OpenAI rolls out GPT-5.5 Instant as ChatGPT’s new default model

OpenAI is replacing ChatGPT’s default model with GPT-5.5 Instant, a new system the company says is “smarter and more accurate, with clearer and more concise answers that feel better tailored to you.”

The rollout starts today for all ChatGPT users and also applies in the API under the name `chat-latest`.

OpenAI says GPT-5.5 Instant is taking over from GPT-5.3 Instant, which will stay available to paid users for three months before being retired.

The company says GPT-5.5 Instant is its latest daily-driver model, built to improve ordinary ChatGPT use rather than only heavy reasoning tasks.

OpenAI says the model produced 52.5% fewer hallucinated claims than GPT-5.3 Instant in internal tests covering medicine, law and finance, and cut inaccurate claims by 37.3% on difficult conversations that users had flagged as factual errors.

OpenAI also says the model is stronger at image and photo analysis, STEM questions and deciding when to use web search.

This was quite a social launch event at OpenAI, as one of the visitors posted this on X:

"5.5 party, on 5/5 at 5.55. Celebrating GPT 5.5. Perfect planning!!"

Credit: Marina Mogilko on X

The launch also comes with a broader personalization push. OpenAI says GPT-5.5 Instant uses context from past chats more effectively and can draw on connected files and Gmail for Plus and Pro users on the web, with mobile support coming soon.

The company says those personalization features will expand to Free, Go, Business and Enterprise users in the coming weeks, while memory sources are rolling out across all consumer plans on the web and soon on mobile.

OpenAI is also signaling a tougher safety posture around the model.

Its system card says GPT-5.5 Instant is the first Instant model treated as “High capability” in the company’s cybersecurity and biological and chemical preparedness categories, with safeguards added accordingly.

OpenAI’s safety documentation also says there is no GPT-5.4 Instant, and that GPT-5.5 Instant is being baselined against GPT-5.3 Instant.

The shift matters because Instant is the model most ChatGPT users will encounter first, which makes even small changes in clarity, tone and factuality visible across the product.

OpenAI is betting that a more concise default, paired with more personalization and less verbosity, will matter more in day-to-day use than a model that is merely larger or more complex.