Model Comparison

Grok-4 Heavy vs o3-proWhich is better in 2026?

Comparing Grok-4 Heavy and o3-pro across benchmarks, pricing, and capabilities.

Verdict: Grok-4 Heavy vs o3-pro — which is better?

Grok-4 Heavy (by xAI) and o3-pro (by OpenAI) 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.

Choose Grok-4 Heavy if…

  • you are already invested in the xAI ecosystem

Choose o3-pro if…

  • you want predictable pricing at $20.00/M input and $80.00/M output
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Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

Grok-4 Heavy and o3-prodon'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 o3-pro specifies input context (200,000 tokens). Only o3-pro specifies output context (100,000 tokens).

xAI
Grok-4 Heavy
Input- tokens
Output- tokens
OpenAI
o3-pro
Input200,000 tokens
Output100,000 tokens
Tue Jun 16 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Grok-4 Heavy and o3-pro support multimodal inputs.

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

Grok-4 Heavy

Text
Images
Audio
Video

o3-pro

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.

Grok-4 Heavy

Proprietary

Closed source

o3-pro

Proprietary

Closed source

Release Timeline

When each model was launched

o3-pro was released on 2025-06-10, while Grok-4 Heavy's release date is not specified.

We can confirm o3-pro's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

Grok-4 Heavy

—

o3-pro

Jun 10, 2025

1.0 years ago

Knowledge Cutoff

When training data ends

Grok-4 Heavy has a knowledge cutoff of 2024-12-31, while o3-pro has a cutoff of 2024-05-31.

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 o3-pro (2024-05-31).

Grok-4 Heavy

Dec 2024

7 mo newer
o3-pro

May 2024

Outputs Comparison

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Key Takeaways

xAI

No standout differentiators in the data we have for this pair.

OpenAI
Larger context window (200,000 tokens)

Detailed Comparison

AI Model Comparison Table
Feature
xAI
Grok-4 Heavy
OpenAI
o3-pro

FAQ

Common questions about Grok-4 Heavy vs o3-pro.

Which is better, Grok-4 Heavy or o3-pro?

Grok-4 Heavy (xAI) and o3-pro (OpenAI) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does Grok-4 Heavy compare to o3-pro in benchmarks?

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 Grok-4 Heavy and o3-pro?

Grok-4 Heavy supports an unknown number of tokens and o3-pro supports 200K tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

Who makes Grok-4 Heavy and o3-pro?

Grok-4 Heavy is developed by xAI and o3-pro is developed by OpenAI.

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