status Comment
CSS Masking Module Level 1
The definition of 'mask' in that specification.
Candidate Recommendation Extends its usage to HTML elements.
Extends its syntax by making it a shorthand for the new mask-* properties defined in that specification.
Scalable Vector Graphics (SVG) 1.1 (Second Edition)
The definition of 'mask' in that specification.
Recommendation Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support

11

Yes -webkit- 2

Yes Yes3 No

Yes1

Yes -webkit- 2

41

Yes -webkit- 2

Applies to HTML elements Yes -webkit- ?3.5 No Yes -webkit- No
Shorthand for mask-* properties Yes -webkit- ?53 No Yes -webkit- No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support

2.1

Yes -webkit-

? Yes Yes ? ?3.2 -webkit-
Applies to HTML elements ? ? ? ? ? ? ?
Shorthand for mask-* properties ? ? ?53 ? ? ?

1. While the property is recognized, values applied to it don't have any effect.

2. The 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. From 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.

See also

Document Tags and Contributors

 Last updated by: fscholz,