Specifically, GPT makes incorrect claims 9.6 percent of the time, compared to 12.9 percent for GPT-4o. And according to the GPT-5 system card, the new model’s hallucination rate is 26 percent lower than GPT-4o. In addition, GPT-5 had 44 percent fewer responses with “at least one major factual error.”

OpenAI has begun rolling out GPT-5, the latest iteration of its flagship language model, to all ChatGPT users.