Model Comparison

Claude Opus 5 vs Grok-4 HeavyWhich is better in 2026?

Claude Opus 5 significantly outperforms across most benchmarks.

Verdict: Claude Opus 5 vs Grok-4 Heavy — which is better?

Claude Opus 5 (by Anthropic) 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.

Claude Opus 5 outperforms in 1 benchmarks (Humanity's Last Exam), while Grok-4 Heavy is better at 0 benchmarks. Claude Opus 5 significantly outperforms across most benchmarks.

Choose Claude Opus 5 if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks

Choose Grok-4 Heavy if…

  • you are already invested in the xAI ecosystem

Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

Claude Opus 5 outperforms in 1 benchmarks (Humanity's Last Exam), while Grok-4 Heavy is better at 0 benchmarks.

Claude Opus 5 significantly outperforms across most benchmarks.

Sun Jul 26 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Claude Opus 5 specifies input context (1,000,000 tokens). Only Claude Opus 5 specifies output context (128,000 tokens).

Anthropic
Claude Opus 5
Input1,000,000 tokens
Output128,000 tokens
xAI
Grok-4 Heavy
Input- tokens
Output- tokens
Sun Jul 26 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Claude Opus 5 and Grok-4 Heavy support multimodal inputs.

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

Claude Opus 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.

Claude Opus 5

Proprietary

Closed source

Grok-4 Heavy

Proprietary

Closed source

Release Timeline

When each model was launched

Claude Opus 5 was released on 2026-07-24, while Grok-4 Heavy's release date is not specified.

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

Claude Opus 5

Jul 24, 2026

1 days ago

Grok-4 Heavy

—

Knowledge Cutoff

When training data ends

Grok-4 Heavy has a documented knowledge cutoff of 2024-12-31, while Claude Opus 5'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 Claude Opus 5's cutoff date.

Claude Opus 5

—

Grok-4 Heavy

Dec 2024

Outputs Comparison

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Key Takeaways

Anthropic
Larger context window (1,000,000 tokens)
Higher Humanity's Last Exam score (64.7% vs 50.7%)
xAI

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

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Claude Opus 5 and Grok-4 Heavy side-by-side, then vote on the output you prefer.

Claude Opus 5
✓ Preferred
Grok-4 Heavy
Open in Playground
AI Model Comparison Table
Feature
Anthropic
Claude Opus 5
xAI
Grok-4 Heavy

FAQ

Common questions about Claude Opus 5 vs Grok-4 Heavy.

Which is better, Claude Opus 5 or Grok-4 Heavy?

Claude Opus 5 significantly outperforms across most benchmarks. Claude Opus 5 is made by Anthropic 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 Claude Opus 5 compare to Grok-4 Heavy in benchmarks?

Claude Opus 5 scores BrowseComp: 90.8%, BioMysteryBench: 90.1%, OSWorld 2.0: 70.6%, DeepSWE 1.1: 68.8%, Humanity's Last Exam: 64.7%. 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 Claude Opus 5 and Grok-4 Heavy?

Claude Opus 5 supports 1.0M 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 Claude Opus 5 and Grok-4 Heavy?

Claude Opus 5 is developed by Anthropic and Grok-4 Heavy is developed by xAI.

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