FLUX.1 [dev]

Image generationAvailable
by Black Forest LabsModel ID: flux-1-dev

The open-weight 12B rectified-flow transformer from Black Forest Labs. Close to FLUX Pro quality with a guidance-distilled checkpoint released under a non-commercial license. The most widely fine-tuned base in the FLUX family.

Price
US$0.030/image
Aspect ratios
1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3
Input β†’ output
Text β†’ Image
Developer
Black Forest Labs
Updated
23 September 2026
01

Playground

Try FLUX.1 [dev]

Input & output

US$0.030/image
Try FLUX.1 [dev]

0 / 2,000

What to generate

Advanced settings (4)

Optional seed for reproducibility

Output
Your image appears here.

This run

US$0.03 Β· 3 credits

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

New here?

10 free credits (US$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.

02

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.
  • Example output 1 from FLUX.1 [dev]: black forest gateau cake spelling out the words "FLUX DEV", tasty, food photography, dynamic shotOpen full size

    Prompt

    black forest gateau cake spelling out the words "FLUX DEV", tasty, food photography, dynamic shot

    Settings

    aspect_ratio
    1:1
  • Example output 2 from FLUX.1 [dev]: Three magical wizards standing on a yellow table, each holding a sign. On the left, a wizard in black robes holds a sign that says β€˜AI’; in Open full size

    Prompt

    Three magical wizards standing on a yellow table, each holding a sign. On the left, a wizard in black robes holds a sign that says β€˜AI’; in the middle, a witch in red robes holds a sign that says β€˜is’; and on the right, a wizard in blue robes holds a sign that says β€˜cool’

    Settings

    aspect_ratio
    1:1
  • Example output 3 from FLUX.1 [dev]: a cat holding a sign that says hello worldOpen full size

    Prompt

    a cat holding a sign that says hello world

    Settings

    aspect_ratio
    1:1
03

About FLUX.1 [dev]

TL;DRAs of 23 September 2026

FLUX.1 [dev] is a model by Black Forest Labs in the Image generation category. On Railwail, FLUX.1 [dev] costs US$0.030 per image. Supported aspect ratios: 1:1, 16:9, 9:16, 4:3, 3:4, 3:2 and 2:3.

FLUX.1 [dev] is the openly released variant of FLUX, a 12 billion parameter flow-matching transformer. It trades a little quality versus the Pro endpoints for open weights, which is why it is the standard base for community LoRAs and fine-tunes. Supports guidance scale and configurable inference steps for quality-versus-speed tuning.
04

Pricing

Prices in US dollars. Usage is charged from prepaid credits.
Per imageUS$0.030 per image
  • 1 credit = US$0.01

Cost calculator

Price calculator

/ run

Total

US$3.00

300 credits

Per run

US$0.03 Β· 3 credits

Fixed price per run, known before the run starts.

05

API

Call FLUX.1 [dev] with your Railwail API key. Use this model ID in the request:
curl https://railwail.com/api/v1/images/generations \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "flux-1-dev",
    "prompt": "A lighthouse on a rocky coast at sunset, photorealistic"
  }'
Set your key as RAILWAIL_API_KEYCreate API key
06

Specifications

Model ID
flux-1-dev
Input
Text
Output
Image
Output formats
WEBP, PNG, JPG
Aspect ratios
1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3
Billing
Fixed price, known before the run
Catalog entry updated
23 September 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.

  • seed

    Optional seed for reproducibility

    Type: Integer
    Default: –
    Allowed values: –
  • prompt

    What to generate

    Type: Text
    Default: –
    Allowed values: up to 2,000 characters
  • guidance
    Type: Number
    Default: 3.5
    Allowed values: 0 to 10
  • aspect_ratio
    Type: Choice
    Default: 1:1
    Allowed values: 1:1, 16:9, 9:16, 4:3, 3:4, 3:2 or 2:3
  • output_format
    Type: Choice
    Default: webp
    Allowed values: webp, png or jpg
  • num_inference_steps
    Type: Integer
    Default: 28
    Allowed values: 1 to 50

Tags

  • replicate
  • flux
  • black-forest-labs
  • text-to-image
  • open-weights
  • flagship
07

Use cases

08

Frequently asked questions

What is FLUX.1 [dev]?

FLUX.1 [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.1 [dev] cost on Railwail?

On Railwail, FLUX.1 [dev] costs US$0.030 per image. The price is known before the run starts. Usage is paid from prepaid credits; 1 credit equals US$0.01.

Which settings does FLUX.1 [dev] support?

According to its input schema, FLUX.1 [dev] knows these parameters: seed, prompt (up to 2,000 characters), guidance (0 to 10), aspect_ratio (1:1, 16:9, 9:16, 4:3, 3:4, 3:2 or 2:3), output_format (webp, png or jpg) and num_inference_steps (1 to 50).

How fast is FLUX.1 [dev]?

There are not enough measured runs of FLUX.1 [dev] on Railwail yet to state a run time. It depends on the input, the settings and the load at the provider.

Is FLUX.1 [dev] better than FLUX 1.1 Pro?

That depends on the task. FLUX.1 [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.1 [dev] and FLUX 1.1 Pro

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

Create a Railwail API key and send your request with the model ID flux-1-dev. Code examples for curl, Python and JavaScript are in the API section of this page.

09

Comparable models

All in this category

Use FLUX.1 [dev] via the API

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