Model Comparison

Gemini 1.5 Flash vs Grok-4 HeavyWhich is better in 2026?

Grok-4 Heavy significantly outperforms across most benchmarks.

Verdict: Gemini 1.5 Flash vs Grok-4 Heavy — which is better?

Gemini 1.5 Flash (by Google) and Grok-4 Heavy (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.

Gemini 1.5 Flash outperforms in 0 benchmarks, while Grok-4 Heavy is better at 1 benchmark (GPQA). Grok-4 Heavy significantly outperforms across most benchmarks.

Choose Gemini 1.5 Flash if…

  • you want predictable pricing at $0.15/M input and $0.60/M output

Choose Grok-4 Heavy if…

  • you want the strongest raw capability — it leads on 1 of 1 shared benchmarks
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Performance Benchmarks

Comparative analysis across standard metrics

1 benchmarks

Gemini 1.5 Flash outperforms in 0 benchmarks, while Grok-4 Heavy is better at 1 benchmark (GPQA).

Grok-4 Heavy significantly outperforms across most benchmarks.

Wed Jun 24 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only Gemini 1.5 Flash specifies input context (1,048,576 tokens). Only Gemini 1.5 Flash specifies output context (8,192 tokens).

Google
Gemini 1.5 Flash
Input1,048,576 tokens
Output8,192 tokens
xAI
Grok-4 Heavy
Input- tokens
Output- tokens
Wed Jun 24 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Gemini 1.5 Flash and Grok-4 Heavy support multimodal inputs.

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

Gemini 1.5 Flash

Text
Images
Audio
Video

Grok-4 Heavy

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.

Gemini 1.5 Flash

Proprietary

Closed source

Grok-4 Heavy

Proprietary

Closed source

Release Timeline

When each model was launched

Gemini 1.5 Flash was released on 2024-05-01, while Grok-4 Heavy's release date is not specified.

We can confirm Gemini 1.5 Flash's release timeline, but cannot make a direct age comparison without Grok-4 Heavy's release date.

Gemini 1.5 Flash

May 1, 2024

2.1 years ago

Grok-4 Heavy

—

Knowledge Cutoff

When training data ends

Gemini 1.5 Flash has a knowledge cutoff of 2023-11-01, while Grok-4 Heavy has a cutoff of 2024-12-31.

Grok-4 Heavy has more recent training data (up to 2024-12-31), making it potentially better informed about events through that date compared to Gemini 1.5 Flash (2023-11-01).

Gemini 1.5 Flash

Nov 2023

Grok-4 Heavy

Dec 2024

1.1 yr newer

Outputs Comparison

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Key Takeaways

Google
Larger context window (1,048,576 tokens)
xAI
Higher GPQA score (88.4% vs 51.0%)
GoogleGemini 1.5 Flash
xAIGrok-4 Heavy
Compare in Playground

Detailed Comparison

AI Model Comparison Table
Feature
Google
Gemini 1.5 Flash
xAI
Grok-4 Heavy

FAQ

Common questions about Gemini 1.5 Flash vs Grok-4 Heavy.

Which is better, Gemini 1.5 Flash or Grok-4 Heavy?

Grok-4 Heavy significantly outperforms across most benchmarks. Gemini 1.5 Flash is made by Google and Grok-4 Heavy is made by xAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Gemini 1.5 Flash compare to Grok-4 Heavy in benchmarks?

Gemini 1.5 Flash scores XSTest: 97.0%, FLEURS: 90.4%, HellaSwag: 86.5%, GSM8k: 86.2%, BIG-Bench Hard: 85.5%. Grok-4 Heavy scores AIME 2025: 100.0%, HMMT25: 96.7%, GPQA: 88.4%, LiveCodeBench: 79.4%, USAMO25: 61.9%.

What are the context window sizes for Gemini 1.5 Flash and Grok-4 Heavy?

Gemini 1.5 Flash supports 1.0M tokens and Grok-4 Heavy supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

Who makes Gemini 1.5 Flash and Grok-4 Heavy?

Gemini 1.5 Flash is developed by Google and Grok-4 Heavy is developed by xAI.

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