Model Comparison
DeepSeek-V3.1 vs Grok 4 FastWhich is better in 2026?
Grok 4 Fast significantly outperforms across most benchmarks. Grok 4 Fast is 1.6x cheaper per token.
Verdict: DeepSeek-V3.1 vs Grok 4 Fast — which is better?
DeepSeek-V3.1 (by DeepSeek) and Grok 4 Fast (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.
DeepSeek-V3.1 outperforms in 0 benchmarks, while Grok 4 Fast is better at 7 benchmarks (AIME 2025, BrowseComp, GPQA, HMMT 2025, Humanity's Last Exam, LiveCodeBench, SimpleQA). Grok 4 Fast significantly outperforms across most benchmarks.
On price, Grok 4 Fast is roughly 1.6x 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 DeepSeek-V3.1 if…
- you need open weights you can self-host or fine-tune
Choose Grok 4 Fast if…
- you want the strongest raw capability — it leads on 7 of 7 shared benchmarks
- cost matters — it's about 1.6x cheaper per token
- you process long inputs — it offers a 2,000,000 token context window
- you want the most recent training data — it shipped Aug 2025
Performance Benchmarks
Comparative analysis across standard metrics
DeepSeek-V3.1 outperforms in 0 benchmarks, while Grok 4 Fast is better at 7 benchmarks (AIME 2025, BrowseComp, GPQA, HMMT 2025, Humanity's Last Exam, LiveCodeBench, SimpleQA).
Grok 4 Fast significantly outperforms across most benchmarks.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, DeepSeek-V3.1 ($0.27/1M tokens) is 1.4x more expensive than Grok 4 Fast ($0.20/1M tokens).
For output processing, DeepSeek-V3.1 ($1.00/1M tokens) is 2.0x more expensive than Grok 4 Fast ($0.50/1M tokens).
In conclusion, DeepSeek-V3.1 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 DeepSeek-V3.1's 163,840 tokens. DeepSeek-V3.1 can generate longer responses up to 163,840 tokens, while Grok 4 Fast is limited to 30,000 tokens.
Input Capabilities
Supported data types and modalities
Grok 4 Fast supports multimodal inputs, whereas DeepSeek-V3.1 does not.
Grok 4 Fast can handle both text and other forms of data like images, making it suitable for multimodal applications.
DeepSeek-V3.1
Grok 4 Fast
License
Usage and distribution terms
DeepSeek-V3.1 is licensed under MIT, while Grok 4 Fast uses a proprietary license.
License differences may affect how you can use these models in commercial or open-source projects.
MIT
Open weights
Proprietary
Closed source
Release Timeline
When each model was launched
DeepSeek-V3.1 was released on 2025-01-10, while Grok 4 Fast was released on 2025-08-28.
Grok 4 Fast is 8 months newer than DeepSeek-V3.1.
Jan 10, 2025
1.4 years ago
Aug 28, 2025
9 months ago
7mo newerKnowledge Cutoff
When training data ends
Neither model specifies a knowledge cutoff date.
Unable to compare the recency of their training data.
Provider Availability
DeepSeek-V3.1 is available from DeepInfra, Novita. Grok 4 Fast is available from xAI.
DeepSeek-V3.1
Grok 4 Fast
Outputs Comparison
Key Takeaways
DeepSeek-V3.1
View detailsDeepSeek
Detailed Comparison
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FAQ
Common questions about DeepSeek-V3.1 vs Grok 4 Fast.