Model Comparison

Grok-4 Heavy vs Kimi K3Which is better in 2026?

Kimi K3 significantly outperforms across most benchmarks.

Verdict: Grok-4 Heavy vs Kimi K3 — which is better?

Grok-4 Heavy (by xAI) and Kimi K3 (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.

Grok-4 Heavy outperforms in 0 benchmarks, while Kimi K3 is better at 2 benchmarks (GPQA, Humanity's Last Exam). Kimi K3 significantly outperforms across most benchmarks.

Choose Grok-4 Heavy if…

  • you are already invested in the xAI ecosystem

Choose Kimi K3 if…

  • you want the strongest raw capability — it leads on 2 of 2 shared benchmarks

Performance Benchmarks

Comparative analysis across standard metrics

2 benchmarks

Grok-4 Heavy outperforms in 0 benchmarks, while Kimi K3 is better at 2 benchmarks (GPQA, Humanity's Last Exam).

Kimi K3 significantly outperforms across most benchmarks.

Tue Jul 21 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Kimi K3 specifies input context (1,048,576 tokens). Only Kimi K3 specifies output context (1,048,576 tokens).

xAI
Grok-4 Heavy
Input- tokens
Output- tokens
Moonshot AI
Kimi K3
Input1,048,576 tokens
Output1,048,576 tokens
Tue Jul 21 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Grok-4 Heavy and Kimi K3 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 K3

Text
Images
Audio
Video

Release Timeline

When each model was launched

Kimi K3 was released on 2026-07-16, while Grok-4 Heavy's release date is not specified.

We can confirm Kimi K3's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

Grok-4 Heavy

—

Kimi K3

Jul 16, 2026

5 days ago

Knowledge Cutoff

When training data ends

Grok-4 Heavy has a documented knowledge cutoff of 2024-12-31, while Kimi K3'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 K3's cutoff date.

Grok-4 Heavy

Dec 2024

Kimi K3

—

Outputs Comparison

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Key Takeaways

xAI

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

Moonshot AI
Larger context window (1,048,576 tokens)
Has open weights
Higher GPQA score (93.5% vs 88.4%)
Higher Humanity's Last Exam score (56.0% vs 50.7%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Grok-4 Heavy and Kimi K3 side-by-side, then vote on the output you prefer.

Grok-4 Heavy
✓ Preferred
Kimi K3
Open in Playground
AI Model Comparison Table
Feature
xAI
Grok-4 Heavy
Moonshot AI
Kimi K3

FAQ

Common questions about Grok-4 Heavy vs Kimi K3.

Which is better, Grok-4 Heavy or Kimi K3?

Kimi K3 significantly outperforms across most benchmarks. Grok-4 Heavy is made by xAI and Kimi K3 is made by Moonshot AI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Grok-4 Heavy compare to Kimi K3 in benchmarks?

Grok-4 Heavy scores AIME 2025: 100.0%, HMMT25: 96.7%, GPQA: 88.4%, LiveCodeBench: 79.4%, USAMO25: 61.9%. Kimi K3 scores MathVision: 97.8%, DeepSearchQA: 95.0%, GPQA: 93.5%, CharXiv-R: 91.3%, BrowseComp: 91.2%.

What are the context window sizes for Grok-4 Heavy and Kimi K3?

Grok-4 Heavy supports an unknown number of tokens and Kimi K3 supports 1.0M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Grok-4 Heavy and Kimi K3?

Key differences include licensing (Proprietary vs Unknown). See the full comparison above for benchmark-by-benchmark results.

Who makes Grok-4 Heavy and Kimi K3?

Grok-4 Heavy is developed by xAI and Kimi K3 is developed by Moonshot AI.

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