GPT-5.3 Instant cuts hallucinations by 26.8% as OpenAI shifts focus from speed to accuracy

OpenAI's GPT-5.3 Instant — the company's most widely used model — reduces hallucinations by up to 26.8% compared to its predecessor, prioritizing accuracy and conversational reliability over raw performance gains, OpenAI says.GPT-5.3 Instant, which is essentially the default and is the most used model for ChatGPT users, also improves on tone, relevance and conversation with fewer refusals. It is available on both ChatGPT and on the API. Right now, only the Instant model will be upgraded to 5.3, but the company said it is working on updating the other models under ChatGPT, Thinking, and Pro to 5.3 “soon.” GPT-5.3 Instant cuts hallucinations by up to 26.8%OpenAI ran two internal evaluations: one across higher-stakes domains including medicine, finance, and law; the other drawing on user feed