OpenAI's first reasoning model series, trained with reinforcement learning to think before answering; now deprecated in the API.
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OpenAI o1 is a series of large language models from OpenAI, introduced in September 2024, designed to spend more time reasoning before producing a response. It is trained with reinforcement learning to work through problems via an internal chain of thought, which improved results on tasks such as math, science, coding and ARC-style puzzles compared with earlier GPT models. Creators describe it as the first publicly available "thinking" model, with reduced hallucination on some tasks.
o1 was offered in ChatGPT and through the OpenAI API for developers. It accepts text and image input and returns text. The official page notes that the ChatGPT access information reflects the September 2024 launch and that o1 is now deprecated in the API, with newer reasoning models recommended instead.
Because it reasons before answering, responses are slower and costlier per request than non-reasoning models, and the reasoning tokens are not shown to users. It is a proprietary, closed-weights model.
Watch the moment: the exact second top creators show it. Videos load only when you press play, via youtube-nocookie.com.
Described as the first public thinking model, trained with reinforcement learning to reason through trial and error. It improved on tasks like ARC and coding and hallucinated less.
Closest neighbours by meaning, not just by category.
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