MaskPreview - ComfyUI Built-in Node Documentation

Complete documentation for the MaskPreview node in ComfyUI. Learn its inputs, outputs, parameters and usage.

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The MaskPreview node generates a visual preview of a mask by converting it into a 3-channel image format and saving it as a temporary file. It takes a mask input and reshapes it into a format suitable for image display, then saves the result to the temporary directory with a random filename prefix. This allows users to visually inspect mask data during workflow execution.

Inputs

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

Outputs

Output Name	Data Type	Description
ui	DICT	Contains the preview image information and metadata for display