OpenAI has expanded its reasoning model lineup with the release of o3-mini, a smaller but powerful addition to its "o" series that pushes the boundaries of what compact AI models can achieve.
Introduced as the most cost-efficient model in OpenAI's reasoning series, o3-mini delivers exceptional performance in STEM fields while maintaining the low cost and reduced latency of its predecessor. The model advances the boundaries of what small models can achieve, delivering exceptional STEM capabilities—with particular strength in science, math, and coding—all while maintaining the low cost and reduced latency of OpenAI o1‑mini.
Similar to its o1 predecessor, o3-mini has been optimized for STEM reasoning. With medium reasoning effort, it matches o1's performance in math, coding, and science, while delivering faster responses. Evaluations by expert testers showed that o3-mini produces more accurate and clearer answers, with stronger reasoning abilities, than o1-mini. External testers preferred o3-mini's answers over those from o1-mini more than half the time. The model also made 39% fewer "major mistakes" on "tough real-world questions" in A/B tests versus o1-mini, and produced "clearer" responses while delivering answers about 24% faster.
One of o3-mini's key innovations is its flexible reasoning capability. Developers can choose between three reasoning effort options—low, medium, and high—to optimize for their specific use cases. This flexibility allows o3-mini to "think harder" when tackling complex challenges or prioritize speed when latency is a concern.
The model is the first small reasoning model from OpenAI that supports highly requested developer features including function calling, structured outputs, and developer messages, making it production-ready from launch. As part of this release, OpenAI has tripled the rate limit for Plus and Team users from 50 messages per day with o1-mini to 150 messages per day with o3-mini. Additionally, o3-mini now works with search to find up-to-date answers with links to relevant web sources. Starting today, free plan users can also try o3-mini by selecting 'Reason' in the message composer or by regenerating a response—marking the first time a reasoning model has been made available to free users in ChatGPT.
The release of o3-mini comes at a strategic time for OpenAI, as the company prepares for the upcoming launch of its more powerful o3 and o4-mini models. In a post shared on X, CEO Sam Altman announced that the company will release two new models—o3 and o4-mini in the next couple of weeks, with GPT-5 now expected a few months later. As of April 2025, o3-mini has been fully replaced by o4-mini in ChatGPT and the API. o4-mini offers better performance on most benchmarks, adds native multimodal input, and retains tool compatibility—all while remaining faster and more affordable than o3.