GPT-4.5 Retires From ChatGPT Today, Ending the GPT-4 Era

After a 30-day sunset period announced in late May, OpenAI has formally retired GPT-4.5 from ChatGPT on June 27, 2026. The model had already been removed from the API back in July 2025, but this final cutoff removes it entirely from the consumer ChatGPT experience, including custom GPTs that still referenced it.

Existing conversations that used GPT-4.5 will automatically continue using GPT-5.5, OpenAI's current default model. The transition is seamless for most users — GPT-5.5 matches or exceeds GPT-4.5 across all benchmarks, including reasoning, coding, and multimodal tasks. Custom GPT builders who relied on GPT-4.5-specific behavior may need to review their instructions, but OpenAI reports no major breaking changes.

The retirement also affects o3, which is scheduled for removal on August 26, 2026, following its own 90-day sunset. This means OpenAI is aggressively consolidating its model lineup around the GPT-5 family (GPT-5.5, GPT-5.5 Instant, and GPT-5.6), reducing the maintenance burden and simplifying the choice for developers and consumers alike.

For developers building on OpenAI's API, the impact is minimal since GPT-4.5 API access ended nearly a year ago. But for teams still referencing GPT-4.5 in documentation, model selectors, or fallback chains within ChatGPT, today is the hard deadline to update those references. The GPT-4 era — which began with the original GPT-4 launch in March 2023 — is officially over.