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Gemini 3.5 Flash vs Seed 2.1 Pro

Gemini 3.5 Flash and Seed 2.1 Pro are closely matched at 43.6 and 47.0 on the LLM Stats Score.

Google · ByteDance · Updated for 2026

Which is better?

Gemini 3.5 Flash and Seed 2.1 Pro are closely matched on the overall LLM Stats Score at 43.6 and 47.0.

In the 6 individual benchmarks reported for both models, Seed 2.1 Pro wins 4; this is a narrower head-to-head signal than the composite indexes.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose Gemini 3.5 Flash

  • you want predictable pricing at $1.50/M input and $9.00/M output

Choose Seed 2.1 Pro

  • you value its reported benchmark strengths — it wins 4 of 6 exact shared results
  • you want the most recent training data — it shipped Jun 2026

At a glance

The differences that matter most.

Gemini 3.5 Flash
Google
Seed 2.1 Pro
ByteDance
Core performance indexes
LLM Stats Score
43.6
#34
47.0
#20
Reasoning
44.4
#31
47.9
#18
Coding
33.8
#32
36.0
#25
Agents
31.5
#26
33.1
#22
Cost, coverage & limits
Benchmark wins
2 of 6
4 of 6
Input price
$1.50 / M
— / M
Output price
$9.00 / M
— / M
Context window
1,048,576
—

Capability indexes

Additional strengths measured across groups of related public benchmarks

6 shared
Index
Gemini 3.5 Flash
Seed 2.1 Pro
Math
30.7#67
39.8#15
Vision
31.9#22
34.9#10
Tool use
31.5#10
27.9#17
Long context
8.3#79
30.5#4
Multimodal
33.0#14
37.7#4
1 more shared indexes
Finance
31.0#19
33.9#7
Conservative TrueSkill rating · higher is betterHow scores work

Individual benchmarks

16 reported for Gemini 3.5 Flash · 94 for Seed 2.1 Pro

6 shared

Gemini 3.5 Flash outperforms in 2 benchmarks (MMMU-Pro, Toolathlon), while Seed 2.1 Pro is better at 4 benchmarks (CharXiv-R, Humanity's Last Exam, MCP Atlas, SWE-Bench Pro).

Seed 2.1 Pro shows notably better performance in the majority of benchmarks.

Fri Aug 28 2026 • llm-stats.com

Human preference

Blind head-to-head votes and playground preference scores

Context Window

Maximum input and output token capacity

Only Gemini 3.5 Flash specifies input context (1,048,576 tokens). Only Gemini 3.5 Flash specifies output context (65,536 tokens).

Google
Gemini 3.5 Flash
Input1,048,576 tokens
Output65,536 tokens
ByteDance
Seed 2.1 Pro
Input- tokens
Output- tokens
Fri Aug 28 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both Gemini 3.5 Flash and Seed 2.1 Pro support multimodal inputs.

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

Gemini 3.5 Flash

Text
Images
Audio
Video

Seed 2.1 Pro

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 3.5 Flash

Proprietary

Closed source

Seed 2.1 Pro

Proprietary

Closed source

Release Timeline

When each model was launched

Gemini 3.5 Flash was released on 2026-05-19, while Seed 2.1 Pro was released on 2026-06-24.

Seed 2.1 Pro is 1 month newer than Gemini 3.5 Flash.

Gemini 3.5 Flash

May 19, 2026

3 months ago

Seed 2.1 Pro

Jun 24, 2026

2 months ago

1mo newer

Knowledge Cutoff

When training data ends

Gemini 3.5 Flash has a documented knowledge cutoff of 2026-01-31, while Seed 2.1 Pro's cutoff date is not specified.

We can confirm Gemini 3.5 Flash's training data extends to 2026-01-31, but cannot make a direct comparison without Seed 2.1 Pro's cutoff date.

Gemini 3.5 Flash

Jan 2026

Seed 2.1 Pro

—

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Judge for yourself.

Run your own prompts against Gemini 3.5 Flash and Seed 2.1 Pro side-by-side, then vote on the output you prefer.

Gemini 3.5 Flash
✓ Preferred
Seed 2.1 Pro
Open in Playground

FAQ

Common questions about Gemini 3.5 Flash vs Seed 2.1 Pro.

Which is better, Gemini 3.5 Flash or Seed 2.1 Pro?

Gemini 3.5 Flash and Seed 2.1 Pro are closely matched on the LLM Stats Score at 43.6 and 47.0. Gemini 3.5 Flash is made by Google and Seed 2.1 Pro is made by ByteDance. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does Gemini 3.5 Flash compare to Seed 2.1 Pro in benchmarks?

Gemini 3.5 Flash scores CharXiv-R: 84.2%, MCP Atlas: 83.6%, MMMU-Pro: 83.6%, OSWorld-Verified: 78.4%, Terminal-Bench 2.0: 76.2%. Seed 2.1 Pro scores CharXiv-D: 95.5%, MathVision: 94.5%, MathVista: 90.7%, MathVerse: 89.7%, Video-MME: 89.2%.

What are the context window sizes for Gemini 3.5 Flash and Seed 2.1 Pro?

Gemini 3.5 Flash supports 1.0M tokens and Seed 2.1 Pro supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between Gemini 3.5 Flash and Seed 2.1 Pro?

Key differences include LLM Stats Score (43.6 vs 47.0). See the full comparison above for benchmark-by-benchmark results.

Who makes Gemini 3.5 Flash and Seed 2.1 Pro?

Gemini 3.5 Flash is developed by Google and Seed 2.1 Pro is developed by ByteDance.

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