Whenever I create a transparency mask with multiple objects one of them gets automatically moved to the transparency zone. I have no idea why is this happening, it never used to do such thing. I tried ugrouping all objects, but the result is the same. Tried ticking all transparency options and nohing.

Here is a gif to illustrate the problem.

EDIT: Now it's happening when I'm grouping any object. One of them dissapears. What da hell?

enter image description here

  • I suspect the top object is not grouped with the other ones.
    – LeoNas
    Commented Oct 31, 2019 at 20:10
  • Try grouping the objects you wish to use as a mask.
    – Billy Kerr
    Commented Oct 31, 2019 at 20:41
  • I did, and the result was the same too.
    – Cristóbal
    Commented Oct 31, 2019 at 20:56

1 Answer 1


This isn't a "bug".... This is how Illustrator functions and has always functioned where Opacity Masks are concerned. A "bug" is an instance of repeatable behavior which is unexpected. What you have outlined is entirely expected behavior.

Opacity Masks assume the top object of a selection should define the mask. It doesn't see "groups" So the top single object or compound shape will define the mask.

Therefore yes, the top most object will become the mask shape. There are a few ways to circumvent that, I've outlined one such method below, but there are others.

If you want that entire shape to be the mask.... make it one shape via Pathfinder or create a compound shape. As 3 separate objects, the top object will always define the mask.... and Groups don't count.

To create a mask containing all 3 of your objects...

  • Copy the Objects

  • Draw some random shape on top of everything

  • Select All

  • Click the Make Mask button.

  • Delete the random shape from the mask

  • Paste the previously copied objects on the mask (in front or in back to retain position)

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