FLUX 3 Klein API: Kie AI's image-generation model, one key away
FLUX 3 Klein via the ApexApi gateway
FLUX 3 Klein is the small, low-cost model of Black Forest Labs' FLUX 3 family. It renders a prompt at 1K, 2K or 4K in 1:1, 16:9, 9:16, 3:4 or 4:3. Choose it over FLUX.2 for high-volume work where price per image matters most. Call it through ApexApi's unified, OpenAI-compatible API with one `ak-` key, alongside every other model in the catalog. Pricing is $0.010–$0.039/image per image, billed pay-per-use from your credit balance with no subscription.
FLUX 3 Klein is served through ApexApi's unified, OpenAI-compatible API. One key, one format, with smart routing and automatic failover. Provider: Kie AI.
Why FLUX 3 Klein
Text-to-image generation
High-quality image generation (and image-to-image where supported) through one API.
Transparent pricing ($0.010–$0.039/image)
Pay per image from your credit balance. Failed generations aren't billed.
OpenAI-compatible
Drop-in with any OpenAI SDK. Change the base URL and key, keep your code.
Specifications
- Modality
- image
- Context window
- —
- Max output
- —
- Streaming
- —
- Tool / function calling
- —
- Vision input
- —
FLUX 3 Klein pricing
- That makes it the 3rd cheapest of the 33 image models we serve, ranked on output price.
- It runs 6.3× cheaper than FLUX.1 Pro, the pricier option from the same maker.
Getting started with FLUX 3 Klein
OpenAI-compatible. Point your client at ApexApi, swap your key, and call it. No new SDK to learn.
import requests
resp = requests.post(
"https://api.apexapi.dev/v1/images/generations",
headers={"Authorization": "Bearer <YOUR_APEXAPI_KEY>"},
json={"model": "black-forest-labs/flux-3-klein", "prompt": "A serene mountain lake at golden hour"},
)
print(resp.json())FLUX 3 Klein use cases
What teams build with FLUX 3 Klein on ApexApi.
Marketing & creative
On-brand visuals, ad creative, and product imagery at scale.
In-product generation
Generate images inside your app from user prompts.
Prototyping
Rapid concept art and design exploration.
FLUX 3 Klein vs other models
How it compares, and on ApexApi you can switch between any of them with a single string change, same key, same endpoint.
FLUX 3 Klein vs Nano Banana Pro
Compare FLUX 3 Klein against this model on price, capabilities, and latency. A/B them with a single key on ApexApi.
Learn more about Nano Banana Pro API →FLUX 3 Klein vs FLUX.2 Pro
Compare FLUX 3 Klein against this model on price, capabilities, and latency. A/B them with a single key on ApexApi.
Learn more about FLUX.2 Pro API →FLUX 3 Klein API: FAQ
How do I call FLUX 3 Klein through ApexApi?
Create an ApexApi key, point your client at https://api.apexapi.dev/v1, and POST to /v1/images/generations with the model set to `black-forest-labs/flux-3-klein`. The API is OpenAI-compatible, so an existing OpenAI SDK works once you change the base URL and key.
How much does FLUX 3 Klein cost on ApexApi?
$0.010–$0.039/image, billed per image with no subscription or minimum. The exact figure is shown before you generate, so nothing is charged against a price you have not seen.
What should I use instead of FLUX 3 Klein?
From the same maker, FLUX.1 Schnell costs less for lighter work and FLUX.2 is the step up when this one falls short. Switching is one string: both run on the same endpoint and the same key, so there is nothing to re-integrate.
Ready to build with FLUX 3 Klein?
One API key. Every major AI model. Pay only for what you use.
Try FLUX 3 Klein, pay as you go from $5