Model Comparison
Grok 4 Fast vs Kimi K3Which is better in 2026?
Kimi K3 significantly outperforms across most benchmarks. Grok 4 Fast is 21.8x cheaper per token.
Verdict: Grok 4 Fast vs Kimi K3 — which is better?
Grok 4 Fast (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 Fast outperforms in 0 benchmarks, while Kimi K3 is better at 3 benchmarks (BrowseComp, GPQA, Humanity's Last Exam). Kimi K3 significantly outperforms across most benchmarks.
On price, Grok 4 Fast is roughly 21.8x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Grok 4 Fast also accepts a larger context window (2,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Choose Grok 4 Fast if…
- cost matters — it's about 21.8x cheaper per token
- you process long inputs — it offers a 2,000,000 token context window
Choose Kimi K3 if…
- you want the strongest raw capability — it leads on 3 of 3 shared benchmarks
- you want the most recent training data — it shipped Jul 2026
Performance Benchmarks
Comparative analysis across standard metrics
Grok 4 Fast outperforms in 0 benchmarks, while Kimi K3 is better at 3 benchmarks (BrowseComp, GPQA, Humanity's Last Exam).
Kimi K3 significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, Grok 4 Fast ($0.20/1M tokens) is 15.0x cheaper than Kimi K3 ($3.00/1M tokens).
For output processing, Grok 4 Fast ($0.50/1M tokens) is 30.0x cheaper than Kimi K3 ($15.00/1M tokens).
In conclusion, Kimi K3 is more expensive than Grok 4 Fast.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Grok 4 Fast accepts 2,000,000 input tokens compared to Kimi K3's 1,048,576 tokens. Kimi K3 can generate longer responses up to 1,048,576 tokens, while Grok 4 Fast is limited to 30,000 tokens.
Input Capabilities
Supported data types and modalities
Both Grok 4 Fast and Kimi K3 support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Grok 4 Fast
Kimi K3
Release Timeline
When each model was launched
Grok 4 Fast was released on 2025-08-28, while Kimi K3 was released on 2026-07-16.
Kimi K3 is 11 months newer than Grok 4 Fast.
Aug 28, 2025
10 months ago
Jul 16, 2026
5 days ago
10mo newerKnowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
Grok 4 Fast is available from xAI. Kimi K3 is available from Moonshot AI.
Grok 4 Fast
Kimi K3
Outputs Comparison
Key Takeaways
Kimi K3
View detailsMoonshot AI
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against Grok 4 Fast and Kimi K3 side-by-side, then vote on the output you prefer.
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FAQ
Common questions about Grok 4 Fast vs Kimi K3.