OpenAI Makes GPT-5.5 Instant the Default ChatGPT Model

On Tuesday, OpenAI released GPT-5.5 Instant, which will replace GPT-5.3 Instant as the default model in ChatGPT, according to a company announcement. The model is designed to deliver more accurate and concise responses while maintaining fast response times.

GPT-5.5 Instant reduces hallucinations in high-stakes areas such as law, medicine, and finance by 52.5 percent compared to the previous version. It also improves accuracy by 37.3 percent on difficult prompts flagged for factual errors. Benchmark results show higher scores across reasoning and mathematics tests, including an 81.2 score on the AIME 2025 math test and improved performance on the multimodal MMMU-Pro benchmark.

The update enhances personalization by allowing the model to reference past chats, files, and connected Gmail accounts to provide more relevant answers. Users can now view and manage the memory sources used for context, deleting or correcting them as needed. Shared chats will not expose these memory sources to others.

GPT-5.5 Instant is available immediately through ChatGPT and the API under the name “chat-latest.” GPT-5.3 Instant will remain accessible for paid users for three months before being retired. The new personalization tools are rolling out to Plus and Pro users on the web, with mobile and additional user tiers to follow in the coming weeks.