FLUX.2 Klein 4B API

blackforestlabs/flux-2-klein-4b
Compact 4B FLUX.
Output
$0.0182 / MP (variable)
Released
Jun 12, 2026

How to use FLUX.2 Klein 4B API

Install any OpenAI-compatible SDK, point it at api.aimlapi.com/v1, and set the model to blackforestlabs/flux-2-klein-4b.
import requests

r = requests.post(
    "https://api.aimlapi.com/v1/images/generations",
    headers={"Authorization": "Bearer " + AIMLAPI_KEY},
    json={
      "model": "blackforestlabs/flux-2-klein-4b",
      "prompt": "A cat holding a sign that says hello"
    },
)
print(r.json())
const r = await fetch("https://api.aimlapi.com/v1/images/generations", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "blackforestlabs/flux-2-klein-4b",
    "prompt": "A cat holding a sign that says hello"
  }),
});
console.log(await r.json());
curl -X POST https://api.aimlapi.com/v1/images/generations \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"blackforestlabs/flux-2-klein-4b","prompt":"A cat holding a sign that says hello"}'

OpenAI-compatible — swap the base URL and it works with your existing SDK.

FLUX.2 Klein 4B API Pricing

TypePrice
Output
$0.0182 / MP (variable)

FLUX.2 Klein 4B Benchmarks

BenchmarkScoreWhat it measuresSourceRetrieved
Text-to-Image Arena
864
Human preference Elo from blind pairwise comparisons of generated images, measured independently by Artificial AnalysisSourceSeptember 28, 2026

FLUX.2 Klein 4B vs other models

ModelInputOutputContextBest for
$0.0182 / MP (variable)
Image generation at scale
$0.325 / 1M tokens
$78 / 1M tokens
128K tokens
Image generation at scale
$6.5 / 1M tokens
$39 / 1M tokens
Image generation at scale
Image generation at scale
$0.0195 / MP (variable)
Image generation at scale

Frequently asked questions

FLUX.2 Klein 4B takes image, text as input and returns image.

FLUX.2 Klein 4B became available on June 12, 2026.

FLUX.2 Klein 4B is priced at $0.0182 / MP (variable).

FLUX.2 Klein 4B is billed per generation — a fixed charge per output rather than by prompt length.

Yes, FLUX.2 Klein 4B accepts image input as well as a text prompt.

FLUX.2 Klein 4B was built by Black Forest Labs.

Send a request to https://api.aimlapi.com/v1/images/generations with blackforestlabs/flux-2-klein-4b as the model id.

Yes. FLUX.2 Klein 4B is served through AI/ML API, so the same key and endpoint format used for other models applies.

FLUX.2 Klein 4B is a 4 billion parameter model, as indicated by its name.

It is a compact 4B version of FLUX.2 built for efficient image generation.

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