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

css

/* 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 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:
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:
Creates stacking contextyes

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

css

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

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

Specifications

Specification
CSS Masking Module Level 1
# the-mask

Browser compatibility

BCD tables only load in the browser

See also