Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The -webkit-mask-position-x CSS property sets the initial horizontal position of a mask image.


/* Keyword values */
-webkit-mask-position-x: left;
-webkit-mask-position-x: center;
-webkit-mask-position-x: right;

/* <percentage> values */
-webkit-mask-position-x: 100%;
-webkit-mask-position-x: -50%;

/* <length> values */
-webkit-mask-position-x: 50px;
-webkit-mask-position-x: -1cm;

/* Multiple values */

/* Global values */
-webkit-mask-position-x: inherit;
-webkit-mask-position-x: initial;
-webkit-mask-position-x: revert;
-webkit-mask-position-x: revert-layer;
-webkit-mask-position-x: unset;



A length indicating the position of the left edge of the image relative to the box's left padding edge. Percentages are calculated against the horizontal dimension of the box padding area. That means, a value of 0% means the left edge of the image is aligned with the box's left padding edge and a value of 100% means the right edge of the image is aligned with the box's right padding edge.


Equivalent to 0%.


Equivalent to 50%.

Equivalent to 100%.

Formal definition

Initial value0%
Applies toall elements
Percentagesrefer to the size of the box itself
Computed valuefor <length> the absolute value, otherwise a percentage
Animation typediscrete

Formal syntax

-webkit-mask-position-x =
  [ <length-percentage> | left | center | right ]#


Horizontally positioning a mask image

.exampleOne {
  -webkit-mask-image: url(mask.png);
  -webkit-mask-position-x: right;

.exampleTwo {
  -webkit-mask-image: url(mask.png);
  -webkit-mask-position-x: 25%;


Not part of any standard.

Browser compatibility

BCD tables only load in the browser

See also