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Black Forest Labs: FLUX.2 Klein 4B

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

Created Jan 14, 202667,344 context
$0.24/M input tokens$0.24/M output 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.

Sample code and API for FLUX.2 Klein 4B

OpenRouter normalizes requests and responses across providers for you.

OpenRouter supports image generation through models that have image in their output modalities. These models can create images from text prompts when you specify modalities: ["image", "text"] 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.