xAI: Grok 4 Fast
Grok 4 Fast is xAI's latest multimodal model with SOTA cost-efficiency and a 2M token context window. It comes in two flavors: non-reasoning and reasoning. Read more about the model on xAI's [news post](http://x.ai/news/grok-4-fast). Reasoning can be enabled/disabled using the `reasoning` `enabled` parameter in the API. [Learn more in our docs](https://openrouter.ai/docs/use-cases/reasoning-tokens#controlling-reasoning-tokens)
Undisclosed
Parameters
2.0M tokens
Context Window
Proprietary
License
Sep 19, 2025
Released
💰 Pricing
Input
$0.20
per 1M tokens
Output
$0.50
per 1M tokens
API Available
This model is accessible via API for integration into your applications.
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