OpenAI removed GPT-4.5 — the last member of the GPT-4 family — from ChatGPT on June 26, 2026, following a 30-day notice period the company issued on May 28. The model has also been pulled from any custom GPTs built on it.
What changed for users
Existing ChatGPT conversations that used GPT-4.5 now default to GPT-5.5. Developers using GPT-4.5 via the API are unaffected; OpenAI confirmed that no changes have been made on the API side.
Some users pushed back against the retirement, with several describing GPT-4.5’s writing style and tone as preferable to newer models. OpenAI has not commented on those concerns.
Why it matters
GPT-4 debuted in March 2023 and, within months, demonstrated that large language models could pass bar exams, write production code, analyze images, and hold coherent multi-turn conversations — capabilities that shifted public perception of what AI could do. GPT-4.5, released in February 2025, was the final iteration of that lineage before OpenAI shifted to the GPT-5 family.
Its removal from ChatGPT closes the consumer-facing chapter of a model generation that is widely credited with sparking the current wave of AI adoption. The GPT-4 family remains accessible through the API for developers who choose to continue using it.
OpenAI has separately announced that o3, its chain-of-thought reasoning model, is scheduled for retirement on August 26, 2026.