GPT-5.1

GPT-5.1 is an upgrade to OpenAI's GPT-5 series, rolled out as two complementary variants: GPT-5.1 Instant, the most-used conversational model, now warmer and more playful by default while staying clear and useful, and GPT-5.1 Thinking, the advanced reasoning model designed to be easier to understand, faster on routine tasks, and more persistent on complex ones. The release emphasizes a dual focus on measurable intelligence gains and a more enjoyable communication style, addressing direct user feedback that a great assistant should be both smart and pleasant to talk to. Alongside the model upgrade, OpenAI introduced more intuitive controls for shaping ChatGPT's tone so responses can match the conversational tone a user wants from one chat to the next.

Practically, GPT-5.1 fits teams and individuals who want a flexible assistant that can shift between quick, friendly exchanges and deeper reasoning without changing tools. Instant handles day-to-day questions, brainstorming, and lightweight instructions, while Thinking is aimed at multi-step problems that benefit from sustained analysis. The tone controls make it easier to tune outputs for different audiences, from concise professional replies to more expressive creative drafts, so the same model can adapt to writing, planning, coding help, and exploratory conversation within a single workflow.