FLUX.1 [dev]

Name: FLUX.1 [dev]
Brand: Black Forest Labs
Price: 0.025 USD
Availability: InStock

AI Image Generation Model

Image

Black Forest Labs' 12-billion parameter flow transformer for high-quality text-to-image generation, suitable for personal and commercial use with streaming support

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2048 x 2048

Max Resolution

Supported Modes

Text to Image Image Edit

Active

Details

Model ID

flux.1-dev

Also known as: flux-dev

Creator

Black Forest Labs

Family

flux.1

Ready to integrate?

Access flux.1-dev via our unified API.

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Available at 2 providers

Starting from

$0.025 /image via fal.ai, Replicate

Prices shown are in USD

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Providers & Pricing (2)

FLUX.1 [dev] is available from 2 providers, with per-image pricing starting at $0.025 through fal.ai.

fal.ai

Text to Image

fal/flux.1-dev

Provider Model ID: fal-ai/flux/dev

$0.025 /image

View pricing details

Replicate

Text to Image Image Edit

replicate/flux.1-dev

Provider Model ID: black-forest-labs/flux-dev

$0.025 /image

View pricing details

flux-dev API OpenAI-compatible

Lumenfall provides an OpenAI-compatible API to integrate FLUX.1 [dev] for high-fidelity text-to-image generation and streaming media workflows.

Base URL

https://api.lumenfall.ai/openai/v1

Model

flux.1-dev

Code Examples

Text to Image

/v1/images/generations

curl -X POST \

  https://api.lumenfall.ai/openai/v1/images/generations \

  -H "Authorization: Bearer $LUMENFALL_API_KEY" \

  -H "Content-Type: application/json" \

  -d '{

    "model": "flux.1-dev",

    "prompt": "",

    "size": "1024x1024"

}'

# Response:

# { "created": 1234567890, "data": [{ "url": "https://...", "revised_prompt": "..." }] }

import OpenAI from 'openai';

const client = new OpenAI({

  apiKey: 'YOUR_API_KEY',

  baseURL: 'https://api.lumenfall.ai/openai/v1'

});

const response = await client.images.generate({

  model: 'flux.1-dev',

  prompt: '',

  size: '1024x1024'

});

// { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }

console.log(response.data[0].url);

from openai import OpenAI

client = OpenAI(

    api_key="YOUR_API_KEY",

    base_url="https://api.lumenfall.ai/openai/v1"

response = client.images.generate(

    model="flux.1-dev",

    prompt="",

    size="1024x1024"

# { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }

print(response.data[0].url)

Image Edit

/v1/images/edits

curl -X POST \

  https://api.lumenfall.ai/openai/v1/images/edits \

  -H "Authorization: Bearer $LUMENFALL_API_KEY" \

  -F "model=flux.1-dev" \

  -F "[email protected]" \

  -F "prompt=Add a starry night sky to this image" \

  -F "size=1024x1024"

# Response:

# { "created": 1234567890, "data": [{ "url": "https://...", "revised_prompt": "..." }] }

import OpenAI from 'openai';

import fs from 'fs';

const client = new OpenAI({

  apiKey: 'YOUR_API_KEY',

  baseURL: 'https://api.lumenfall.ai/openai/v1'

});

const response = await client.images.edit({

  model: 'flux.1-dev',

  image: fs.createReadStream('source.png'),

  prompt: 'Add a starry night sky to this image',

  size: '1024x1024'

});

// { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }

console.log(response.data[0].url);

from openai import OpenAI

client = OpenAI(

    api_key="YOUR_API_KEY",

    base_url="https://api.lumenfall.ai/openai/v1"

response = client.images.edit(

    model="flux.1-dev",

    image=open("source.png", "rb"),

    prompt="Add a starry night sky to this image",

    size="1024x1024"

# { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }

print(response.data[0].url)

Parameter Reference

Required Supported Not available

Core Parameters

Parameter	Type	Description	Modes
`prompt`	string	Required. Text prompt for image generation	T2I Edit
`seed`	integer	Random seed for reproducibility	T2I Edit

Size & Layout

Parameter	Type	Description	Modes
`size`	string	Image dimensions as WxH pixels (e.g. "1024x1024") or aspect ratio (e.g. "16:9") WxH determines both shape and scale (aspect_ratio and resolution are ignored when size is provided). W:H format is equivalent to aspect_ratio.	T2I Edit
`aspect_ratio`	string	Aspect ratio of the output image (e.g. "16:9", "1:1") Controls shape independently of scale. Use with resolution to control both. If size is also provided, size takes precedence. Any ratio is accepted and mapped to the nearest supported value.	T2I Edit
`resolution`	string	Output resolution tier (e.g. "1K", "4K") `1K` Controls scale independently of shape. Higher tiers produce larger images and cost more. If size is also provided, size takes precedence for scale. Any tier is accepted and mapped to the nearest supported value.	T2I Edit

Output	`size`		`aspect_ratio` + `resolution`
Flexible
Custom 1–14142px per side	`"WxH"`	—	Any pixel dimensions within model constraints

1K 11 sizes

Output	`size`		`aspect_ratio` + `resolution`
1183 × 887	`"1183x887"`	or	`"4:3"` + `"1K"`
916 × 1145	`"916x1145"`	or	`"4:5"` + `"1K"`
1145 × 916	`"1145x916"`	or	`"5:4"` + `"1K"`
1024 × 1024	`"1024x1024"`	or	`"1:1"` + `"1K"`
887 × 1182	`"887x1182"`	or	`"3:4"` + `"1K"`
836 × 1254	`"836x1254"`	or	`"2:3"` + `"1K"`
1254 × 836	`"1254x836"`	or	`"3:2"` + `"1K"`
768 × 1365	`"768x1365"`	or	`"9:16"` + `"1K"`
1365 × 768	`"1365x768"`	or	`"16:9"` + `"1K"`
670 × 1564	`"670x1564"`	or	`"9:21"` + `"1K"`
1563 × 670	`"1563x670"`	or	`"21:9"` + `"1K"`

How these parameters work

size

Exact pixel dimensions

"1920x1080"

aspect_ratio

Shape only, default scale

"16:9"

resolution

Scale tier, preserves shape

"1K"

Priority when combined

size › aspect_ratio + resolution › aspect_ratio › resolution

size is most specific and always wins. aspect_ratio and resolution control shape and scale independently.

How matching works

Shape matching – we pick the closest supported ratio. Ask for 7:1 on a model with 4:1 and 8:1, you get 8:1.

Scale matching – providers use different tier formats: K tiers (0.5K 1K 2K 4K) or megapixel tiers (0.25 1). If the exact tier isn't available, you get the nearest one.

Dimension clamping – if a model has pixel limits, we clamp dimensions to fit and keep the aspect ratio intact.

Media Inputs

Parameter	Type	Description	Modes
`image`	file	Required. Input image(s) to edit Supports PNG, JPEG, WebP.	T2I Edit

Output & Format

Parameter	Type	Description	Modes
`response_format`	string	How to return the image `url` `b64_json` Default: `"url"`	T2I Edit
`output_format`	string	Output image format `png` `jpeg` `gif` `webp` `avif` Gateway converts to requested format if provider doesn't support it natively.	T2I Edit
`output_compression`	integer	Compression level for lossy formats (JPEG, WebP, AVIF)	T2I Edit
`n`	integer	Number of images to generate Default: `1` Gateway generates multiple images in parallel even if provider only supports 1.	T2I Edit

Additional Parameters

Parameter	Type	Description	Modes
`cfg_scale`	number	Classifier-free guidance scale — higher values stick more closely to the prompt	T2I Edit
`strength`	number	How much to transform the input image: 0 keeps it unchanged, 1 fully regenerates from the prompt	T2I Edit
`acceleration` fal	string	The speed of the generation. The higher the speed, the faster the generation. `high` `none` `regular`	T2I Edit
`disable_safety_checker` replicate	boolean	Disable safety checker for generated images.	T2I Edit
`enable_safety_checker` fal	boolean	If set to true, the safety checker will be enabled.	T2I Edit
`go_fast` replicate	boolean	Run faster predictions with model optimized for speed (currently fp8 quantized); disable to run in original bf16. Note that outputs will not be deterministic when this is enabled, even if you set a seed.	T2I Edit
`megapixels` replicate	string	Approximate number of megapixels for generated image `0.25` `1`	T2I Edit
`num_inference_steps`	integer	The number of inference steps to perform.	T2I Edit
`output_quality` replicate	integer	Quality when saving the output images, from 0 to 100. 100 is best quality, 0 is lowest quality. Not relevant for .png outputs	T2I Edit
`sync_mode` fal	boolean	If `True`, the media will be returned as a data URI and the output data won't be available in the request history.	T2I Edit

Parameter Normalization

How we handle parameters across different providers

Not every provider speaks the same language. When you send a parameter, we handle it in one of four ways depending on what the model supports:

Behavior	What happens	Example
`passthrough`	Sent as-is to the provider	style, quality
`renamed`	Same value, mapped to the field name the provider expects	prompt
`converted`	Transformed to the provider's native format	size
`emulated`	Works even if the provider has no concept of it	n, response_format

Parameters we don't recognize pass straight through to the upstream API, so provider-specific options still work.

Full API Reference Authentication, endpoints, and more

Gallery

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FLUX.1 [dev] FAQ

How much does FLUX.1 [dev] cost?

FLUX.1 [dev] starts at $0.025 per image through Lumenfall. Pricing varies by provider. Lumenfall does not add any markup to provider pricing.

How do I use FLUX.1 [dev] via API?

You can use FLUX.1 [dev] through Lumenfall's OpenAI-compatible API. Send requests to the unified endpoint with model ID "flux.1-dev". Code examples are available in Python, JavaScript, and cURL.

Which providers offer FLUX.1 [dev]?

FLUX.1 [dev] is available through fal.ai and Replicate on Lumenfall. Lumenfall automatically routes requests to the best available provider.

What is the maximum resolution for FLUX.1 [dev]?

FLUX.1 [dev] supports images up to 2048x2048 resolution.

Overview

FLUX.1 [dev] is a 12-billion parameter text-to-image synthesis model developed by Black Forest Labs. As an open-weight model derived from the FLUX.1 [pro] architecture, it is designed for high-fidelity image generation while remaining accessible for non-commercial development. It is distinguished by its use of flow matching, which allows it to generate images with higher composition quality and structural integrity than traditional diffusion-based models of similar size.

Strengths

Precise Text Rendering: The model excels at following complex prompts requiring the inclusion of specific text, exhibiting high character accuracy and legibility in generated signs, labels, and documents.
Anatomical Accuracy: It shows a significant reduction in common AI artifacts, such as distorted hands or inconsistent limb counts, producing more anatomically correct human figures.
Prompt Adherence: The architecture is highly responsive to detailed, long-form descriptions, maintaining high fidelity to nuanced instructions regarding lighting, camera angles, and object placement.
Visual Variety: It is capable of generating a wide range of styles, from photorealistic portraits to stylized digital art, without requiring extensive LoRA fine-tuning for basic aesthetic changes.

Limitations

Hardware Requirements: With 12 billion parameters, the model is computationally heavy; running it locally requires substantial VRAM (typically 24GB or more) compared to smaller models like Stable Diffusion XL.
Inference Speed: While it supports streaming, the generation process is inherently slower than “schnell” or distilled versions of the same family due to the higher step count required for optimal results.
Licensing Constraints: Unlike the [schnell] variant, the [dev] model is released under a non-commercial license, which may limit its direct use in some production environments without a commercial agreement.

Technical Background

FLUX.1 [dev] is built on a flow-based transformer architecture. Rather than relying on standard latent diffusion, it utilizes flow matching—a method that learns a vector field to map a simple noise distribution to the target data distribution. This approach, combined with its high parameter count, allows the model to capture more complex spatial relationships and finer details during the sampling process.

Best For

This model is best suited for developers building high-end creative tools, designers requiring precise typography within images, and researchers exploring the limits of flow-matching models. It is an ideal choice for tasks where image quality and prompt accuracy are more critical than raw generation speed. FLUX.1 [dev] is available for testing and integration through Lumenfall’s unified API and interactive playground.

Try FLUX.1 [dev] in Playground

Generate images with custom prompts — no API key needed.

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