ChatGPT Gets Smarter Default: GPT-5.5 Instant Is Here

OpenAI has replaced ChatGPT’s default model with GPT-5.5 Instant, a significant upgrade that focuses on something users have been asking for since day one: fewer made-up answers.

What Changed

GPT-5.5 Instant replaces GPT-5.3 Instant as the model that powers ChatGPT for all users — free and paid. The headline improvement is accuracy: OpenAI says the new model produces 52.5% fewer hallucinated claims on high-stakes prompts in medicine, law, and finance. On conversations that users had previously flagged for factual errors, inaccurate claims dropped by 37.3%.

The model is also noticeably more concise. Responses use roughly 30% fewer words to make the same point, and OpenAI specifically targeted what it calls “gratuitous emojis” and unnecessary follow-up questions — two of the most common complaints about ChatGPT’s tone.

On benchmarks, GPT-5.5 Instant scores 81.2 on the AIME 2025 maths test, up from 65.4 for the previous version, and 76 on MMMU-Pro, up from 69.2.

Memory Sources: A New Transparency Feature

The most interesting new addition is “memory sources.” When ChatGPT uses personal context — from past conversations, uploaded files, or connected Gmail — it now shows you exactly which memories informed its answer. You can review, correct, or delete individual entries. This feature is currently available to Plus and Pro subscribers on the web, with broader rollout coming in the weeks ahead.

What This Means for You

If you use ChatGPT regularly, this is a meaningful upgrade you don’t need to do anything to get. Your conversations should feel tighter and more accurate, especially if you ask about topics where precision matters — health questions, legal queries, or financial planning.

The memory sources feature is worth exploring if you’re a paid subscriber. Being able to see why ChatGPT answered the way it did makes it easier to trust the output — or catch when it’s drawing on outdated context.

For developers, GPT-5.5 Instant is available via the API as the chat-latest model. GPT-5.3 Instant will remain available for paid API users for three months before being retired.

For more on how the full GPT-5.5 model compares to other AI tools, see our GPT-5.5 launch coverage. If you’re new to AI tools, our getting started guide covers the basics, or subscribe to our newsletter for daily updates.