Black Forest LabsFastHigh

FLUX Dev

A 12 billion parameter rectified flow transformer capable of generating images from text descriptions, tuned for open, high-quality experimentation.

58 credits

per call (flat, regardless of num_outputs 1-4)

12B parameter rectified flow transformer

Optional fp8 'go_fast' mode for faster generation

Supports image-to-image via the image parameter

Adjustable inference steps (1-50) and guidance

Up to 4 outputs per call

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Quick Start

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "black-forest-labs/flux-dev",
  "input": {
    "prompt": "black forest gateau cake spelling out the words \"FLUX DEV\", tasty, food photography, dynamic shot",
    "aspect_ratio": "1:1",
    "go_fast": true
  }
}'

Parameters

Parameter	Type	Required	Default	Description
`prompt`	string	Yes	-	Prompt for generated image
`aspect_ratio`	string	No	1:1	Aspect ratio for the generated image 1:116:921:93:22:34:55:43:44:39:169:21
`image`	string	No	-	Input image for image-to-image mode. Output aspect ratio matches this image
`prompt_strength`	number	No	0.8	Prompt strength when using img2img. 1.0 corresponds to full destruction of information in image
`num_outputs`	integer	No	1	Number of outputs to generate (1-4). Billed at the same flat rate regardless of count
`num_inference_steps`	integer	No	28	Number of denoising steps (recommended 28-50). Fewer steps = faster, lower quality
`guidance`	number	No	3	Guidance scale for generated image (0-10)
`seed`	integer	No	-	Random seed. Set for reproducible generation
`output_format`	string	No	webp	Format of the output images webpjpgpng
`output_quality`	integer	No	80	Quality when saving the output images, from 0 to 100. 100 is best quality, 0 is lowest quality. Not relevant for .png outputs
`disable_safety_checker`	boolean	No	false	Disable safety checker for generated images.
`go_fast`	boolean	No	true	Run faster fp8-quantized predictions; disable for original bf16 (non-deterministic when enabled)
`megapixels`	string	No	1	Approximate number of megapixels for generated image 10.25

How to Provide File Input

There are 3 ways to provide files for the image parameter:

Recommended

Direct Upload (Multipart)

Attach files directly to POST /v1/predictions/upload. No separate upload step needed.

curl -X POST "https://api.core.today/v1/predictions/upload" \
  -H "X-API-Key: cdt_your_api_key" \
  -F "model=black-forest-labs/flux-dev" \
  -F 'input={"prompt":"your prompt here"}' \
  -F "file:image=@your_file.png"

Image URL

Pass a publicly accessible URL directly. You can also use file_url from the Storage API.

{
  "model": "black-forest-labs/flux-dev",
  "input": {
    "prompt": "your prompt here",
    "image": "https://example.com/image.jpg"
  }
}

See the File Upload docs for more upload methods including Presigned URLs.

Common Parameters

Common parameters used when calling POST /v1/predictions.

Parameter	Type	Required	Default	Description
`model`	string	Yes	-	Model identifier
`input`	object	Yes	-	Object containing the model-specific parameters from the table above
`output_folder`	string	No	-	Folder path for output files (max 256 chars, '..' not allowed)
`webhook_url`	string	No	-	Webhook URL to call on completion
`is_public`	boolean	No	false	If true, output files are also available via permanent public URLs

Examples

Text-to-Image (Default)

Generate an image from a text prompt with default settings

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "black-forest-labs/flux-dev",
  "input": {
    "prompt": "black forest gateau cake spelling out the words \"FLUX DEV\", tasty, food photography, dynamic shot",
    "aspect_ratio": "1:1",
    "go_fast": true
  }
}'