o3-pro
o3-pro is a text generation model from OpenAI that applies more compute to reasoning, with a 200,000-token context window.
OpenAIExtended reasoning for complex, demanding tasks
o3-pro is a text generation model developed by OpenAI and released in June 2025. It is a variant of the o3 model family designed to apply additional compute during the reasoning process, making it suited for tasks that benefit from deeper, more deliberate thinking. The model supports a context window of 200,000 tokens and can produce responses up to 100,000 tokens in length.
o3-pro is intended for use cases that involve complex problem-solving, multi-step reasoning, mathematics, and scientific analysis where accuracy is prioritized over response speed. It exposes a configurable reasoning effort level, allowing users to adjust how much compute the model dedicates to a given request. Because of its extended reasoning approach, response latency is typically higher than standard chat models, making it a better fit for batch or asynchronous workflows than real-time conversational applications.
What o3-pro supports
Adjustable Reasoning Effort
Users can set the reasoning effort level via a select input, controlling how much compute the model applies before producing a response.
Large Context Window
Accepts up to 200,000 tokens of input, enabling analysis of long documents, codebases, or multi-turn conversation histories in a single request.
Long-Form Output
Supports responses up to 100,000 tokens, making it suitable for generating detailed reports, extensive code, or lengthy structured documents.
Multi-Step Reasoning
Applies chain-of-thought style reasoning internally before responding, which improves accuracy on problems requiring sequential logical steps.
Math and Science Tasks
Designed to handle quantitative and scientific problems where extended deliberation reduces errors compared to single-pass generation.
Code Generation
Capable of writing, reviewing, and debugging code across common programming languages, with reasoning applied to correctness and logic.
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Get Started FreeBenchmark scores
Scores represent accuracy — the percentage of questions answered correctly on each test.
| Benchmark | What it tests | Score |
|---|---|---|
| GPQA Diamond | PhD-level science questions (biology, physics, chemistry) | 84.5% |
Common questions about o3-pro
What is the context window size for o3-pro?
o3-pro supports a context window of 200,000 tokens, meaning it can process up to 200,000 tokens of combined input and conversation history in a single request.
What is the maximum response length?
The model can generate responses up to 100,000 tokens in a single output, which is suitable for long-form documents, detailed analyses, or extensive code generation.
What does the reasoning effort setting do?
The reasoning effort input lets you select how much compute o3-pro dedicates to thinking through a problem before responding. Higher effort generally improves accuracy on complex tasks but increases latency.
When was o3-pro released?
o3-pro was released in June 2025 by OpenAI.
Is o3-pro suitable for real-time chat applications?
Because o3-pro applies extended reasoning before generating a response, latency is higher than standard chat models. It is better suited for asynchronous or batch workflows where accuracy matters more than response speed.
What types of tasks is o3-pro best suited for?
o3-pro is designed for tasks requiring complex, multi-step reasoning such as mathematics, scientific analysis, detailed code generation, and long-document comprehension.
What people think about o3-pro
Community discussion around o3-pro's release was generally positive about its reasoning capabilities, with the r/singularity announcement thread noting interest in its performance on hard reasoning tasks. Some developers on r/LocalLLaMA raised practical concerns about the KYC requirement for API access, which added friction compared to standard model access.
Larger threads on r/ChatGPT from August 2025 reflect broader dissatisfaction with OpenAI's product and pricing decisions around the time of o3-pro's rollout, though these threads are not specific to o3-pro's technical performance. The KYC requirement and access restrictions appear to be recurring points of friction for developers evaluating the model for production use.
OpenAI just pulled the biggest bait-and-switch in AI history and I'm done.
OpenAI announce o3-pro release today
Deleted my subscription after two years. OpenAI lost all my respect.
OpenAI performs KYC to use the latest o3-pro via API
Documentation & links
Parameters & options
Used to give the model guidance on how many reasoning tokens it should generate before creating a response to the prompt. Low will favor speed and economical token usage, and high will favor more complete reasoning at the cost of more tokens generated and slower responses. The default value is medium, which is a balance between speed and reasoning accuracy.
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