CSS -webkit-mask-size Property Reference

The CSS -webkit-mask-size property is a nonstandard property in WebKit Extensions. Review its formal syntax, computed behavior, and practical declarations.

Updated 2026-08-12

-webkit-mask-size overview

The CSS -webkit-mask-size property is a nonstandard property in WebKit Extensions. Review its formal syntax, computed behavior, and practical declarations.

The property is not inherited by default. Use an explicit global keyword when inheritance is intended.

Syntax and formal definition

-webkit-mask-size formal syntax

Field	Value
Formal syntax	<bg-size>#
Initial value	auto auto
Applies to	allElements
Inherited	No
Percentages	relativeToBackgroundPositioningArea
Computed value	asSpecified
Animation type	discrete
Media	visual
Specification group	WebKit Extensions
Status	Nonstandard

Practical examples

These declarations demonstrate valid ways to set -webkit-mask-size. The initial and inherit global keywords remain available even when a property-specific value is preferable.

-webkit-mask-size live example

CSS

.reset-example {
  -webkit-mask-size: initial;
}

.inherit-example {
  -webkit-mask-size: inherit;
}

@supports (-webkit-mask-size: initial) {
  .supported {
    -webkit-mask-size: initial;
  }
}