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Black Forest Labs: FLUX.2 Klein 4B

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. Priced at $0.014 per megapixel. 40,960 token context window. Includes independent benchmarks from Artificial Analysis.

View source on OpenRouter Hugging Face
Overview

Model specifications

Context
40,960 tokens
Maximum output
36,864 tokens
Architecture
text+image->image
Tokenizer
Other
Knowledge cutoff
Not provided
Moderated
No
OPENROUTER

Complete pricing

Synchronized OpenRouter rates. Token prices are shown per one million tokens.

Image
$0.014
/megapixel
API

Quick start

Call this exact model ID through OpenRouter’s OpenAI-compatible API.

curl https://openrouter.ai/api/v1/chat/completions \
  -H "Authorization: Bearer $OPENROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"black-forest-labs/flux.2-klein-4b","messages":[{"role":"user","content":"Hello!"}]}'
Capabilities

Input → Output

Input
textimage
Output
image
API

Supported API parameters

seed
Available providers

1 Provider

Live providers on OpenRouter

Provider availability, latency, throughput and routing can change continuously. Open the source page for current operational data.

OpenRouter

Black Forest Labs

unknown
Context
41K
Maximum output
37K
Input
Free
Output
Free
Cache read
Not provided
Cache write
Not provided
black-forest-labs

models

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Black Forest Labs: FLUX Video Upscale

FLUX Video Upscale is a video upscaling model from Black Forest Labs. It enlarges a single source video by 1.5× to 3× while preserving its duration, with an optional prompt...

Context
Not provided
Input
text · video
Output
video
Input: FreeOutput: Freeper 1M tokens
View model details →
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Black Forest Labs: FLUX.3 Video

FLUX.3 Video is a video generation model from Black Forest Labs. It supports text-to-video, image-guided generation with opening and closing keyframes, and video continuation workflows, making it suited for controlled...

Context
Not provided
Input
text · image · video
Output
video
Input: FreeOutput: Freeper 1M tokens
View model details →
black-forest-labs logoblack-forest-labs

Black Forest Labs: FLUX.2 Max

FLUX.2 [max] is the new top-tier image model from Black Forest Labs, pushing image quality, prompt understanding, and editing consistency to the highest level yet. Pricing is as follows, [per...

Context
47K
Input
text · image
Output
image
Input: FreeOutput: Freeper 1M tokens
View model details →
black-forest-labs logoblack-forest-labs

Black Forest Labs: FLUX.2 Flex

FLUX.2 [flex] excels at rendering complex text, typography, and fine details, and supports multi-reference editing in the same unified architecture. Pricing is as follows, per the docs: We charge $0.06...

Context
67K
Input
text · image
Output
image
Input: FreeOutput: Freeper 1M tokens
View model details →