Model Comparison
Gemini 3.5 Flash-Lite vs Grok-4 Fast ReasoningWhich is better in 2026?
Comparing Gemini 3.5 Flash-Lite and Grok-4 Fast Reasoning across benchmarks, pricing, and capabilities.
Verdict: Gemini 3.5 Flash-Lite vs Grok-4 Fast Reasoning — which is better?
Gemini 3.5 Flash-Lite (by Google) and Grok-4 Fast Reasoning (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.
On price, Grok-4 Fast Reasoning is roughly 3.1x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Grok-4 Fast Reasoning also accepts a larger context window (2,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Choose Gemini 3.5 Flash-Lite if…
- you want the most recent training data — it shipped Jul 2026
Choose Grok-4 Fast Reasoning if…
- cost matters — it's about 3.1x cheaper per token
- you process long inputs — it offers a 2,000,000 token context window
Performance Benchmarks
Comparative analysis across standard metrics
Gemini 3.5 Flash-Lite and Grok-4 Fast Reasoningdon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Arena Performance
Human preference votes
Pricing Analysis
Price comparison per million tokens
For input processing, Gemini 3.5 Flash-Lite ($0.30/1M tokens) is 1.5x more expensive than Grok-4 Fast Reasoning ($0.20/1M tokens).
For output processing, Gemini 3.5 Flash-Lite ($2.50/1M tokens) is 5.0x more expensive than Grok-4 Fast Reasoning ($0.50/1M tokens).
In conclusion, Gemini 3.5 Flash-Lite is more expensive than Grok-4 Fast Reasoning.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Grok-4 Fast Reasoning accepts 2,000,000 input tokens compared to Gemini 3.5 Flash-Lite's 1,048,576 tokens. Gemini 3.5 Flash-Lite can generate longer responses up to 65,536 tokens, while Grok-4 Fast Reasoning is limited to 30,000 tokens.
Input Capabilities
Supported data types and modalities
Both Gemini 3.5 Flash-Lite and Grok-4 Fast Reasoning support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Gemini 3.5 Flash-Lite
Grok-4 Fast Reasoning
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Gemini 3.5 Flash-Lite was released on 2026-07-21, while Grok-4 Fast Reasoning was released on 2025-08-28.
Gemini 3.5 Flash-Lite is 11 months newer than Grok-4 Fast Reasoning.
Jul 21, 2026
4 days ago
10mo newerAug 28, 2025
11 months ago
Knowledge Cutoff
When training data ends
Gemini 3.5 Flash-Lite has a documented knowledge cutoff of 2026-03-31, while Grok-4 Fast Reasoning's cutoff date is not specified.
We can confirm Gemini 3.5 Flash-Lite's training data extends to 2026-03-31, but cannot make a direct comparison without Grok-4 Fast Reasoning's cutoff date.
Mar 2026
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Provider Availability
Gemini 3.5 Flash-Lite is available from Google. Grok-4 Fast Reasoning is available from xAI.
Gemini 3.5 Flash-Lite
Grok-4 Fast Reasoning
Outputs Comparison
Key Takeaways
No standout differentiators in the data we have for this pair.
Detailed Comparison
Interactive Arena
Judge for yourself.
Run your own prompts against Gemini 3.5 Flash-Lite and Grok-4 Fast Reasoning side-by-side, then vote on the output you prefer.
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FAQ
Common questions about Gemini 3.5 Flash-Lite vs Grok-4 Fast Reasoning.