Layer Masks Explained: Non-Destructive Editing for Beginners

Here's layer masks explained in one sentence: a mask is a grayscale stencil attached to a layer, where black hides that layer, white shows it, and gray is somewhere in between. That's the entire mechanism. The reason every working editor leans on it is what it replaces: the eraser. Erased pixels are gone, and in twenty minutes, when you change your mind about an edge, you start over. Paint the same area black on a mask instead and the pixels are still there, hidden. Change your mind, paint white, and they come back. This post walks through the whole idea in ImageCraft, ClipCraft's free browser editor, using a demo you can rebuild in about two minutes.

Never erase. Hide.

The eraser feels natural because it behaves like the physical object. That's also why it's a trap. Every stroke is a commitment, and a stack of committed strokes is a stack of decisions you can no longer revisit. Undo helps until the history runs out (ImageCraft keeps 14 whole-stack snapshots), and it can't take back stroke three while keeping strokes four through nine.

A mask turns the same gesture into metadata. The layer keeps every pixel it ever had; the mask just decides which of them render. You can soften the boundary later, bring the whole thing back at half strength, flip it inside out, or throw the mask away and start fresh, all without touching the image underneath. Once this clicks, the eraser starts to look like a tool for cleaning up scratch layers and nothing else. That's roughly the line between beginner edits and everything after.

Layer masks explained with a two-layer demo

The clearest way to see a mask work is two versions of the same scene stacked on top of each other. I made a day scene and a night scene of the same hills, loaded the day version into ImageCraft, then dropped the night version on top. Drops after the first one land as new layers, so the Layers panel now shows both, with the night layer completely covering the day one.

Now the mask. With the night layer active, click the ▣ button at the bottom of the Layers panel (or the Add layer mask button in the Properties panel). A white thumbnail appears next to the layer thumbnail. White means "show everything," so nothing changes yet. The mask thumbnail is selected the moment it's created, with a green ring around it; that ring matters, because it tells you your paint strokes will land on the mask, not on the image.

Grab the Brush, press D to reset the color chips to black and white, and paint across the sky. Wherever the black lands, the night layer disappears and the day layer shows through. I painted a rough blob over the moon and got the sun back.

The half of this workflow nobody tells beginners: press X while painting. It swaps the foreground and background chips, so you bounce between black (hide) and white (reveal) without leaving the canvas. Overshot an edge? X, paint it back, X, keep going. Masking is really just painting with those two keys under your left hand. If you ever lose track of where the mask is dark, Ctrl+click the mask thumbnail and ImageCraft loads its white areas as a selection.

Density and Feather: dials you can turn forever

Click any mask thumbnail and the Properties panel switches to the mask view. Two sliders live at the top. Density (default 100%) scales how strongly the mask hides; drop it to 40% and everything you painted black becomes 60% visible, a quick way to turn a hard hide into a subtle blend. Feather (0 to 50 px) blurs the mask boundary without touching the mask pixels, so a crunchy brush edge melts into a soft transition and can come back to crisp at any time.

Below the sliders: Invert flips the whole mask (handy right after creating one, as you'll see in a minute), Disable turns it off without losing it, Apply bakes it into the pixels permanently (this one is destructive, and it only works on pixel layers), and the Refine row nudges the edge. Smooth softens jagged boundaries, while Expand and Contract grow or shrink the revealed area by about 1.5 px per click. Free Transform works on a selected mask too, so you can scale or warp the stencil itself.

Selections become masks, which is the cutout workflow

Painting is one way to build a mask. The faster way, most days, is a selection. If marching ants are active when you press the ▣ button, the mask is built from the selection: selected areas stay visible, everything else goes transparent. Select a subject with any of the selection tools (marquee, wand, or a click of AI Select) and one button turns it into a cutout with the background hidden rather than deleted, so every refinement tool above still applies. That whole pipeline has its own post if cutouts are what brought you here, and the wider tour of the editor lives in the ImageCraft overview.

You need a free account to use the editor, but everything in this post runs client-side and costs nothing: masks, adjustment layers, the brush engine, PNG export. Your image never leaves your machine.

Masked adjustments: the single most useful trick in retouching

Here's where masks stop being a cutout feature and become how you edit. Adjustment layers in ImageCraft (17 types: Levels, Curves, Hue/Saturation, Black & White, and so on) change every layer below them, and each one is created with its own mask automatically. Which means any adjustment can be painted onto part of the image.

The recipe is three steps. Add the adjustment layer. Click its mask thumbnail and hit Invert, so the mask is black and the effect applies nowhere. Then paint white exactly where you want it. Brighten just a face with a Curves layer, or desaturate everything except the product. Photographers call this dodging and burning with training wheels, except the training wheels are re-editable forever.

I ran it on the demo scene: a Black & White adjustment, mask inverted, then white paint over the sun. The sun went gray while the rest of the image kept its color, and both the amount and the area stay adjustable afterward. Small honest note from doing exactly this: while an adjustment layer is active, the options bar shows an amber "Select a pixel layer to paint" hint. It's wrong in this one case. As long as the mask thumbnail carries the green ring, your strokes land on the mask just fine.

A selection works here too. Select the sky first, then create a Levels layer, and its mask starts from the selection, already local. Between that and the paint-it-in recipe, you can stop thinking of adjustments as global operations at all.

Clipping masks, in one paragraph

A clipping mask is the same hide-don't-delete idea driven by a different stencil: the layer underneath. Toggle "Clip to layer below" on an adjustment and it applies only where that lower layer has pixels; the row shows a small ↳ clip tag. It's the clean way to color-grade one cutout without the grade spilling onto the rest of the composite, and it stacks with a regular painted mask on the same layer.

Where to go from here

• Rebuild the demo: any two images, mask the top one, paint black with a big soft brush. Two minutes, and the concept sticks better than any diagram.
• Next photo you edit, forbid yourself the eraser. Every hide goes through a mask, every local tweak through a masked adjustment.
• If an object needs to leave the frame entirely instead of hiding, that's a different tool: see removing objects from photos.

Masks, adjustment layers, and the layered project saves that preserve them are all part of the free editor; paid plans mainly add storage for saved projects and tokens for the optional cloud AI features. Nothing in this post used either.