CSS · Properties — CSS Masking
mask-origin
The CSS mask-origin property. Initial value: border-box. Not inherited.
Syntax
mask-origin: <coord-box>#Example
Try it
Notes
Media: visual. Applies to: allElementsSVGContainerElements. Computed value: asSpecified.
More in this group
Learn this in the course
Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.