OpenAI has rolled out GPT-5.5 Instant as the new default model for ChatGPT, replacing GPT-5.3 across all user tiers. The update brings smarter, more accurate responses with clearer, more concise answers that feel tailored to individual users. This matters because hundreds of millions of people rely on Instant as their daily driver, so even incremental improvements have massive reach.

The company reports substantial factuality gains. Internal evaluations show GPT-5.5 produced 52.5% fewer hallucinated claims than its predecessor on high-stakes prompts covering medicine, law, and finance. It also reduced inaccurate claims by 37.3% on challenging conversations users had previously flagged. The model shows improvements in visual reasoning, math, and science, plus better judgment about when to use web search.

Responses are now tighter and more to-the-point without losing substance, while keeping the warmth that makes ChatGPT enjoyable. The system better leverages context from past chats, files, and connected Gmail so users don't have to repeat themselves. A new "memory sources" feature shows what context informed each response, letting users delete or correct outdated information.

GPT-5.5 is rolling out starting today to all ChatGPT users. Paid subscribers can still access GPT-5.3 through settings for three months before it retires. Enhanced personalization is heading to Plus and Pro users first, with mobile and other plans following.