Start creating

FLUX.2 [klein] 4BAI image generator

The smallest, fastest FLUX.2, for volume. On Leap, it sits beside 174 other models in one studio.

  • Text to image
  • 9 aspect ratios

Your first image is free. 1 image on FLUX.2 [klein] 4B: $0.019. Your words wait while you sign in.

  • No subscription
  • Every top model, one account
  • Pay per run, priced before it starts
A sketchbook desk with a tangerine, a real run on Leap
A sketchbook desk with a tangerine

AI image generator

FLUX.2 [klein] 4B at a glance

FLUX.2 [klein] 4B is an image model from Black Forest Labs. It makes images from words.

Made by
Black Forest Labs
Makes
Images
Starts from
Words
Shapes
1:1, 3:2, 2:3, 4:3, 3:4, 16:9, 9:16, 21:9, 9:21
Per run
Up to 4 images
Prompt
Up to 4,000 characters
Price per run
$0.019
Run time
About 3 seconds
Updated
October 2, 2026
  1. 01Describe what you want to see
  2. 02See the exact price, then press go
  3. 03Keep it in your library, or take it further

Made on Leap

More from FLUX.2 [klein] 4B

  • FLUX.2 [klein] 4B's answer to the same prompt: a ramen bar sign reading OPEN LATE on a rainy night

    A hand-painted shop sign that reads OPEN LATE above a tiny ramen bar on a rainy night, warm light spilling onto wet cobblestones, cinematic 35mm photo

Pick the right one

FLUX.2 [klein] 4B and its siblings

ModelBest forPrice per run
FLUX.2 [klein] 4B (this page)The smallest, fastest FLUX.2, for volume.$0.019
FLUX.1 [schnell]Fast, low-cost text to image. Good for drafts and volume.$0.006
FLUX.2 [pro]Black Forest Labs' second generation: sharper detail and text than FLUX1.1, at a lower price.$0.041
FLUX.2 [flex]FLUX.2 tuned for typography and fine detail, such as posters and layouts.$0.068

Side by side

More image models on Leap

No prompt needed

Or start from a recipe

Recipes write the prompt for you: add a photo, pick a look, and get a finished result.

Every recipe

Why Leap

Why creators make it on Leap

  1. 01

    Every top model, side by side

    175 models from Black Forest Labs, Google, ByteDance, Kuaishou, Alibaba and more, side by side in one studio.

    See the models
  2. 02

    One click, or full control

    Character Studio, effects and recipes write the prompt for you. Or write your own for any model.

    See the tools
  3. 03

    Your work stays yours

    Everything you make stays in your library while your account is active, and you own what you make here.

    See what people make
  4. 04

    One balance for everything

    The studio, the API and your agents spend the same balance, and every run shows its price before it starts.

    How pricing works

Questions

FLUX.2 [klein] 4B, answered

What is FLUX.2 [klein] 4B?
FLUX.2 [klein] 4B is an image model from Black Forest Labs. The smallest, fastest FLUX.2, for volume. On Leap it runs in one studio beside every other top model, with one account.
What resolution and sizes does it make?
1:1, 3:2, 2:3, 4:3, 3:4, 16:9, 9:16, 21:9 or 9:21.
How is it different from FLUX.1 [schnell], FLUX.2 [pro] and FLUX.2 [flex]?
FLUX.2 [klein] 4B: The smallest, fastest FLUX.2, for volume. FLUX.1 [schnell]: Fast, low-cost text to image. Good for drafts and volume. FLUX.2 [pro]: Black Forest Labs' second generation: sharper detail and text than FLUX1.1, at a lower price. FLUX.2 [flex]: FLUX.2 tuned for typography and fine detail, such as posters and layouts. They all run in the same studio, so you can try one prompt on each.
How much does a run cost?
An image costs $0.019. You see the exact price before you press go, and a run that fails costs nothing.
Is FLUX.2 [klein] 4B free to try?
No. There is no free credit: you add credit from $5, and your first top-up has no card fee. The cheapest run is $0.019 (an image), so $5 covers 263 of those. You pay per run, in dollars, with no subscription.
Can I use what I make commercially?
Yes. You own what you make on Leap, so you can use it commercially, and we never train AI on it. The people and brands shown in a result can still have rights in it; the Terms say more.
Is there an API?
Yes. Leap's REST API runs it as black-forest-labs/flux-2-klein-4b, at the same price per run as the studio, and agents can call it through Leap's MCP server. The request is at the bottom of this page.
Do I need a Black Forest Labs account?
No. Leap sends your request to Black Forest Labs' model and gives you what it makes. One Leap account runs FLUX.2 [klein] 4B and every other model, in the studio, through the API and from your agents.

Your idea, FLUX.2 [klein] 4B.

Every run shows its price before it starts, and one that fails costs nothing.

Make it with FLUX.2 [klein] 4B

For developers

Run FLUX.2 [klein] 4B from code

API docs
Model ID
black-forest-labs/flux-2-klein-4b
Makes
Image
Pricing
Per run, quoted first: POST /v1/quotes

Inputs

What the model takes. Leave out anything with a default.

Promptprompt
Text, up to 4,000 characters, required
Aspect ratioaspect_ratio
1:1, 3:2, 2:3, 4:3, 3:4, 16:9, 9:16, 21:9, 9:21. Default: 1:1
Imagesn
1 to 4. Default: 1
Seedseed
0 to 4294967295The same seed and input give the same image.

The request

The same envelope for every model; only the model and its input change. With prefer: wait=60 the answer holds the result when the run finishes within a minute; a longer one is read again by its ID. Agents can call it through the MCP server at app.tryleap.ai/api/mcp.

curl https://api.tryleap.ai/v1/generations \  -H "x-api-key: $LEAP_API_KEY" \  -H "content-type: application/json" \  -H "prefer: wait=60" \  -d '{    "model": "black-forest-labs/flux-2-klein-4b",    "input": {      "prompt": "A paper boat drifting down a rainy street at dusk"    }  }' # Video often outlasts the wait and answers "queued" or "running".# Put its "id" in GENERATION_ID and read it again until it is done:# curl https://api.tryleap.ai/v1/generations/$GENERATION_ID -H "x-api-key: $LEAP_API_KEY"