Model Comparison

Seed 2.1 Pro vs GPT-5.5 ProWhich is better in 2026?

GPT-5.5 Pro significantly outperforms across most benchmarks.

Verdict: Seed 2.1 Pro vs GPT-5.5 Pro — which is better?

Seed 2.1 Pro (by ByteDance) and GPT-5.5 Pro (by OpenAI) 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.

Seed 2.1 Pro outperforms in 0 benchmarks, while GPT-5.5 Pro is better at 2 benchmarks (BrowseComp, Humanity's Last Exam). GPT-5.5 Pro significantly outperforms across most benchmarks.

Choose Seed 2.1 Pro if…

  • you want the most recent training data — it shipped Jun 2026

Choose GPT-5.5 Pro if…

  • you want the strongest raw capability — it leads on 2 of 2 shared benchmarks

Performance Benchmarks

Comparative analysis across standard metrics

2 benchmarks

Seed 2.1 Pro outperforms in 0 benchmarks, while GPT-5.5 Pro is better at 2 benchmarks (BrowseComp, Humanity's Last Exam).

GPT-5.5 Pro significantly outperforms across most benchmarks.

Fri Jul 17 2026 • llm-stats.com

Arena Performance

Human preference votes

Context Window

Maximum input and output token capacity

Only GPT-5.5 Pro specifies input context (1,050,000 tokens). Only GPT-5.5 Pro specifies output context (128,000 tokens).

ByteDance
Seed 2.1 Pro
Input- tokens
Output- tokens
OpenAI
GPT-5.5 Pro
Input1,050,000 tokens
Output128,000 tokens
Fri Jul 17 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both Seed 2.1 Pro and GPT-5.5 Pro support multimodal inputs.

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

Seed 2.1 Pro

Text
Images
Audio
Video

GPT-5.5 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.

Seed 2.1 Pro

Proprietary

Closed source

GPT-5.5 Pro

Proprietary

Closed source

Release Timeline

When each model was launched

Seed 2.1 Pro was released on 2026-06-24, while GPT-5.5 Pro was released on 2026-04-23.

Seed 2.1 Pro is 2 months newer than GPT-5.5 Pro.

Seed 2.1 Pro

Jun 24, 2026

3 weeks ago

2mo newer
GPT-5.5 Pro

Apr 23, 2026

2 months ago

Knowledge Cutoff

When training data ends

GPT-5.5 Pro has a documented knowledge cutoff of 2025-12-01, while Seed 2.1 Pro's cutoff date is not specified.

We can confirm GPT-5.5 Pro's training data extends to 2025-12-01, but cannot make a direct comparison without Seed 2.1 Pro's cutoff date.

Seed 2.1 Pro

—

GPT-5.5 Pro

Dec 2025

Outputs Comparison

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Key Takeaways

ByteDance

No standout differentiators in the data we have for this pair.

OpenAI
Larger context window (1,050,000 tokens)
Higher BrowseComp score (90.1% vs 86.2%)
Higher Humanity's Last Exam score (57.2% vs 55.7%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against Seed 2.1 Pro and GPT-5.5 Pro side-by-side, then vote on the output you prefer.

Seed 2.1 Pro
✓ Preferred
GPT-5.5 Pro
Open in Playground
AI Model Comparison Table
Feature
ByteDance
Seed 2.1 Pro
OpenAI
GPT-5.5 Pro

FAQ

Common questions about Seed 2.1 Pro vs GPT-5.5 Pro.

Which is better, Seed 2.1 Pro or GPT-5.5 Pro?

GPT-5.5 Pro significantly outperforms across most benchmarks. Seed 2.1 Pro is made by ByteDance and GPT-5.5 Pro is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does Seed 2.1 Pro compare to GPT-5.5 Pro in benchmarks?

Seed 2.1 Pro scores CharXiv-D: 95.5%, MathVision: 94.5%, MathVista: 90.7%, MathVerse: 89.7%, Video-MME: 89.2%. GPT-5.5 Pro scores BrowseComp: 90.1%, GDPval-MM: 82.3%, Humanity's Last Exam: 57.2%, FrontierMath: 39.6%, GeneBench: 33.2%.

What are the context window sizes for Seed 2.1 Pro and GPT-5.5 Pro?

Seed 2.1 Pro supports an unknown number of tokens and GPT-5.5 Pro supports 1.1M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

Who makes Seed 2.1 Pro and GPT-5.5 Pro?

Seed 2.1 Pro is developed by ByteDance and GPT-5.5 Pro is developed by OpenAI.

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