# Source: https://docs.comfy.org/api-reference/cloud/file/upload-a-mask-image.md

> ## 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.

# Upload a mask image

> Upload a mask image to be applied to an existing image



## OpenAPI

````yaml openapi-cloud.yaml post /api/upload/mask
openapi: 3.0.3
info:
  title: Comfy Cloud API
  description: >
    <Warning>

    **Experimental API:** This API is experimental and subject to change. 

    Endpoints, request/response formats, and behavior may be modified without
    notice.

    </Warning>


    API for Comfy Cloud - Run ComfyUI workflows on cloud infrastructure.


    This API allows you to interact with Comfy Cloud programmatically,
    including:

    - Submitting and managing workflows

    - Uploading and downloading files

    - Monitoring job status and progress


    ## Cloud vs OSS ComfyUI Compatibility


    Comfy Cloud implements the same API interfaces as OSS ComfyUI for maximum
    compatibility,

    but some fields are accepted for compatibility while being handled
    differently or ignored:


    | Field | Endpoints | Cloud Behavior |

    |-------|-----------|----------------|

    | `subfolder` | `/api/view`, `/api/upload/*` | **Ignored** - Cloud uses
    content-addressed storage (hash-based). Returned in responses for
    client-side organization. |

    | `type` (input/output/temp) | `/api/view`, `/api/upload/*` | Partially used
    - All files stored with tag-based organization rather than directory
    structure. |

    | `overwrite` | `/api/upload/*` | **Ignored** - Content-addressed storage
    means identical content always has the same hash. |

    | `number`, `front` | `/api/prompt` | **Ignored** - Cloud uses its own fair
    queue scheduling per user. |

    | `split`, `full_info` | `/api/userdata` | **Ignored** - Cloud always
    returns full file metadata. |


    These fields are retained in the API schema for drop-in compatibility with
    existing ComfyUI clients and workflows.
  version: 1.0.0
  license:
    name: GNU General Public License v3.0
    url: https://github.com/comfyanonymous/ComfyUI/blob/master/LICENSE
servers:
  - url: https://cloud.comfy.org
    description: Comfy Cloud API
security:
  - ApiKeyAuth: []
tags:
  - name: workflow
    description: |
      Submit workflows for execution and manage the execution queue.
      This is the primary way to run ComfyUI workflows on the cloud.
  - name: job
    description: |
      Monitor job status, view execution history, and manage running jobs.
      Jobs are created when you submit a workflow via POST /api/prompt.
  - name: asset
    description: |
      Upload, download, and manage persistent assets (images, models, outputs).
      Assets provide durable storage with tagging and metadata support.
  - name: file
    description: |
      Legacy file upload and download endpoints compatible with local ComfyUI.
      For new integrations, consider using the Assets API instead.
  - name: model
    description: |
      Browse available AI models. Models are pre-loaded on cloud infrastructure.
  - name: node
    description: |
      Get information about available ComfyUI nodes and their inputs/outputs.
      Useful for building dynamic workflow interfaces.
  - name: user
    description: |
      User account information and personal data storage.
  - name: system
    description: |
      Server status, health checks, and system information.
paths:
  /api/upload/mask:
    post:
      tags:
        - file
      summary: Upload a mask image
      description: Upload a mask image to be applied to an existing image
      operationId: uploadMask
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              type: object
              required:
                - image
                - original_ref
              properties:
                image:
                  type: string
                  format: binary
                  description: The mask image file to upload
                original_ref:
                  type: string
                  description: JSON string containing reference to the original image
      responses:
        '200':
          description: Mask uploaded successfully
          content:
            application/json:
              schema:
                type: object
                properties:
                  name:
                    type: string
                    description: Filename of the uploaded mask
                  subfolder:
                    type: string
                    description: Subfolder path where mask was saved
                  type:
                    type: string
                    description: Type of upload (e.g., "output")
                  metadata:
                    type: object
                    description: Additional metadata for mask detection and re-editing
                    properties:
                      is_mask:
                        type: boolean
                        description: Whether this file is a mask
                      original_hash:
                        type: string
                        description: Hash of the original unmasked image
                      mask_type:
                        type: string
                        description: Type of mask (e.g., "painted_masked")
                      related_files:
                        type: object
                        description: Related mask layer files (if available)
                        properties:
                          mask:
                            type: string
                            description: Hash of the mask layer
                          paint:
                            type: string
                            description: Hash of the paint layer
                          painted:
                            type: string
                            description: Hash of the painted image
        '400':
          description: Bad request
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '500':
          description: Internal server error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
components:
  schemas:
    ErrorResponse:
      type: object
      required:
        - code
        - message
      properties:
        code:
          type: string
        message:
          type: string
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: X-API-Key
      description: |
        API key authentication. Generate an API key from your account settings
        at https://comfy.org/account. Pass the key in the X-API-Key header.

````