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Summary

The mask property in CSS allows users to alter the visibility of an item by either partially or fully hiding the item. This is accomplished by either masking or clipping the image at specific points.

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:
Animatableas each of the properties of the shorthand:
  • mask-position: yes, as a repeatable list of , a simple list of , a length, percentage or calc(); when both values are lengths, they are interpolated as lengths; when both values are percentages, they are interpolated as percentages; otherwise, both values are converted into a calc() function that is the sum of a length and a percentage (each possibly zero), and these calc() functions have each half interpolated as real numbers.
  • mask-size: yes, as a repeatable list of , a simple list of , a length, percentage or calc(); when both values are lengths, they are interpolated as lengths; when both values are percentages, they are interpolated as percentages; otherwise, both values are converted into a calc() function that is the sum of a length and a percentage (each possibly zero), and these calc() functions have each half interpolated as real numbers.
Canonical orderthe unique non-ambiguous order defined by the formal grammar
Creates stacking contextyes

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: unset;

Values

If the value is a URI value, the element pointed to by the URI is used as an SVG mask.

<mask-layer>#

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

where
<mask-reference> = none | <image> | <mask-source>
<masking-mode> = alpha | luminance | match-source
<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

where
<image> = <url> | <image()> | <image-set()> | <element()> | <cross-fade()> | <gradient>
<mask-source> = <url>
<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( <rgb-component>#{3} )
<rgba()> = rgba( <rgb-component>#{3} , <alpha-value> )
<hsl()> = hsl( <hue>, <percentage>, <percentage> )
<hsla()> = hsla( <hue>, <percentage>, <percentage>, <alpha-value> )
<named-color> = <ident>
<deprecated-system-color> = ActiveBorder | ActiveCaption | AppWorkspace | Background | ButtonFace | ButtonHighlight | ButtonShadow | ButtonText | CaptionText | GrayText | Highlight | HighlightText | InactiveBorder | InactiveCaption | InactiveCaptionText | InfoBackground | InfoText | Menu | MenuText | Scrollbar | ThreeDDarkShadow | ThreeDFace | ThreeDHighlight | ThreeDLightShadow | ThreeDShadow | Window | WindowFrame | WindowText
<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
<rgb-component> = <integer> | <percentage>
<alpha-value> = <number>
<hue> = <number>
<color-stop> = <color> [ <percentage> | <length> ]?

Examples

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

.anothertarget { mask: url(resources.svg#c1); }

Specifications

Specification Status Comment
CSS Masking 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

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (for SVG) (Yes) (Yes) [*] ? (Yes) (Yes)
Applies to HTML Elements No support 3.5 (1.9.1) [*] No support No support No support
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support ? ? ? ? ?

[*] Starting in Gecko 10.0 (Firefox 10.0 / Thunderbird 10.0 / SeaMonkey 2.7), the default color space when handling masks is sRGB; previously, the default (and only supported color space) was linearRGB. This changes the appearance of mask effects, but brings Gecko into compliance with the second edition of the SVG 1.1 specification.

See also

Document Tags and Contributors

 Last updated by: Sebastianz,