OpenAI released GPT-4.5, which it described as its largest and most knowledgeable model to date, as a research preview. By scaling up unsupervised learning, the model was said to improve pattern recognition, breadth of knowledge, conversational naturalness and emotional intelligence (EQ), while reducing hallucinations. Unlike the reasoning-focused o-series, it followed a different track, and was initially offered to ChatGPT Pro users and API developers.
27February 2025
ModelConfirmed
GPT-4.5 released as a research preview
Participants
Tags
- llm
Sources
Later developments
14 July 2025 · Development
OpenAI removed GPT-4.5 from the API, having given notice on 14 April and allowed three months to migrate. It pointed developers to GPT-4.1, saying it matched or improved on GPT-4.5 across many key capabilities at lower latency and cost. GPT-4.5 left the API still labelled a research preview, never having graduated to a general release.
27 June 2026 · Development
In late June 2026 GPT-4.5 was removed from ChatGPT as well, after a 30-day sunset. OpenAI said it was "continuing to retire older models with limited usage in ChatGPT so we can better serve our newer, most capable models." With that, every GPT-4-generation model was gone from ChatGPT. Some users said they still wanted GPT-4.5 for writing and o3 for reasoning.