YepAPI
Black Forest LabsImage Generation/v1/media/queue

FLUX.2 Klein API

FLUX.2 Klein from $0.03 per image — the compact 4B FLUX model for high-volume generation.

The compact 4B FLUX.2 model. Fast, cheap image generation from $0.03 with the full FLUX.2 aspect-ratio range and reference-image editing.

No credit card required. Takes 30 seconds.

FLUX.2 Klein API pricing

Pay per request from your YepAPI balance — no subscription, no monthly minimum. Prices updated October 23, 2026.

BillingPrice
Rate$0.03/image
What it costsPer job
1 imagefrom default size$0.03
100 imagesa product catalog batch$3.00
1,000 imagesa month of app traffic$30.00

2,400+

Developers

1.2M+

API calls served

100+

Endpoints

$0.01

Per call

Yep, that's it.

Try it live

Enter a prompt and generate an image with FLUX.2 Klein.

POST/v1/media/queue

Drop image or click to upload

For image-to-image editing

Response
Hit "Send Request" to see the response

FLUX.2 Klein specs

ProviderBlack Forest Labs
Model IDblack-forest-labs/flux.2-klein-4b
Endpoint/v1/media/queue
TypeImage Generation
Aspect ratios1:1, 4:3, 3:4, 3:2, 2:3, 16:9, 9:16, 21:9, auto
Output formatspng, jpeg
Image inputYes

How to get a FLUX.2 Klein API key

  1. 1

    Create a free account

    Sign up at yepapi.com with Google or email. It takes about 30 seconds and needs no card.

  2. 2

    Create an API key

    Open the dashboard, go to API Keys and create a key. Copy it — it starts with yep_sk_.

  3. 3

    Call FLUX.2 Klein

    Send a request to /v1/media/queue with the x-api-key header and model "black-forest-labs/flux.2-klein-4b".

  4. 4

    Pay as you go

    Usage is billed per request from your balance. Top up any amount; there is no subscription.

Strengths

✓
Cheapest FLUX tier

At around $0.03 per image, Klein makes large batches, thumbnails, and prompt exploration affordable at volume.

✓
Fast turnaround

The compact 4B architecture renders quickly, keeping iteration loops tight when you are still hunting for the right prompt.

✓
Full aspect-ratio range

Supports the same nine aspect ratios as the larger FLUX.2 tiers, so drafts frame identically to finals.

✓
Draft-then-promote

Explore on Klein, then re-run the winning prompts on FLUX.2 Pro or Max — same family, same endpoint, one key.

Quick start

Copy this snippet and start making calls with FLUX.2 Klein.

// Step 1: Submit job
const res = await fetch('https://api.yepapi.com/v1/media/queue', {
  method: 'POST',
  headers: {
    'x-api-key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "model": "black-forest-labs/flux.2-klein-4b",
    "prompt": "Flat-lay of hiking gear on pale birch — enamel mug, folded topo map, worn leather boots, brass compass, soft overcast daylight, muted forest palette",
    "options": {
      "aspectRatio": "1:1"
    }
  }),
});
const { data } = await res.json();
const jobId = data.jobId;

// Step 2: Poll for result
const status = await fetch(`https://api.yepapi.com/v1/media/status/${jobId}`, {
  headers: { 'x-api-key': 'YOUR_API_KEY' },
});
const { data: job } = await status.json();
// job.status: "pending" | "processing" | "completed" | "failed"
// job.result: { text?, image?, audio?, video? }

FLUX.2 Klein vs similar models

Every model below runs on the same API key — switch by changing the model ID.

ModelProviderPrice
FLUX.2 KleinBlack Forest Labsfrom $0.03/image
FLUX 3 Image KleinBlack Forest Labsfrom $0.02/image
FLUX.2 ProBlack Forest Labsfrom $0.07/image
FLUX.2 FlexBlack Forest Labsfrom $0.11/image
FLUX 3 ImageBlack Forest Labsfrom $0.11/image
FLUX.2 MaxBlack Forest Labsfrom $0.15/image
GPT Image 2OpenAIfrom $0.02/image
GPT Image 1 MiniOpenAIfrom $0.02/image

Why use FLUX.2 Klein through YepAPI?

✓One API key for all models — no separate accounts
✓No monthly minimums — pay per call
✓Switch models with one line of code
✓Simple REST API — works from any language
✓Unified billing across all providers
✓No rate limits for most use cases

FLUX.2 Klein API — compact 4B image generation from $0.03

FLUX.2 Klein is the small, fast member of the FLUX.2 family — a 4-billion-parameter model built for volume. It keeps the FLUX aspect-ratio range and reference-image editing while cutting cost and render time dramatically.

On YepAPI, Klein costs about $0.03 per image on the shared `/v1/media/queue` endpoint, which makes it the natural first pass for prompt exploration, A/B creative, and batch thumbnail generation.

Start generating in 30 seconds

$5 free credit on signup. No credit card required. Pay per call.

What developers say

“Switched from SerpAPI and cut our SERP costs by 80%. Same data quality, way simpler billing.”

Marcus T.

SEO Platform Founder

“One API key for AI models, SERP data, and web scraping. Saved us from managing 4 separate providers.”

Priya S.

Full-Stack Developer

“The $5 free credit let us prototype our entire rank tracking feature before committing. No other API does that.”

Jake R.

Indie Hacker

Frequently asked questions

The compact 4B FLUX.2 model. Fast, cheap image generation from $0.03 with the full FLUX.2 aspect-ratio range and reference-image editing.

FLUX.2 Klein costs from $0.03/image through YepAPI, billed per request with no monthly fee. For example, a 1 image (from default size) costs about $0.03.

Sign up at yepapi.com (Google or email, about 30 seconds), open the dashboard and create an API key. The same key works for FLUX.2 Klein and every other model — no separate Black Forest Labs account or waitlist.

New YepAPI accounts in most countries get free signup credit, enough to test FLUX.2 Klein without a card. After that you pay per request at the rates above — there is no subscription.

Use "black-forest-labs/flux.2-klein-4b" as the model on /v1/media/queue. The short alias "flux-klein" also works.

Ready to use FLUX.2 Klein?

$5 free credit on signup. No credit card required. Pay per call.

Explore more models