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.
Total Context | Max Output | Input Price | Output Price | Cache Read | Cache Write | Input Audio | Input Audio Cache |
|---|---|---|---|---|---|---|---|
2M | 30K | ≤128K$0.20>128K$0.40 | ≤128K$0.50>128K$1 | ≤128K$0.05>128K$0.05 | -- | -- | -- |
When an error occurs in an upstream provider, we can recover by routing to another healthy provider, if your request filters allow it.
Learn more about our load balancing and customization options.
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.
from openai import OpenAI
client = OpenAI(
base_url="https://openrouter.ai/api/v1",
api_key="<OPENROUTER_API_KEY>",
)
completion = client.chat.completions.create(
extra_headers={
"HTTP-Referer": "<YOUR_SITE_URL>", # Optional. Site URL for rankings on openrouter.ai.
"X-Title": "<YOUR_SITE_NAME>", # Optional. Site title for rankings on openrouter.ai.
},
extra_body={},
model="x-ai/grok-4-fast",
messages=[
{
"role": "user",
"content": [
{
"type": "text",
"text": "What is in this image?"
},
{
"type": "image_url",
"image_url": {
"url": "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Gfp-wisconsin-madison-the-nature-boardwalk.jpg/2560px-Gfp-wisconsin-madison-the-nature-boardwalk.jpg"
}
}
]
}
]
)
print(completion.choices[0].message.content)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.