> ## Documentation Index
> Fetch the complete documentation index at: https://docs.comfy.org/llms.txt
> Use this file to discover all available pages before exploring further.

# MaskPreview - ComfyUI Built-in Node Documentation

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

> This documentation was AI-generated. If you find any errors or have suggestions for improvement, please feel free to contribute! [Edit on GitHub](https://github.com/Comfy-Org/embedded-docs/blob/main/comfyui_embedded_docs/docs/MaskPreview/en.md)

The MaskPreview node saves mask data as a preview image to your ComfyUI output directory, allowing you to visually inspect mask data during workflow execution. It converts the input mask into a format suitable for image display and saves it with a configurable filename prefix.

## Inputs

| Parameter         | Data Type      | Required | Range | Description                                                      |
| ----------------- | -------------- | -------- | ----- | ---------------------------------------------------------------- |
| `mask`            | MASK           | Yes      | -     | The mask data to be previewed and saved as an image              |
| `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 in the UI |

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