Black Forest LabsimageFastOperational

FLUX.2 [klein] 4B Text to Image API

Name: FLUX.2 [klein] 4B API
Brand: Black Forest Labs
SKU: bfl/flux-2-klein-4b
Availability: InStock

Text to Image with FLUX.2 [klein] 4B by Black Forest Labs. The fastest FLUX.2 — open weights, sub-second, a fraction of a cent.

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

FromUp to −95%

$0.0007/img$0.014

per image · 1K

Open in Studio API

Try FLUX.2 [klein] 4B Text to Image

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.

Also available: FLUX.2 [klein] 4B Image Edit

FLUX.2 [klein] 4B Text to Image API

POST/api/v1/run/bfl/flux-2-klein-4b/text-to-image

Submits an asynchronous job and returns 202 with a generation id. Poll GET /api/v1/generations/{id} or pass webhook_url. See job lifecycle.

Input parameters

Name	Type	Description	Affects price
`prompt`required	string	Describe the shot: subject, action, camera movement, lighting and style.	No
`aspect_ratio`	string (enum)	Output image shape. Values: 1:1 · 4:3 · 3:4 · 16:9 · 9:16 · 3:2 · 2:3 Default: 1:1	Yes
`resolution`	string (enum)	1K ≈ 1 MP; 2K ≈ 4 MP (long side up to 2048 px). Values: 1K · 2K Default: 1K	Yes
`seed`	integer	Use the same seed and settings to reproduce a result. Leave empty for random.	No
`webhook_url`	string (URL)	Optional. We POST the finished generation here, signed with your webhook secret. Webhooks	No

Request

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"
}'

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);

Response

{
  "id": "gen_8c2QmX1nq0k4",
  "object": "generation",
  "model": "bfl/flux-2-klein-4b",
  "endpoint": "bfl/flux-2-klein-4b/text-to-image",
  "mode": "text-to-image",
  "status": "queued",
  "input": {
    "prompt": "A cozy coffee shop interior with vintage furniture, morning light, photo",
    "aspect_ratio": "1:1",
    "resolution": "1K"
  },
  "output": null,
  "error": null,
  "cost": {
    "amount_usd": 0.2255,
    "currency": "usd",
    "estimated": true,
    "official_usd": null,
    "saved_usd": null
  },
  "source": "api",
  "started_at": null,
  "completed_at": null,
  "urls": {
    "get": "https://cheapergen.com/api/v1/generations/gen_8c2QmX1nq0k4",
    "cancel": "https://cheapergen.com/api/v1/generations/gen_8c2QmX1nq0k4/cancel"
  },
  "created_at": "2026-10-15T09:21:04Z"
}

{
  "id": "gen_8c2QmX1nq0k4",
  "object": "generation",
  "model": "bfl/flux-2-klein-4b",
  "endpoint": "bfl/flux-2-klein-4b/text-to-image",
  "mode": "text-to-image",
  "status": "succeeded",
  "input": {
    "prompt": "A cozy coffee shop interior with vintage furniture, morning light, photo",
    "aspect_ratio": "1:1",
    "resolution": "1K"
  },
  "output": {
    "images": [
      {
        "url": "https://cdn.cheapergen.ai/outputs/gen_8c2Q-0.png",
        "content_type": "image/png",
        "width": 2048,
        "height": 2048
      }
    ]
  },
  "error": null,
  "cost": {
    "amount_usd": 0.2255,
    "currency": "usd",
    "estimated": false,
    "official_usd": 0.264,
    "saved_usd": 0.0385
  },
  "source": "api",
  "created_at": "2026-10-15T09:21:04Z",
  "started_at": "2026-10-15T09:21:06Z",
  "completed_at": "2026-10-15T09:22:31Z"
}

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.

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