The mask-origin CSS property sets the origin of a mask.

/* Keyword values */
mask-origin: content-box;
mask-origin: padding-box;
mask-origin: border-box;
mask-origin: margin-box;
mask-origin: fill-box;
mask-origin: stroke-box;
mask-origin: view-box;

/* Multiple values */
mask-origin: padding-box, content-box;
mask-origin: view-box, fill-box, border-box;

/* Non-standard keyword values */
-webkit-mask-origin: content;
-webkit-mask-origin: padding;
-webkit-mask-origin: border;

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

For elements rendered as a single box, this property specifies the mask positioning area. In other words, this property specifies the origin position of an image specified by the mask-image CSS property. For elements rendered as multiple boxes, such as inline boxes on several lines or boxes on several pages, it specifies which boxes box-decoration-break operates upon to determine the mask positioning area.


One or more of the keyword values listed below, separated by commas.



The position is relative to the content box.


The position is relative to the padding box. For single boxes 0 0 is the upper left corner of the padding edge, 100% 100% is the lower right corner.


The position is relative to the border box.


The position is relative to the margin box.

fill-box Experimental

The position is relative to the object bounding box.

stroke-box Experimental

The position is relative to the stroke bounding box.

view-box Experimental

Uses the nearest SVG viewport as reference box. If a viewBox attribute is specified for the element creating the SVG viewport, the reference box is positioned at the origin of the coordinate system established by the viewBox attribute and the dimension of the reference box is set to the width and height values of the viewBox attribute.

content Non-standard

Same as content-box.

padding Non-standard

Same as padding-box.

border Non-standard

Same as border-box.

Formal definition

Initial valueborder-box
Applies toall elements; In SVG, it applies to container elements excluding the <defs> element and all graphics elements
Computed valueas specified
Animation typediscrete

Formal syntax

mask-origin = 

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

<shape-box> =
<box> |

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


Setting mask origin to border-box

Try some of the other possible values by updating the CSS in the box below.


CSS Masking Module Level 1
# the-mask-origin

Browser compatibility

BCD tables only load in the browser

See also