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GPT OSS 20B vs Claude Opus 5.5

At a glance

OpenAI's compact open-weights model for efficient inference.

131K ctx$0.02/$0.09 per M

Anthropic's new flagship for demanding reasoning, coding, and long-horizon agentic work, succeeding Claude Opus 5.

1M ctx$4.00/$20.00 per M
Demos
All demos

No shared demos for these models yet.

AI Output
All AI outputs

No captured outputs for these models yet.

Benchmarks
See rankings
Reasoning
CodingInsufficient data
Sources:Epoch AI·OpenRouter· as of 2026-10-02
Cheaper100%
Reasoning & Knowledge
Graduate Science60.8%Factual Recall—
Math
Competition Math65.3%
Agentic
Terminal Tasks3.4%Novel Reasoning—
Reasoning
CodingInsufficient data
AgenticInsufficient data
Sources:Epoch AI·OpenRouter· as of 2026-10-02
Reasoning & Knowledge
Graduate Science49%90.6%Factual Recall72.2%
Math
Competition Math53%100.0%
Agentic
Terminal Tasks—Novel Reasoning92.5%
Specs
131K
Context
33K
Max output
Aug 2025
Released
1M
Context
128K
Max output
Sep 2026
Released
Capabilities
Vision
Audio
Reasoning
Vision
Audio
Reasoning
Pricing
Live pricing, shown before you run
Input100%$0.02/M tokens
Output100%$0.09/M tokens
Cache read96%$0.009/M tokens
Live pricing, shown before you run
Input$4.00/M tokens
Output$20.00/M tokens
Cache read$0.20/M tokens
Cache write$5.00/M tokens
Web search$0.01/search
Chat with GPT OSS 20BGo to model
Chat with Claude Opus 5.5Go to model
Frequently Asked Questions: GPT OSS 20B vs Claude Opus 5.5▼

Which is better, GPT OSS 20B or Claude Opus 5.5?

▼

Both GPT OSS 20B and Claude Opus 5.5 are capable AI models. The best choice depends on your specific use case: consider pricing, context window, speed, and which capabilities (vision, reasoning, audio) you need.

Which is cheaper, GPT OSS 20B or Claude Opus 5.5?

▼

GPT OSS 20B has a lower blended cost. GPT OSS 20B: $0.02 input / $0.09 output. Claude Opus 5.5: $4.00 input / $20.00 output.

Which has a larger context window, GPT OSS 20B or Claude Opus 5.5?

▼

Claude Opus 5.5 has a larger context window: GPT OSS 20B supports 131K tokens vs Claude Opus 5.5 at 1M tokens.

Do both GPT OSS 20B and Claude Opus 5.5 support vision?

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Claude Opus 5.5 supports vision/image input, but GPT OSS 20B does not.

What are the key differences between GPT OSS 20B and Claude Opus 5.5?

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Key differences: GPT OSS 20B is significantly cheaper; only Claude Opus 5.5 supports vision input. Compare full specs on this page.

Which model should I choose for my use case?

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If cost is your priority, choose the cheaper option. If you need the highest intelligence for complex tasks, pick the higher-scoring model. For long documents or codebases, choose the larger context window. You can try both GPT OSS 20B and Claude Opus 5.5 for free on idapt.app to see which performs better for your specific needs.

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