Model Comparison
Grok-4 Heavy vs Llama 3.1 405B InstructWhich is better in 2026?
Grok-4 Heavy significantly outperforms across most benchmarks.
Verdict: Grok-4 Heavy vs Llama 3.1 405B Instruct — which is better?
Grok-4 Heavy (by xAI) and Llama 3.1 405B Instruct (by Meta) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.
Grok-4 Heavy outperforms in 1 benchmarks (GPQA), while Llama 3.1 405B Instruct is better at 0 benchmarks. Grok-4 Heavy significantly outperforms across most benchmarks.
Choose Grok-4 Heavy if…
- you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
Choose Llama 3.1 405B Instruct if…
- you need open weights you can self-host or fine-tune
Performance Benchmarks
Comparative analysis across standard metrics
Grok-4 Heavy outperforms in 1 benchmarks (GPQA), while Llama 3.1 405B Instruct is better at 0 benchmarks.
Grok-4 Heavy significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Context Window
Maximum input and output token capacity
Only Llama 3.1 405B Instruct specifies input context (128,000 tokens). Only Llama 3.1 405B Instruct specifies output context (128,000 tokens).
Input Capabilities
Supported data types and modalities
Grok-4 Heavy supports multimodal inputs, whereas Llama 3.1 405B Instruct does not.
Grok-4 Heavy can handle both text and other forms of data like images, making it suitable for multimodal applications.
Grok-4 Heavy
Llama 3.1 405B Instruct
License
Usage and distribution terms
Grok-4 Heavy is licensed under a proprietary license, while Llama 3.1 405B Instruct uses Llama 3.1 Community License.
License differences may affect how you can use these models in commercial or open-source projects.
Proprietary
Closed source
Llama 3.1 Community License
Open weights
Release Timeline
When each model was launched
Llama 3.1 405B Instruct was released on 2024-07-23, while Grok-4 Heavy's release date is not specified.
We can confirm Llama 3.1 405B Instruct's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.
—
Jul 23, 2024
2.0 years ago
Knowledge Cutoff
When training data ends
Grok-4 Heavy has a documented knowledge cutoff of 2024-12-31, while Llama 3.1 405B Instruct'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 Llama 3.1 405B Instruct's cutoff date.
Dec 2024
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Outputs Comparison
Key Takeaways
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against Grok-4 Heavy and Llama 3.1 405B Instruct side-by-side, then vote on the output you prefer.
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FAQ
Common questions about Grok-4 Heavy vs Llama 3.1 405B Instruct.