Mask Editor - Create and Edit Masks in ComfyUI

Learn how to use the Mask Editor in ComfyUI, including tools, layers, settings, and shortcuts

The Mask Editor is a built-in tool in ComfyUI that lets you create and edit masks directly on your images — no external image editor needed. It supports multiple drawing tools, layer management, undo/redo, canvas transformations, and GPU-accelerated brush rendering.

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How to Open

There are three ways to open the Mask Editor:

1. Selection Toolbox — Select a Load Image node, then click the Mask icon button in the selection toolbar above the node.
2. Image Overlay — Hover over the image preview (gallery mode), then click the Edit or mask image button (mask icon) that appears in the top-left corner.
3. Right-Click Menu — Right-click a Load Image node and select Open in Mask Editor from the context menu.

The Mask Editor is available in both Graph Mode and App Mode.

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Interface Overview

The Mask Editor opens as a modal dialog with four main areas:

#	Area	Location	Description
1	Top Bar	Top	Header with undo/redo, canvas transforms, invert/clear, save/cancel
2	Tool Panel	Left	Tool selection and zoom info
—	Pointer Zone	Center	The main canvas area for drawing and editing
3	Side Panel	Right	Tool-specific settings and layer controls

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Tools

The tool panel on the left side offers five tools. Select a tool to activate it, and the right panel will show its settings.

#	Tool	Layer	Description
1	Mask Pen	Mask	Primary tool for drawing mask regions. Left-click and drag to paint mask on the image.
2	Paint Pen	RGB (Paint)	Paint directly onto the image’s RGB layer. Useful for inpainting or touching up the base image.
3	Eraser	Mask / RGB	Erase parts of an existing mask or paint layer.
4	Paint Bucket	Mask	Flood-fill tool based on color similarity. Click a pixel to fill the connected region with a mask; click an already-masked area to erase from the mask. Tolerance controls how broadly the fill spreads.
5	Color Select	Mask	Selectively mask all pixels matching a target color, with advanced matching algorithms (Simple HSL / LAB).

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TopBar Actions

The top bar provides canvas-wide operations:

#	Action	Description
1	Undo (Ctrl+Z)	Revert the last action
2	Redo (Ctrl+Shift+Z / Ctrl+Y)	Reapply a reverted action
3	Rotate Left	Rotate all layers 90° counter-clockwise
4	Rotate Right	Rotate all layers 90° clockwise
5	Mirror Horizontal	Flip all layers horizontally
6	Mirror Vertical	Flip all layers vertically
7	Invert	Invert the mask (black ↔ white)
8	Clear	Clear the entire mask
9	Save	Save the mask and close the editor
10	Cancel	Close without saving

Note: Rotate and mirror operations affect all three layers (mask, paint, and base image) simultaneously. GPU-accelerated textures are recreated after transforms.

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Layers

The right panel includes a Layers section where you can toggle visibility of each layer independently:

• Mask Layer: The mask overlay. You can adjust its opacity and blending mode:
  • Black — Mask renders as black overlay
  • White — Mask renders as white overlay
  • Negative — Inverted mask rendering
• Paint Layer: The RGB paint layer (visible when using Paint Pen)
• Base Image Layer: The original source image

Click Activate Layer on a layer to switch drawing focus to it.

Refer to the main editor screenshot above — the right panel includes brush settings and the Layers section at the bottom.

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Brush Settings

When a brush-based tool (Mask Pen, Paint Pen, or Eraser) is active, the side panel shows brush settings:

Setting	Range	Description
Shape	Arc / Rect	Round brush or square brush
Color	Any hex color	The paint color (for Paint Pen) or mask color
Thickness	1–250	Brush diameter in pixels
Opacity	0–1	Brush stroke transparency
Hardness	0–1	Edge softness. 1 = hard edge, 0 = very soft
Step Size	1–100	Spacing between brush dabs. Lower values give smoother strokes

Use Reset to Default to restore the default brush parameters.

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Canvas Navigation & Shortcuts

Shortcut	Action
Space + Drag	Pan the canvas
Ctrl + Scroll	Zoom in/out
Click zoom %	Reset zoom to 100%
Ctrl + Z	Undo
Ctrl + Shift + Z or Ctrl + Y	Redo
Alt + Right-click + Drag	Adjust brush: left/right changes size, up/down changes hardness

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Settings

In the ComfyUI Settings panel, you can configure the following Mask Editor options:

Setting	Category	Default	Description
Brush adjustment speed multiplier	Mask Editor → Brush Adjustment → Sensitivity	1.0 (0.1–2.0)	How quickly the brush size and hardness change when using Alt+Right-click drag
Lock brush adjustment to dominant axis	Mask Editor → Brush Adjustment → Use Dominant Axis	On	When enabled, the adjustment affects only size OR hardness based on your dominant movement direction

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Video Tutorial

Note: This video demonstrates an older version of the Mask Editor (Nodes 1.0 UI) showing brush size adjustment and mask preview creation. The overall workflow remains the same in the current version.