GPT-5.5 Instant: 7 things to know about ChatGPT's New Default Model

On April 23, OpenAI released GPT-5.5, its most powerful model yet, built for professional users doing complex coding, research, and multi-step work. That model was not for everyone. On May 5, OpenAI started the rollout of GPT-5.5 Instant, replacing GPT-5.3 Instant as the default version of ChatGPT for all users, free or paid, with no settings change required.

Think of it as the everyday edition of OpenAI's frontier model. The full GPT-5.5 was built for heavy-duty professional tasks. GPT-5.5 Instant brings the same generation's improvements to the ChatGPT most people actually use every day for quick questions, writing help, meal planning, research, and everything in between.

Here are 7 things that changed.

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1. It makes up far fewer facts, especially on questions that matter most 

The biggest upgrade is accuracy. In OpenAI's internal testing, GPT-5.5 Instant produced 52.5% fewer made-up claims than its predecessor on questions about medicine, law, and finance. In real conversations that users had previously flagged for factual errors, wrong claims dropped by 37.3%. For a model used by hundreds of millions of people daily, including many who ask it health and legal questions, those are not small numbers.