Flux Generation API

openapi: 3.1.0
info:
  title: Flux Image Editing Generation API
  description: REST API for editing and transforming existing images using Black Forest Labs' FLUX.1 Kontext models. The Kontext models accept an input image and a text prompt describing desired edits, returning a modified image. They support context-aware in-painting, object replacement, style transfer, background changes, and image-to-image transformations while preserving important visual context. Authentication requires an API key in the X-Key header. Requests are asynchronous and require polling for results.
  version: v1
  contact:
    name: Black Forest Labs Support
    url: https://docs.bfl.ai/
  termsOfService: https://bfl.ai/legal/flux-api-service-terms
servers:
- url: https://api.bfl.ai/v1
  description: Black Forest Labs Flux API
security:
- apiKeyAuth: []
tags:
- name: Generation
  description: Endpoints for submitting image generation requests using FLUX models. Each endpoint targets a specific model variant and returns a task ID for polling.
paths:
  /flux-pro-1.1:
    post:
      operationId: generateFluxPro11
      summary: Generate image with FLUX 1.1 [pro]
      description: Submits an asynchronous image generation request using the FLUX 1.1 [pro] model, which offers improved prompt adherence and image quality over FLUX.1 [pro]. Returns a task ID and polling URL. The caller must poll GET /v1/get_result?id={id} until the status is Ready, then download the image from the returned sample URL.
      tags:
      - Generation
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FluxProGenerationRequest'
      responses:
        '200':
          description: Generation task accepted. Poll the returned ID for results.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/TaskResponse'
        '400':
          description: Bad request. Invalid parameters.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized. Missing or invalid API key.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '422':
          description: Validation error. Request body failed schema validation.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ValidationErrorResponse'
  /flux-pro:
    post:
      operationId: generateFluxPro
      summary: Generate image with FLUX.1 [pro]
      description: Submits an asynchronous image generation request using the original FLUX.1 [pro] model. Returns a task ID for polling. The pro model delivers high-quality images with strong prompt following and supports a full range of aspect ratios via width and height parameters.
      tags:
      - Generation
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FluxProGenerationRequest'
      responses:
        '200':
          description: Generation task accepted.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/TaskResponse'
        '400':
          description: Bad request.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '422':
          description: Validation error.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ValidationErrorResponse'
  /flux-dev:
    post:
      operationId: generateFluxDev
      summary: Generate image with FLUX.1 [dev]
      description: Submits an asynchronous image generation request using the FLUX.1 [dev] model. The dev model is a distilled version of FLUX.1 [pro] intended for non-commercial use, offering a balance of quality and speed. Requires accepting the FLUX.1 [dev] non-commercial license.
      tags:
      - Generation
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FluxDevGenerationRequest'
      responses:
        '200':
          description: Generation task accepted.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/TaskResponse'
        '400':
          description: Bad request.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '422':
          description: Validation error.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ValidationErrorResponse'
  /flux-schnell:
    post:
      operationId: generateFluxSchnell
      summary: Generate image with FLUX.1 [schnell]
      description: Submits an asynchronous image generation request using the FLUX.1 [schnell] model. Schnell is the fastest FLUX variant, optimized for local development and personal use. It typically requires only 1-4 inference steps and returns results faster than other variants.
      tags:
      - Generation
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FluxSchnellGenerationRequest'
      responses:
        '200':
          description: Generation task accepted.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/TaskResponse'
        '400':
          description: Bad request.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '422':
          description: Validation error.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ValidationErrorResponse'
  /flux-pro-1.1-ultra:
    post:
      operationId: generateFluxPro11Ultra
      summary: Generate image with FLUX 1.1 [pro] Ultra
      description: Submits an image generation request using the FLUX 1.1 [pro] Ultra model, which supports higher resolution outputs up to 4 megapixels and includes an optional raw mode for more photorealistic results. Returns a task ID for polling.
      tags:
      - Generation
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/FluxUltraGenerationRequest'
      responses:
        '200':
          description: Generation task accepted.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/TaskResponse'
        '400':
          description: Bad request.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '422':
          description: Validation error.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ValidationErrorResponse'
components:
  schemas:
    TaskResponse:
      type: object
      description: Response returned when an image generation task is accepted. Contains the task ID and a polling URL for checking status.
      properties:
        id:
          type: string
          format: uuid
          description: Unique identifier for the generation task. Use this ID to poll GET /v1/get_result for the result.
        polling_url:
          type: string
          format: uri
          description: Convenience URL for polling the result. Equivalent to GET /v1/get_result?id={id}.
    ErrorResponse:
      type: object
      description: Error response returned when a request fails.
      properties:
        detail:
          type: string
          description: Human-readable error message describing the failure.
        status_code:
          type: integer
          description: HTTP status code.
    FluxProGenerationRequest:
      type: object
      description: Request body for FLUX.1 [pro] and FLUX 1.1 [pro] image generation. Specifies the prompt, image dimensions, output format, and model quality parameters.
      required:
      - prompt
      properties:
        prompt:
          type: string
          description: Text description of the image to generate. Detailed, descriptive prompts generally yield better results.
          maxLength: 10000
        width:
          type: integer
          description: Width of the generated image in pixels. Must be a multiple of 32. Defaults to 1024.
          minimum: 256
          maximum: 1440
          default: 1024
        height:
          type: integer
          description: Height of the generated image in pixels. Must be a multiple of 32. Defaults to 768.
          minimum: 256
          maximum: 1440
          default: 768
        steps:
          type: integer
          description: Number of diffusion steps. Higher values produce better quality but take longer. Defaults vary by model.
          minimum: 1
          maximum: 50
        guidance:
          type: number
          description: Classifier-free guidance scale. Higher values follow the prompt more closely but may reduce image naturalness.
          minimum: 1.5
          maximum: 5.0
          default: 3.5
        seed:
          type: integer
          description: Random seed for reproducible generation. If omitted, a random seed is used.
          minimum: 0
        safety_tolerance:
          type: integer
          description: Content safety filter tolerance level from 0 (most strict) to 6 (least strict). Default is 2.
          minimum: 0
          maximum: 6
          default: 2
        output_format:
          type: string
          description: Output image format.
          enum:
          - jpeg
          - png
          default: jpeg
        prompt_upsampling:
          type: boolean
          description: If true, automatically enhances the prompt before generation using an LLM to improve image quality and prompt adherence.
          default: false
    FluxUltraGenerationRequest:
      type: object
      description: Request body for FLUX 1.1 [pro] Ultra image generation. Supports higher resolution outputs and an optional raw mode for photorealistic results without additional artistic processing.
      required:
      - prompt
      properties:
        prompt:
          type: string
          description: Text description of the image to generate.
          maxLength: 10000
        aspect_ratio:
          type: string
          description: Aspect ratio of the generated image. Ultra uses aspect ratios instead of explicit width/height.
          enum:
          - '21:9'
          - '16:9'
          - '4:3'
          - '3:2'
          - '1:1'
          - '2:3'
          - '3:4'
          - '9:16'
          - '9:21'
          default: '16:9'
        seed:
          type: integer
          description: Random seed for reproducibility.
          minimum: 0
        safety_tolerance:
          type: integer
          description: Safety filter tolerance (0-6).
          minimum: 0
          maximum: 6
          default: 2
        output_format:
          type: string
          description: Output image format.
          enum:
          - jpeg
          - png
          default: jpeg
        raw:
          type: boolean
          description: If true, generates more natural, less processed images with a more photorealistic aesthetic.
          default: false
    ValidationErrorResponse:
      type: object
      description: Validation error response returned when the request body fails schema validation.
      properties:
        detail:
          type: array
          description: Array of validation error details.
          items:
            type: object
            properties:
              loc:
                type: array
                description: Location of the validation error in the request.
                items:
                  oneOf:
                  - type: string
                  - type: integer
              msg:
                type: string
                description: Validation error message.
              type:
                type: string
                description: Error type identifier.
    FluxSchnellGenerationRequest:
      type: object
      description: Request body for FLUX.1 [schnell] image generation. Schnell is optimized for speed with fewer inference steps required.
      required:
      - prompt
      properties:
        prompt:
          type: string
          description: Text description of the image to generate.
          maxLength: 10000
        width:
          type: integer
          description: Width of the generated image in pixels.
          minimum: 256
          maximum: 1440
          default: 1024
        height:
          type: integer
          description: Height of the generated image in pixels.
          minimum: 256
          maximum: 1440
          default: 768
        steps:
          type: integer
          description: Number of inference steps. Schnell typically uses 1-4 steps.
          minimum: 1
          maximum: 12
          default: 4
        seed:
          type: integer
          description: Random seed for reproducibility.
          minimum: 0
        safety_tolerance:
          type: integer
          description: Safety filter tolerance (0-6).
          minimum: 0
          maximum: 6
          default: 2
        output_format:
          type: string
          description: Output image format.
          enum:
          - jpeg
          - png
          default: jpeg
    FluxDevGenerationRequest:
      type: object
      description: Request body for FLUX.1 [dev] image generation. Similar to the pro request but with parameters tuned for the distilled dev model.
      required:
      - prompt
      properties:
        prompt:
          type: string
          description: Text description of the image to generate.
          maxLength: 10000
        width:
          type: integer
          description: Width of the generated image in pixels.
          minimum: 256
          maximum: 1440
          default: 1024
        height:
          type: integer
          description: Height of the generated image in pixels.
          minimum: 256
          maximum: 1440
          default: 768
        steps:
          type: integer
          description: Number of diffusion inference steps.
          minimum: 1
          maximum: 50
          default: 28
        guidance:
          type: number
          description: Guidance scale for prompt adherence.
          minimum: 1.5
          maximum: 5.0
          default: 3.5
        seed:
          type: integer
          description: Random seed for reproducibility.
          minimum: 0
        safety_tolerance:
          type: integer
          description: Safety filter tolerance (0-6).
          minimum: 0
          maximum: 6
          default: 2
        output_format:
          type: string
          description: Output image format.
          enum:
          - jpeg
          - png
          default: jpeg
  securitySchemes:
    apiKeyAuth:
      type: apiKey
      in: header
      name: X-Key
      description: API key from the Black Forest Labs developer portal. Pass in the X-Key header for all authenticated requests.
externalDocs:
  description: Flux Kontext Image Editing Documentation
  url: https://docs.bfl.ml/kontext/kontext_image_editing