Black Forest LabsimageFastOperational

FLUX.2 [klein] 4B API

The fastest FLUX.2 — open weights, sub-second, a fraction of a cent

bfl/flux-2-klein-4b/text-to-image bfl/flux-2-klein-4b/edit

FromUp to −95%

$0.0007/img$0.014

per image · 1K

Open in Studio API

Try FLUX.2 [klein] 4B

Runs on your balance at the price shown on the button. Results are saved to your account.

Open full-screen Studio

Prompt*

0/5000

Aspect ratio

Output image shape.

Resolution

1K ≈ 1 MP; 2K ≈ 4 MP (long side up to 2048 px).

Estimated cost…

Create a free account with Google or email — pay only for what you generate.

Your image will appear here

Write a prompt, pick your settings and hit Run. You only pay for successful generations.

What is FLUX.2 [klein] 4B?

FLUX.2 [klein] 4B is Black Forest Labs' small, open (Apache-2.0) FLUX.2 model: sub-second text-to-image and editing with up to 4 reference images, at a fraction of a cent per image.

Sub-second

4-step distilled

Fraction of a cent

Per 1 MP image

4 references

Image editing

Open weights

Apache-2.0

Real-time FLUX

klein 4B distills FLUX.2 into 4 steps, so images come back in well under a second — for live previews, batch jobs and interactive apps.

Edits too

Give it up to 4 reference images and describe the change; the output follows the input image.

FLUX.2 [klein] 4B pricing

Pay per image. No subscription. Failed generations are refunded automatically.

Tier	Official price	Cheaper Gen.	You save
1K ≈1 MP	~~$0.014~~/img	$0.0007/img	−95%
2K ≈4 MP	~~$0.017~~/img	$0.0027/img	−84%

Official price: BFL API list price for FLUX.2 [klein] 4B ($0.014 for the first output megapixel, $0.001 per additional MP; input images at $0.001 / MP). Prices verified 2026-10-16.

Specifications

Resolutions: 1K (≈1 MP) · 2K (≈4 MP)
Aspect ratios: 1:1 · 4:3 · 3:4 · 16:9 · 9:16 · 3:2 · 2:3
Edit inputs: Up to 4 images
Weights: Open (Apache-2.0)
Released: Jan 15, 2026

Use FLUX.2 [klein] 4B via API

One request to start a job, one to fetch the result. Same shape for every model.

Full API reference

import os, time, requests

API = "https://cheapergen.com/api/v1"
headers = {"Authorization": f"Bearer {os.environ['CHEAPERGEN_API_KEY']}"}

# 1. Submit the job
job = requests.post(f"{API}/run/bfl/flux-2-klein-4b/text-to-image", headers=headers, json={
    "prompt": "A cozy coffee shop interior with vintage furniture, morning light, photo",
    "aspect_ratio": "1:1",
    "resolution": "1K"
}).json()

# 2. Poll until it finishes (or pass "webhook_url" and skip polling)
while job["status"] in ("queued", "running"):
    time.sleep(3)
    job = requests.get(f"{API}/generations/{job['id']}", headers=headers).json()

print(job["status"], job["output"]["images"][0]["url"] if job["status"] == "succeeded" else job["error"])

const API = "https://cheapergen.com/api/v1";
const headers = {
  Authorization: `Bearer ${process.env.CHEAPERGEN_API_KEY}`,
  "Content-Type": "application/json",
};

// 1. Submit the job
let job = await fetch(`${API}/run/bfl/flux-2-klein-4b/text-to-image`, {
  method: "POST",
  headers,
  body: JSON.stringify({
    "prompt": "A cozy coffee shop interior with vintage furniture, morning light, photo",
    "aspect_ratio": "1:1",
    "resolution": "1K"
  }),
}).then((r) => r.json());

// 2. Poll until it finishes (or pass webhook_url and skip polling)
while (job.status === "queued" || job.status === "running") {
  await new Promise((r) => setTimeout(r, 3000));
  job = await fetch(`${API}/generations/${job.id}`, { headers }).then((r) => r.json());
}

console.log(job.status === "succeeded" ? job.output.images[0].url : job.error);

curl -X POST https://cheapergen.com/api/v1/run/bfl/flux-2-klein-4b/text-to-image \
  -H "Authorization: Bearer $CHEAPERGEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "prompt": "A cozy coffee shop interior with vintage furniture, morning light, photo",
  "aspect_ratio": "1:1",
  "resolution": "1K"
}'

Text to Image

bfl/flux-2-klein-4b/text-to-image

Image Edit

bfl/flux-2-klein-4b/edit

Example prompts

Hit “Try it” to load a prompt into the playground above.

Flat-lay of breakfast on a marble table, top-down, bright daylight
Try it
Image Edit
Make the jacket in image 1 bright yellow, keep everything else
Try it

FLUX.2 [klein] 4B FAQ

Per image by output size (megapixels) — a fraction of a cent at 1K. Failed generations are not charged.

Yes. FLUX.2 [klein] 4B is BFL's open-weights (Apache-2.0) model, served on an optimized inference engine for open-source models.

Yes — the 4B weights are Apache-2.0 — subject to our Terms of Service.

Related models

Black Forest Labs

PopularUp to −36%

FLUX.2[pro]

Text → Image · Image Edit

from$0.026/img$0.03

Black Forest Labs' production image model — photoreal, fast, up to 4 MP

Krea

Best valueUp to −63%

Krea 2Turbo

Text → Image

from$0.0055/img$0.015

Krea's photographic image model in 8 steps — under a cent an image

Alibaba

Best valueUp to −89%

Z-ImageTurbo