MaskPreview - ComfyUI Built-in Node Documentation - ComfyUI

The MaskPreview node displays a visual preview of the mask data directly in the ComfyUI interface, without saving it to the output directory. This lets you inspect the exact mask values at any point in your workflow.

Inputs

Parameter	Description	Data Type	Required	Range
`mask`	The mask data to preview	MASK	Yes	-
`filename_prefix`	Prefix for the preview filename (default: “ComfyUI”)	STRING	No	-
`prompt`	Prompt information for metadata (automatically provided)	PROMPT	No	-
`extra_pnginfo`	Additional PNG information for metadata (automatically provided)	EXTRA_PNGINFO	No	-

The prompt and extra_pnginfo inputs are hidden and are supplied automatically by the ComfyUI system; you do not need to connect them manually.

Outputs

Output Name	Description	Data Type
`mask`	The mask data that was previewed, returned unchanged for further use in the workflow	MASK

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