o3-pro
OpenAI's most powerful reasoning model, designed to tackle the hardest problems with deeper thinking, multimodal understanding, and autonomous tool use.
OpenAI Deep reasoning for complex, high-stakes tasks
o3-pro is a text generation model developed by OpenAI, released on June 10, 2025. It is built around a reasoning-first architecture that performs iterative self-reflection before producing a response, simulating multiple solution paths and evaluating potential flaws rather than generating a single-pass output. The model accepts both text and image inputs and supports a 200,000-token context window. It also includes autonomous tool use, allowing it to independently invoke capabilities like Python execution, file analysis, and web retrieval.
o3-pro is designed for tasks that require sustained, multi-step reasoning — including mathematics, software engineering, scientific research, and legal analysis. It supports structured outputs and function calling, making it suitable for integration into developer pipelines and agentic workflows. Access to the model via API requires identity verification (KYC) from OpenAI. It is best suited for developers, researchers, and enterprises that need reliable, deeply reasoned outputs on complex problems.
What o3-pro supports
Multi-Stage Reasoning
Performs iterative self-reflection before responding, simulating multiple solution paths and evaluating potential flaws rather than producing a single-pass output.
Multimodal Input
Accepts both text and image inputs, enabling tasks that require visual understanding alongside language reasoning.
Autonomous Tool Use
Can independently decide when and how to invoke tools including Python execution, file analysis (PDF, CSV, JSON), and web retrieval to support agentic workflows.
Structured Outputs
Supports structured data generation and function calling, making it straightforward to integrate into developer pipelines that expect predictable output formats.
Large Context Window
Supports a 200,000-token context window, allowing it to process long documents, codebases, or multi-turn conversations in a single request.
Code Interpretation
Can execute and analyze code as part of its tool use capabilities, supporting tasks like debugging, code generation, and software engineering workflows.
Math & Science Reasoning
Evaluated on benchmarks including AIME (mathematics olympiad) and GPQA (graduate-level science), demonstrating step-wise symbolic and analytical reasoning.
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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, allowing it to handle long documents, extended conversations, and large codebases within a single request.
When was o3-pro released and what is its training data cutoff?
o3-pro was released on June 10, 2025. The metadata lists a training date of June 2025, though OpenAI has not publicly specified an exact knowledge cutoff date for this model.
Does accessing o3-pro via API require any special verification?
Yes. OpenAI requires identity verification (KYC — Know Your Customer) to access o3-pro through the API, which is an additional step compared to standard API access for other OpenAI models.
What input types does o3-pro support?
o3-pro accepts both text and image inputs, making it a multimodal model capable of handling tasks that involve visual content alongside natural language.
What kinds of tasks is o3-pro best suited for?
o3-pro is designed for complex, multi-step tasks such as mathematics, scientific research, software engineering, legal analysis, and agentic workflows that require autonomous tool use and structured output generation.
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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