Layer masks are the single most important skill in Photoshop after layers themselves. Once they click, editing becomes non-destructive, flexible and far less stressful, because you can always change your mind. Here is how they work.
The one rule to remember
A layer mask is grayscale, and it follows one simple rule:
- White reveals the layer.
- Black hides the layer.
- Gray makes it partly transparent.
That is the whole concept. Everything else is just applying it.
How to add a layer mask
- Select the layer you want to mask in the Layers panel.
- Click the Add Layer Mask button at the bottom of the panel (a rectangle with a circle inside).
- A white mask thumbnail appears beside the layer. White means the whole layer is currently visible.
How to paint on a mask
- Click the mask thumbnail to select it (not the layer image).
- Choose the Brush tool and set your foreground colour to black.
- Paint over the areas you want to hide. They disappear, but the pixels are still there.
- Switch the brush to white to paint those areas back.
Press X to swap between black and white as you work. This paint-to-hide, paint-to-reveal flow is the heart of masking.
Refining your mask
Use a soft brush for gentle, blended transitions and a hard brush for crisp edges. Lower the brush opacity to build up partial transparency gradually. For cutting out a subject, combine masks with a selection: make your selection first, then add a mask, and Photoshop fills the mask for you.
Masks power almost everything advanced in Photoshop, from removing backgrounds to blending photos and adjustment layers.
Keep going
Masks are where casual users become confident editors. The full Adobe Photoshop course covers masking, selections and compositing in depth, with real projects, and you can start with the free lessons first.