Model Comparison

GPT-5 vs Grok-4 Heavy

Grok-4 Heavy significantly outperforms across most benchmarks.

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Performance Benchmarks

Comparative analysis across standard metrics

3 benchmarks

GPT-5 outperforms in 0 benchmarks, while Grok-4 Heavy is better at 3 benchmarks (AIME 2025, GPQA, Humanity's Last Exam).

Grok-4 Heavy significantly outperforms across most benchmarks.

Sun May 10 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only GPT-5 specifies input context (400,000 tokens). Only GPT-5 specifies output context (128,000 tokens).

OpenAI
GPT-5
Input400,000 tokens
Output128,000 tokens
xAI
Grok-4 Heavy
Input- tokens
Output- tokens
Sun May 10 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5 and Grok-4 Heavy support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

GPT-5

Text
Images
Audio
Video

Grok-4 Heavy

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

GPT-5

Proprietary

Closed source

Grok-4 Heavy

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5 was released on 2025-08-07, while Grok-4 Heavy's release date is not specified.

We can confirm GPT-5's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

GPT-5

Aug 7, 2025

9 months ago

Grok-4 Heavy

—

Knowledge Cutoff

When training data ends

GPT-5 has a knowledge cutoff of 2024-09-30, while Grok-4 Heavy has a cutoff of 2024-12-31.

Grok-4 Heavy has more recent training data (up to 2024-12-31), making it potentially better informed about events through that date compared to GPT-5 (2024-09-30).

GPT-5

Sep 2024

Grok-4 Heavy

Dec 2024

3 mo newer

Outputs Comparison

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Key Takeaways

OpenAI
Larger context window (400,000 tokens)
xAI
Higher AIME 2025 score (100.0% vs 94.6%)
Higher GPQA score (88.4% vs 85.7%)
Higher Humanity's Last Exam score (50.7% vs 24.8%)

Detailed Comparison

AI Model Comparison Table
Feature
OpenAI
GPT-5
xAI
Grok-4 Heavy

FAQ

Common questions about GPT-5 vs Grok-4 Heavy.

Which is better, GPT-5 or Grok-4 Heavy?

Grok-4 Heavy significantly outperforms across most benchmarks. GPT-5 is made by OpenAI and Grok-4 Heavy is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5 compare to Grok-4 Heavy in benchmarks?

GPT-5 scores SWE-Lancer (IC-Diamond subset): 100.0%, COLLIE: 99.0%, Tau2 Telecom: 96.7%, OpenAI-MRCR: 2 needle 128k: 95.2%, AIME 2025: 94.6%. Grok-4 Heavy scores AIME 2025: 100.0%, HMMT25: 96.7%, GPQA: 88.4%, LiveCodeBench: 79.4%, USAMO25: 61.9%.

What are the context window sizes for GPT-5 and Grok-4 Heavy?

GPT-5 supports 400K tokens and Grok-4 Heavy supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

Who makes GPT-5 and Grok-4 Heavy?

GPT-5 is developed by OpenAI and Grok-4 Heavy is developed by xAI.