OpenAI is launching GPT-4.5 today, its newest and largest AI language model. GPT-4.5 will be available as a research preview for ChatGPT Pro users to start. OpenAI is calling the release its “most knowledgeable model yet,” but initially warned that GPT-4.5 is not a frontier model and might not perform as well as o1 or o3-mini.
GPT-4.5 will have better writing capabilities, improved world knowledge, and what OpenAI calls a “refined personality over previous models.” OpenAI says interacting with GPT 4.5 will feel more “natural,” adding that the model is better at recognizing patterns and drawing connections, making it ideal for writing, programming, and “solving practical problems.”
However, OpenAI notes it won’t introduce enough new capabilities to be considered a frontier model. “GPT-4.5 is not a frontier model, but it is OpenAI’s largest LLM, improving on GPT-4’s computational efficiency by more than 10x,” OpenAI said in a document that leaked ahead of its announcement. “It does not introduce 7 net-new frontier capabilities compared to previous reasoning releases, and its performance is below that of o1, o3-mini, and deep research on most preparedness evaluations.” OpenAI has since removed this mention from an updated version of the document.
It was previously reported that OpenAI was using its o1 reasoning model, codenamed Strawberry, to train GPT-4.5 with synthetic data. OpenAI says it has trained GPT-4.5 “using new supervision techniques combined with traditional methods like supervised fine-tuning (SFT) and reinforcement learning from human feedback (RLHF), similar to those used for GPT-4o.”
Despite some of its limitations, GPT-4.5 hallucinates a lot less than GPT-4o, according to OpenAI, and slightly less than its o1 model. “We aligned GPT-4.5 to be a better collaborator, making conversations feel warmer, more intuitive, and emotionally nuanced,” Raphael Gontijo Lopes, a researcher at OpenAI, said during the company’s livestream. “To measure this, we asked human testers to evaluate it against GPT-4o, and GPT-4.5 outperformed on basically every category.”
In a post on X, OpenAI CEO Sam Altman acknowledged that GPT-4.5 is a “giant, expensive model” and that it “won’t crush benchmarks.”
Following its launch for Pro users, OpenAI says GPT-4.5 will roll out to Plus and Team users next week and then to Enterprise and Edu users after that. It’s also available now in Microsoft’s Azure AI Foundry platform, along with new models from Stability, Cohere, and Microsoft.
We revealed in Notepad last week that OpenAI was planning to launch GPT-4.5 by the end of February, and GPT-5 as soon as late May. OpenAI CEO Sam Altman has referred to GPT-5 as a “system that integrates a lot of our technology,” and it will include OpenAI’s new o3 reasoning model, which the company teased during its 12 days of Christmas announcements in December.
While OpenAI released o3-mini last month, OpenAI is only shipping o3 as part of its upcoming GPT-5 system. This aligns with OpenAI’s goal to combine its large language models to eventually create a more capable model that could be labeled as artificial general intelligence, or AGI.
Update, February 27th: Noted that OpenAI changed its GPT-4.5 system card and added information from Sam Altman.
