xAI: Grok 4 Fast
OpenAI • text • vision • function-calling • json-mode
Provider ID
x-ai/grok-4-fastGrok 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 using the `reasoning` `enabled` parameter in the API. [Learn more in our docs](https://openrouter.ai/docs/use-cases/reasoning-tokens#controlling-reasoning-tokens)
Quick Summary
Best For:
High-volume, low-latency tasks where cost efficiency is paramount
Pricing:
$0.00/1M input tokens, $0.00/1M output tokens
Context Window:
2,000,000 tokens (Large - suitable for extensive codebases)
Key Differentiator:
Cost-optimized for high-volume usage
Specifications
Context Window
2,000,000 tokens
Max Output Tokens
30,000 tokens
Streaming
Yes
JSON Mode
Yes
Vision
Yes
Tier
Affordable
Capabilities
text
vision
function-calling
json-mode
Tags