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GPT-5 Nano
GPT-5-Nano is the smallest and fastest variant in the GPT-5 system, optimized for developer tools, rapid interactions, and ultra-low latency environments. While limited in reasoning depth compared to its larger counterparts, it retains key instruction-following and safety features. It is the successor to GPT-4.1-nano and offers a lightweight option for cost-sensitive or real-time applications.
8/7/2025
400,000 tokens
Specifications
Modalities
Input
text
image
file
Output
text
Supported Parameters
include_reasoning
max_tokens
reasoning
response_format
seed
structured_outputs
tool_choice
tools
Max Output Tokens
128,000Reasoning Configuration
- Default
- Thinking on (effort: medium)
- Selectable effort levels
- highmediumlowminimal
- Turning thinking off
- Not possible (always thinks)
Data policy
- Prompt retention
- Unknown — we could not confirm
- Training
- Unknown — not declared
"Unknown" does not mean "safe". It means we could not confirm it.
Whether a provider trains on prompts is a declared value from our terms with them. Retention is determined from the upstream listing for every host this model can reach. Neither is guessed.
Frequently asked questions
- Is GPT-5 Nano available on FastMetal?
- Not at the moment. GPT-6.1 Sol, from the same lab, is available on the FastMetal API today.
- What is the context window of GPT-5 Nano?
- 400,000 tokens, shared between the prompt and the response.