OpenAI has quietly swapped out the engine powering ChatGPT for most users. Starting May 5, GPT-5.5 Instant replaces GPT-5.3 Instant as the default model used by hundreds of millions of people who open ChatGPT every day. No flashy demo, no new mode. Just a better version of the AI you already use.
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The headline improvement is accuracy. OpenAI says GPT-5.5 Instant produced 52.5% fewer hallucinated claims than GPT-5.3 Instant on internal high-stakes evaluations covering medicine, law, and finance. It also reduced inaccurate claims by 37.3% on difficult conversations previously flagged by users for factual errors. For a model that talks to this many people, that is a significant correction.
For anyone who had issues with ChatGPT over-explaining things with endless bullet points, GPT-5.5 Instant offers an improvement in this area by using 30.2% fewer words and 29.2% fewer lines than its older iteration. Additionally, OpenAI explicitly mentions that their chatbot no longer resorts to excessive emoji usage when generating answers.
It remembers more, and tells you what it remembers
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GPT-5.5 Instant has the ability to utilise its search feature to retrieve information from previous conversations, emails, and files to generate more personalised responses. However, the critical difference with this chatbot version is that OpenAI openly admits to doing this. Sources of memory provide information about input sources used to generate a particular answer and give users the opportunity to get rid of irrelevant information. For example, if the chatbot uses outdated information from a conversation six months ago, you can delete that data source.
Beyond accuracy, the model brings noticeable improvements to visual reasoning, math, and STEM-related questions. It is also designed to be smarter about deciding when to pull in live web search results.
GPT-5.5 Instant is rolling out to all ChatGPT users and is also available in the API as chat-latest. Paid users will keep access to GPT-5.3 Instant for three months through model configuration settings before it is retired. Gmail personalisation is live for Plus and Pro subscribers on web first, with free tier access coming in the weeks ahead.
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