Model Comparison
Grok-4.1 Fast Reasoning vs Grok-4 Heavy
Comparing Grok-4.1 Fast Reasoning and Grok-4 Heavy across benchmarks, pricing, and capabilities.
Performance Benchmarks
Comparative analysis across standard metrics
Grok-4.1 Fast Reasoning and Grok-4 Heavy don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Arena Performance
Human preference votes
Context Window
Maximum input and output token capacity
Only Grok-4.1 Fast Reasoning specifies input context (2,000,000 tokens). Only Grok-4.1 Fast Reasoning specifies output context (30,000 tokens).
Input Capabilities
Supported data types and modalities
Both Grok-4.1 Fast Reasoning and Grok-4 Heavy support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Grok-4.1 Fast Reasoning
Grok-4 Heavy
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Grok-4.1 Fast Reasoning was released on 2025-11-17, while Grok-4 Heavy's release date is not specified.
We can confirm Grok-4.1 Fast Reasoning's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.
Nov 17, 2025
6 months ago
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Knowledge Cutoff
When training data ends
Grok-4 Heavy has a documented knowledge cutoff of 2024-12-31, while Grok-4.1 Fast Reasoning's cutoff date is not specified.
We can confirm Grok-4 Heavy's training data extends to 2024-12-31, but cannot make a direct comparison without Grok-4.1 Fast Reasoning's cutoff date.
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Dec 2024
Outputs Comparison
Key Takeaways
No standout differentiators in the data we have for this pair.
Detailed Comparison
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FAQ
Common questions about Grok-4.1 Fast Reasoning vs Grok-4 Heavy.