On September 15, 2025, Elon Musk's xAI company rolled out the Grok 4 Fast model. Users have the option to activate it through the Grok web model selector, which is clearly marked as "Early Access Beta."

The standout feature of Grok 4 Fast is its remarkable speed. Response times are up to 10 times faster compared to the standard Grok 4 model. This is achieved by streamlining the processing time for complex tasks. As a result, it's an ideal choice for users who need immediate answers without any delay.

However, it's worth noting that when faced with creative tasks or assignments that demand fine - grained processing, the model may fall short in terms of content depth and the richness of details. This is a trade - off for its speed advantage.

Previously, Grok 4 Fast was put through internal testing on the Arena platform, where it went by the test name "Sonoma". At present, the model is still in the "Early Access" phase. There's a possibility that it will be made available to free users in the future, and it might even take the place of the older Grok 3 model.

In addition, xAI has introduced an "Update Log" section to the Grok web interface. This allows for real - time public disclosure of the product's iteration progress, keeping users informed about the latest developments. Looking ahead, Grok 4 Fast is set to be adapted for mobile applications, further expanding its accessibility.