maskUnits

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

The maskUnits attribute indicates which coordinate system to use for the geometry properties of the <mask> element.

You can use this attribute with the following SVG elements:

<mask>

Example

html,
body,
svg {
  height: 100%;
}

html

<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
  <mask
    id="myMask1"
    maskUnits="userSpaceOnUse"
    x="20%"
    y="20%"
    width="60%"
    height="60%">
    <rect fill="black" x="0" y="0" width="100%" height="100%" />
    <circle fill="white" cx="50" cy="50" r="35" />
  </mask>

  <mask
    id="myMask2"
    maskUnits="objectBoundingBox"
    x="20%"
    y="20%"
    width="60%"
    height="60%">
    <rect fill="black" x="0" y="0" width="100%" height="100%" />
    <circle fill="white" cx="50" cy="50" r="35" />
  </mask>

  <!-- Some reference rect to materialized the mask -->
  <rect id="r1" x="0" y="0" width="45" height="45" />
  <rect id="r2" x="0" y="55" width="45" height="45" />
  <rect id="r3" x="55" y="55" width="45" height="45" />
  <rect id="r4" x="55" y="0" width="45" height="45" />

  <!-- The first 3 rect are masked with useSpaceOnUse units -->
  <use mask="url(#myMask1)" href="#r1" fill="red" />
  <use mask="url(#myMask1)" href="#r2" fill="red" />
  <use mask="url(#myMask1)" href="#r3" fill="red" />

  <!-- The last rect is masked with objectBoundingBox units -->
  <use mask="url(#myMask2)" href="#r4" fill="red" />
</svg>

mask

For <mask>, maskUnits defines the coordinate system in use for the geometry attributes (x, y, width and height) of the element.

Value	`userSpaceOnUse` \| `objectBoundingBox`
Default value	`objectBoundingBox`
Animatable	Yes

userSpaceOnUse: This value indicates that all coordinates for the geometry attributes refer to the user coordinate system as defined when the mask was created.
objectBoundingBox: This value indicates that all coordinates for the geometry attributes represent fractions or percentages of the bounding box of the element to which the mask is applied. A bounding box could be considered the same as if the content of the <mask> were bound to a "0 0 1 1" viewBox.

Specifications

Specification
CSS Masking Module Level 1 # element-attrdef-mask-maskunits

Browser compatibility

BCD tables only load in the browser