Model Comparison

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

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

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

Grok 4 Fast (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 Fast if…

  • you want the most recent training data — it shipped Aug 2025

Choose Kimi-k1.5 if…

  • you are already invested in the Moonshot AI ecosystem
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Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

Grok 4 Fast and Kimi-k1.5 don'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 Grok 4 Fast specifies input context (2,000,000 tokens). Only Grok 4 Fast specifies output context (30,000 tokens).

xAI
Grok 4 Fast
Input2,000,000 tokens
Output30,000 tokens
Moonshot AI
Kimi-k1.5
Input- tokens
Output- tokens
Sun Jun 07 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

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

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

Grok 4 Fast

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 Fast

Proprietary

Closed source

Kimi-k1.5

Proprietary

Closed source

Release Timeline

When each model was launched

Grok 4 Fast was released on 2025-08-28, while Kimi-k1.5 was released on 2025-01-20.

Grok 4 Fast is 7 months newer than Kimi-k1.5.

Grok 4 Fast

Aug 28, 2025

9 months ago

7mo newer
Kimi-k1.5

Jan 20, 2025

1.4 years ago

Knowledge Cutoff

When training data ends

Neither model specifies a knowledge cutoff date.

Unable to compare the recency of their training data.

No cutoff dates available

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

xAI
Larger context window (2,000,000 tokens)
Moonshot AI

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

Detailed Comparison

AI Model Comparison Table
Feature
xAI
Grok 4 Fast
Moonshot AI
Kimi-k1.5

FAQ

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

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

Grok 4 Fast (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 Fast compare to Kimi-k1.5 in benchmarks?

Grok 4 Fast scores SimpleQA: 95.0%, HMMT 2025: 93.3%, AIME 2025: 92.0%, GPQA: 85.7%, LiveCodeBench: 80.0%. Kimi-k1.5 scores MATH-500: 96.2%, CLUEWSC: 91.4%, C-Eval: 88.3%, MMLU: 87.4%, IFEval: 87.2%.

What are the context window sizes for Grok 4 Fast and Kimi-k1.5?

Grok 4 Fast supports 2.0M tokens and Kimi-k1.5 supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

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

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

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