Model Comparison
GPT-5.1 Instant vs Grok-4 HeavyWhich is better in 2026?
Grok-4 Heavy significantly outperforms across most benchmarks.
Verdict: GPT-5.1 Instant vs Grok-4 Heavy — which is better?
GPT-5.1 Instant (by OpenAI) and Grok-4 Heavy (by xAI) 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.
GPT-5.1 Instant outperforms in 0 benchmarks, while Grok-4 Heavy is better at 2 benchmarks (AIME 2025, GPQA). Grok-4 Heavy significantly outperforms across most benchmarks.
Choose GPT-5.1 Instant if…
- you want predictable pricing at $1.25/M input and $10.00/M output
Choose Grok-4 Heavy if…
- you want the strongest raw capability — it leads on 2 of 2 shared benchmarks
Performance Benchmarks
Comparative analysis across standard metrics
GPT-5.1 Instant outperforms in 0 benchmarks, while Grok-4 Heavy is better at 2 benchmarks (AIME 2025, GPQA).
Grok-4 Heavy significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Context Window
Maximum input and output token capacity
Only GPT-5.1 Instant specifies input context (400,000 tokens). Only GPT-5.1 Instant specifies output context (128,000 tokens).
Input Capabilities
Supported data types and modalities
Both GPT-5.1 Instant and Grok-4 Heavy support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GPT-5.1 Instant
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
GPT-5.1 Instant was released on 2025-11-12, while Grok-4 Heavy's release date is not specified.
We can confirm GPT-5.1 Instant's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.
Nov 12, 2025
8 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 GPT-5.1 Instant'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 GPT-5.1 Instant's cutoff date.
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Dec 2024
Outputs Comparison
Key Takeaways
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against GPT-5.1 Instant and Grok-4 Heavy side-by-side, then vote on the output you prefer.
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FAQ
Common questions about GPT-5.1 Instant vs Grok-4 Heavy.