ChatGPT unveils new default model “GPT-5.5 Instant” with improved “accuracy”

OpenAI has made GPT-5.5 Instant the new default model for ChatGPT users, replacing GPT-5.3 Instant.

The company says it reduces incorrect claims, improves image and STEM performance, and produces shorter, more direct answers.

New memory sources can draw on past chats, uploaded files, and Gmail context to make responses more personalized.

GPT-5.3 Instant will remain available to paid users for three months, while personalization rolls out first on the web for Plus and Pro users.