On May 5, 2026, OpenAI announced GPT‑5.5 Instant as the new default model in ChatGPT for all users, replacing GPT‑5.3 Instant. The post positions Instant as the high-volume “daily driver” and summarizes quality, personalization, and rollout details.

What OpenAI says is new

According to the announcement:

  • Default swap — GPT‑5.5 Instant replaces GPT‑5.3 Instant as the default; rollout begins that day.
  • Factuality (internal evals) — OpenAI reports 52.5% fewer hallucinated claims than GPT‑5.3 Instant on high-stakes prompts (domains cited include medicine, law, and finance), and 37.3% fewer inaccurate claims on conversations users had flagged for factual errors.
  • Everyday tasks — The company highlights broader competence on routine work, including photo and image uploads, STEM questions, and deciding when to use web search.
  • Tone and length — OpenAI states responses can be tighter (it cites 30.2% fewer words and 29.2% fewer lines in a workplace-advice comparison shown in the article) while keeping a conversational feel, with fewer unnecessary follow-ups and less clutter.
  • Personalization — Instant is described as better at using context from past chats, files, and connected Gmail (where enabled), with memory sources UI so users can see what context shaped a reply and delete or correct it.

API and model continuity

OpenAI writes that GPT‑5.5 Instant ships in the API as chat-latest. Paid users retain access to GPT‑5.3 Instant via model configuration for three months before that model is retired.

Expanded personalization rollout

The post states that enhanced personalization from past chats, files, and Gmail is rolling out to Plus and Pro on the web first, coming soon to mobile, with plans to expand toward Free, Go, Business, and Enterprise over the coming weeks. Memory sources roll out across consumer plans on web and soon mobile, with regional variation possible for specific sources.

Frequently asked questions

Is GPT-5.5 Instant only for paying subscribers?

No. OpenAI describes it as the default for everyone in ChatGPT, while paid users get additional configuration options (including temporary access to 5.3 Instant).

Where are the hallucination statistics from?

They are OpenAI internal evaluations as described in the post—not independent third-party benchmarks.

Where should engineers verify API identifiers?

Use OpenAI’s live API documentation and release notes for chat-latest behavior, pricing, and regional availability.

Primary source: OpenAI — GPT‑5.5 Instant: smarter, clearer, and more personalized (May 5, 2026).