xAI: Grok 4 Fast

x-ai/grok-4-fast

Created Sep 19, 20252,000,000 context

Starting at $0.20/M input tokensStarting at $0.50/M output tokens

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 using the reasoning enabled parameter in the API. Learn more in our docs

Prompts and completions on Grok 4 Fast Free may be used by xAI or OpenRouter to improve future models.

xAI: Grok 4 Fast

x-ai/grok-4-fast

Created Sep 19, 20252,000,000 context

Starting at $0.20/M input tokensStarting at $0.50/M output tokens

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 using the reasoning enabled parameter in the API. Learn more in our docs

Prompts and completions on Grok 4 Fast Free may be used by xAI or OpenRouter to improve future models.

Sample code and API for Grok 4 Fast

OpenRouter normalizes requests and responses across providers for you.

OpenRouter provides an OpenAI-compatible completion API to 400+ models & providers that you can call directly, or using the OpenAI SDK. Additionally, some third-party SDKs are available.

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.