GPT-5.5 Instant：より賢く、明確で、個別最適化されたモデル

We’re updating ChatGPT’s default model, available to everyone, to be smarter and more accurate, with clearer, more concise answers that feel better tailored to you.

Because Instant is the daily driver for hundreds of millions of people, small improvements make a big difference. This update makes everyday interactions more useful and more enjoyable: stronger and tighter answers across subject areas, a more natural conversational tone, and better use of the context you’ve already shared when personalization can help.

Instant is now more dependable, with significant improvements in factuality across the board and the largest gains in domains where accuracy matters most. In internal evaluations, GPT‑5.5 Instant produced 52.5% fewer hallucinated claims than GPT‑5.3 Instant on high-stakes prompts covering areas like medicine, law, and finance. It also reduced inaccurate claims by 37.3% on especially challenging conversations users had flagged for factual errors.

GPT‑5.5 Instant is a generally smarter model that’s more capable across everyday tasks, including improvements in analyzing photo and image uploads, answering STEM-related questions, and deciding when to use web search to provide a more useful answer.

These improvements are reflected in gains on evaluations across visual reasoning, math, and science:

With this update, the model’s responses are tighter and more to-the-point without losing substance, while keeping the warmth and personality that makes ChatGPT enjoyable to use. It can deliver the same information, often with more utility than previous models, while reducing the verbosity and overformatting that can make responses too long. It also asks fewer unnecessary follow-up questions and avoids things that can make responses feel cluttered, like gratuitous emojis.

Instant is now more effective at using context from past chats, files, and Gmail, if you have it connected, so answers feel more personally relevant while keeping you in control. It intelligently decides when a response can be improved with additional personalization and is faster at searching past conversations to find the right context, so you don’t have to repeat yourself as often. This is especially helpful for getting tailored suggestions and plans, or picking up where you left off for ongoing work.

We’re also introducing memory sources across all ChatGPT models, which give you visibility over what context was used to personalize responses with new controls. When a response is personalized, you can see what context was used, such as saved memories or past chats, and delete or correct it if something is outdated or no longer relevant.

Memory sources aren't shown to others if you choose to share a chat. You remain in control of what's in your memory: you can delete chats you no longer want to be cited, delete or change items in saved memories in settings, or use temporary chats that don't use or update your memory.

Memory sources are designed to make personalization easier to understand, but they may not show every factor that shaped an answer. For example, it may show you some of the most relevant past chats in sources instead of all the past chats it searched and referenced. We’ll continue improving this view to make it more comprehensive over time.

GPT‑5.5 Instant is rolling out starting today to all ChatGPT users, replacing GPT‑5.3 Instant as the default model, and in the API as chat-latest. For paid users, GPT‑5.3 Instant will remain available for three months, accessible through model configuration settings, before being retired.

Enhanced personalization from past chats, files, and connected Gmail is rolling out to Plus and Pro users on the web and coming soon to mobile with plans to expand to Free, Go, Business, and Enterprise in the coming weeks. Memory sources are rolling out across all ChatGPT consumer plans on the web and soon on mobile. Availability of specific personalization sources may vary by region.