Released Sep 19, 2025Knowledge cutoff Sep 30, 20252,000,000 context
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.
Reasoning can be enabled/disabled using the reasoningenabled parameter in the API. Learn more in our docs
Recent activity on Grok 4 Fast
Total usage per day on OpenRouter
Prompt
4.84B
Reasoning
815M
Completion
616M
Prompt tokens measure input size. Reasoning tokens show internal thinking before a response. Completion tokens reflect total output length.