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Model Comparison

Grok-4 Heavy vs Kimi-k1.5Which is better in 2026?

Comparing Grok-4 Heavy and Kimi-k1.5 across benchmarks, pricing, and capabilities.

Verdict: Grok-4 Heavy vs Kimi-k1.5 — which is better?

Grok-4 Heavy (by xAI) and Kimi-k1.5 (by Moonshot AI) 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 Kimi-k1.5 if…

  • you are already invested in the Moonshot AI ecosystem

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

Grok-4 Heavy and Kimi-k1.5don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Input Capabilities

Supported data types and modalities

Both Grok-4 Heavy and Kimi-k1.5 support multimodal inputs.

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

Grok-4 Heavy

Text
Images
Audio
Video

Kimi-k1.5

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

Kimi-k1.5

Proprietary

Closed source

Release Timeline

When each model was launched

Kimi-k1.5 was released on 2025-01-20, while Grok-4 Heavy's release date is not specified.

We can confirm Kimi-k1.5's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

Grok-4 Heavy

—

Kimi-k1.5

Jan 20, 2025

1.5 years ago

Knowledge Cutoff

When training data ends

Grok-4 Heavy has a documented knowledge cutoff of 2024-12-31, while Kimi-k1.5'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 Kimi-k1.5's cutoff date.

Grok-4 Heavy

Dec 2024

Kimi-k1.5

—

Outputs Comparison

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Key Takeaways

xAI

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

Moonshot AI

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

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Grok-4 Heavy and Kimi-k1.5 side-by-side, then vote on the output you prefer.

Grok-4 Heavy
✓ Preferred
Kimi-k1.5
Open in Playground
AI Model Comparison Table
Feature
xAI
Grok-4 Heavy
Moonshot AI
Kimi-k1.5

FAQ

Common questions about Grok-4 Heavy vs Kimi-k1.5.

Which is better, Grok-4 Heavy or Kimi-k1.5?

Grok-4 Heavy (xAI) and Kimi-k1.5 (Moonshot AI) 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 Kimi-k1.5 in benchmarks?

Grok-4 Heavy scores AIME 2025: 100.0%, HMMT25: 96.7%, GPQA: 88.4%, LiveCodeBench: 79.4%, USAMO25: 61.9%. Kimi-k1.5 scores MATH-500: 96.2%, CLUEWSC: 91.4%, C-Eval: 88.3%, MMLU: 87.4%, IFEval: 87.2%.

Who makes Grok-4 Heavy and Kimi-k1.5?

Grok-4 Heavy is developed by xAI and Kimi-k1.5 is developed by Moonshot AI.

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