GPT-5.5 Instant in ChatGPT

GPT-5.5 Instant is now ChatGPT's default model, replacing GPT-5.3 Instant. Improves accuracy, clarity, conciseness, image understanding, STEM questions, and web search decisions. More factually reliable with tighter, more direct answers and reduced unnecessary formatting. Plus and Pro users on web can use context from past chats, files, and Gmail for more relevant responses. Paid users can continue using GPT-5.3 Instant for three months before retirement.