Flux Dev

Name: Flux Dev
Brand: Black Forest Labs
SKU: flux-dev
Price: 0.0384 USD
Availability: InStock

Image generationAvailable

by Black Forest Labsflux-dev

Black Forest Labs' development model. Fast, high-quality image generation with LoRA support.

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Price: $0.0384/image
Aspect ratios: 1:1, 16:9, 9:16, 3:2, 2:3, 4:5, 5:4
Input → output: Text → Image
Developer: Black Forest Labs
Updated: September 23, 2026

Playground

Try Flux Dev

Input & output

$0.0384/image

Prompt

Aspect ratio(optional)

Advanced settings (1)

Output format(optional)

⌘/Ctrl + Enter

Output

Your image appears here.

This run

$0.0384 · 3.84 credits

For accounts without a purchase: runs above 2 credits need a top-up.

New here?

10 free credits ($0.10) when you sign up with Google

Usable 24 hours after sign-up, up to 5 runs per day and at most 2 credits per run. Other sign-in methods start without credits.

Examples

Real outputs from the public examples of this model on Replicate, with the prompt and settings that produced them. They were not generated live on this page.

Open full size
Prompt
style of 80s cyberpunk, a portrait photo
Settings
aspect_ratio

1:1
Open full size
Prompt
pnt style Illustration of a latina woman
Settings
aspect_ratio

1:1
Open full size
Prompt
A tabby cat lounging on a sun-dappled windowsill, half its body in shadow, half in bright light, flmft style
Settings
aspect_ratio

1:1

Example prompts

Examples from the Railwail catalog. They were not generated live on this page.

Landscape
A serene mountain lake at golden hour, with snow-capped peaks reflected perfectly in the still water, pine forests lining the shore, warm amber light casting long shadows across the meadow
Character Design
A cyberpunk street samurai with neon-blue cybernetic arm, wearing a weathered leather jacket, standing in a rain-soaked Tokyo alley with holographic signs reflecting in puddles
Still Life
An elegant flat lay arrangement of artisan coffee beans, a brass hand grinder, a ceramic pour-over dripper, and fresh croissants on a dark walnut table, morning light streaming from the left

About Flux Dev

TL;DRAs of September 23, 2026

Flux Dev is a model by Black Forest Labs in the Image generation category. On Railwail, Flux Dev costs $0.0384 per image. Supported aspect ratios: 1:1, 16:9, 9:16, 3:2, 2:3, 4:5, and 5:4.

Background

About Black Forest Labs

Founded 2024 · Freiburg, Germany

Black Forest Labs was founded in August 2024 by Robin Rombach, Patrick Esser, Andreas Blattmann and Dominik Lorenz, the original Latent Diffusion and Stable Diffusion team from LMU Munich and Stability AI. Headquartered in Freiburg, Germany, the lab raised a $31M seed round led by Andreessen Horowitz and launched the FLUX.1 family in August 2024 with three tiers: FLUX.1 [pro] (closed, API-only, highest quality), FLUX.1 [dev] (open weights, non-commercial, near-pro quality) and FLUX.1 [schnell] (open weights Apache 2.0, distilled few-step).

Visit Black Forest Labs

Architecture

Rectified-flow Diffusion Transformer (DiT)

FLUX.1 [dev] is the open-weights research variant of the FLUX.1 family, providing near-FLUX.1 [pro] quality with publicly downloadable weights. The architecture is a rectified-flow Diffusion Transformer (DiT) with approximately 12B parameters, trained with the flow-matching objective from the SD3 paper (Esser et al. 2024). It uses T5-XXL plus CLIP-L as parallel text encoders, allowing both long descriptive prompts and short keyword-style prompts. Image tokens come from a learned 16x latent VAE. Sampling typically uses 28-50 flow-matching steps with the Euler sampler at guidance ~3.5. FLUX.1 [dev] is guidance-distilled from a teacher and uses 'guidance' as a conditioning input rather than classifier-free guidance at inference, simplifying multi-step deployment. The model produces images up to 2 MP with strong prompt adherence, photorealistic detail and notably good in-image text rendering.

Parameters: ~12B parameters
Context: 512 tokens

Capabilities

Near-state-of-the-art photorealism for an open model
Up to 2 MP output resolution (1MP standard)
Strong prompt adherence via T5-XXL
Good in-image text rendering (short strings)
Open weights — self-hostable, fine-tunable
ControlNet, LoRA and IP-Adapter ecosystem
Compatible with FLUX Tools (Fill, Canny, Depth, Redux)
Best for: self-hosted creative pipelines, custom fine-tunes, research, ControlNet workflows.

Training & license

Pretrained on a large licensed and publicly available image-text dataset; then distilled from a teacher to produce the [dev] guidance-distilled checkpoint. Exact composition and token counts are not disclosed.

License: FLUX.1 [dev] Non-Commercial License — free for research and personal use; commercial use requires a separate agreement with Black Forest Labs.

Safety testing: Baseline safety filters at the API tier; the open weights ship without an integrated safety classifier and operators are expected to add their own moderation.

Known limitations

Non-commercial license restricts production use
Lower quality than FLUX.1 [pro] on fine details
Slow on consumer GPUs without quantisation
Hands and complex small text still imperfect

Research papers

Pricing

Prices in US dollars. Usage is charged from prepaid credits.

Per image	$0.0384 per image

1 credit = $0.01

Cost calculator

Price calculator

Results per run

/ run

Runs

Total

$3.84

384 credits

Per run

$0.0384 · 3.84 credits

Fixed price per run, known before the run starts.

API

Call Flux Dev with your Railwail API key. Use this model ID in the request:

flux-devAPI documentation Get an API key

curl https://railwail.com/api/v1/images/generations \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "flux-dev",
    "prompt": "A lighthouse on a rocky coast at sunset, photorealistic"
  }'

import os
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["RAILWAIL_API_KEY"],
    base_url="https://railwail.com/api/v1",
)

image = client.images.generate(
    model="flux-dev",
    prompt="A lighthouse on a rocky coast at sunset, photorealistic",
)

print(image.data[0].url)

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://railwail.com/api/v1",
});

const image = await client.images.generate({
  model: "flux-dev",
  prompt: "A lighthouse on a rocky coast at sunset, photorealistic"
});

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

// npm install railwail
import railwail from "railwail";

const rw = railwail(process.env.RAILWAIL_API_KEY);

const res = await rw.image("flux-dev", "A lighthouse on a rocky coast at sunset, photorealistic");

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

Set your key as RAILWAIL_API_KEYCreate API key

Specifications

Model ID: flux-dev
Developer: Black Forest Labs
Category: Image generation
Input: Text
Output: Image
Output formats: WEBP, JPG, PNG
Aspect ratios: 1:1, 16:9, 9:16, 3:2, 2:3, 4:5, 5:4
Billing: Fixed price, known before the run
Model size: ~12B parameters
License: FLUX.1 [dev] Non-Commercial License — free for research and personal use; commercial use requires a separate agreement with Black Forest Labs.
Catalog entry updated: September 23, 2026

Input parameters

Inputs and settings from the model's input schema. The example in the API section shows which of them the API accepts.

ParameterTypeDefaultAllowed values

promptrequired
Type: Text
Default: –
Allowed values: –
aspect_ratio
Type: Choice
Default: 1:1
Allowed values: 1:1, 16:9, 9:16, 3:2, 2:3, 4:5, or 5:4
output_format
Type: Choice
Default: webp
Allowed values: webp, jpg, or png

Use cases

What it is used for

Self-hosted creative pipelines
Custom LoRA fine-tunes and brand models
Research and academic experiments
ControlNet and IP-Adapter workflows
Concept art and illustration
Open-source consumer apps (non-commercial)

All models in Image generation

Frequently asked questions

What is Flux Dev?

Flux Dev is a model by Black Forest Labs in the Image generation category. On Railwail you can call it with an API key through the Railwail API.

How much does Flux Dev cost on Railwail?

On Railwail, Flux Dev costs $0.0384 per image. The price is known before the run starts. Usage is paid from prepaid credits; 1 credit equals $0.01.

Which settings does Flux Dev support?

According to its input schema, Flux Dev knows these parameters: prompt, aspect_ratio (1:1, 16:9, 9:16, 3:2, 2:3, 4:5, or 5:4), and output_format (webp, jpg, or png).

How fast is Flux Dev?

There are not enough measured runs of Flux Dev on Railwail yet to state a run time. It depends on the input, the settings and the load at the provider.

Is Flux Dev better than FLUX 1.1 Pro?

That depends on the task. Flux Dev (Black Forest Labs) and FLUX 1.1 Pro (Black Forest Labs) are both models in the Image generation category. The comparison page shows their prices and specifications side by side.

Compare Flux Dev and FLUX 1.1 Pro

How do I use Flux Dev through the API?

Create a Railwail API key and send your request with the model ID flux-dev. Code examples for curl, Python and JavaScript are in the API section of this page.

Comparable models

All in this category

FLUX 1.1 ProBlack Forest Labs
Black Forest Labs' flagship text-to-image model. Faster generation than FLUX.1 Pro at higher prompt adherence, with strong photorealism and reliable spatial composition. Runs as a hosted Replicate model.
$0.048/image
25 % more expensive per unit
Compare Flux Dev vs. FLUX 1.1 Pro
Flux 1.1 Pro UltraBlack Forest Labs
FLUX 1.1 Pro in ultra mode. Up to 4 megapixel images with raw mode for photorealism.
$0.072/image
88 % more expensive per unit
Compare Flux Dev vs. Flux 1.1 Pro Ultra
Google Imagen 4Google DeepMind
Google DeepMind's Imagen 4 text-to-image model, hosted on Replicate. Sharp detail, accurate text rendering, and strong prompt adherence across photographic and illustrated styles. Outputs up to 2K resolution.
$0.048/image
25 % more expensive per unit
Compare Flux Dev vs. Google Imagen 4

Use Flux Dev via the API

One API key for every model on Railwail. Usage is charged from prepaid credits, 1 credit = $0.01.

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