Black Forest Labs: FLUX.2 Klein 4B

black-forest-labs/flux.2-klein-4b

Released Jan 14, 202640,960 context

$0/M input tokens$0/M output tokens$3.418/M tokens

FLUX.2 [klein] 4B is the fastest and most cost-effective model in the FLUX.2 family, optimized for high-throughput use cases while maintaining excellent image quality.

Pricing is based on the output image. The first generated megapixel is charged $0.014. Each subsequent megapixel is charged $0.001.

Providers for FLUX.2 Klein 4B

OpenRouter routes requests to the best providers that are able to handle your prompt size and parameters, with fallbacks to maximize uptime.

Performance for FLUX.2 Klein 4B

Compare different providers across OpenRouter

Effective Pricing for FLUX.2 Klein 4B

Actual cost per million tokens across providers over the past hour

Apps using FLUX.2 Klein 4B

Top public apps this month

Recent activity on FLUX.2 Klein 4B

Total usage per day on OpenRouter

Prompt

Completion

Prompt tokens measure input size. Reasoning tokens show internal thinking before a response. Completion tokens reflect total output length.

Uptime stats for FLUX.2 Klein 4B

Uptime stats for FLUX.2 Klein 4B across all providers

Sample code and API for FLUX.2 Klein 4B

OpenRouter normalizes requests and responses across providers for you.

OpenRouter supports image generation models that only output images and not text. These models can create images from text prompts when you specify modalities: ["image"] in your request. The generated images are returned as base64-encoded data URLs in the assistant message. Learn more about image generation.

In the examples below, the OpenRouter-specific headers are optional. Setting them allows your app to appear on the OpenRouter leaderboards.

Using third-party SDKs

For information about using third-party SDKs and frameworks with OpenRouter, please see our frameworks documentation.

See the Request docs for all possible fields, and Parameters for explanations of specific sampling parameters.

FLUX.2 Klein 4B - API Pricing & Providers | OpenRouter