GPT-4.5

GPT-4.5 (codenamed Orion)^[2] is a large language model within OpenAI's GPT series. It was released on February 27, 2025. GPT-4.5 can be accessed by Plus and Pro users through the model picker on web, mobile, and desktop, with plans to expand to other tiers. It can also be accessed via the OpenAI API or the OpenAI Developer Playground.^[3]

GPT-4.5

Developer	OpenAI
Year introduced	February 27, 2025; 2 months ago (2025-02-27)
Language/s	15 languages[1]

Overview

It was primarily trained using unsupervised learning, which improves its ability to recognize patterns, draw connections, and generate creative insights without reasoning. This method was combined with supervised fine-tuning and reinforcement learning from human feedback. It was trained using Microsoft Azure.^[3]

Sam Altman described GPT-4.5 as a "giant, expensive model".^[4] As of February 2025, through OpenAI's API it costs $75 per million input tokens and $150 per million output tokens, whereas GPT-4o only costs $2.50 per million input tokens and $10 per million output tokens.^[5]

The model was tested on the MMLU test set, which tested 15 different languages, namely Arabic, Bengali, Chinese, English, French, German, Hindi, Indonesian, Italian, Japanese, Korean, Portuguese, Spanish, Swahili, and Yoruba, with the model outperforming GPT-4o on all of them.^[1]

A pre-print study in March 2025 found that GPT-4.5 passed the Turing Test.^[6]

In April 2025, OpenAI announced that it was phasing out GPT-4.5 from API access in favor of GPT-4.1.^[7]

Reception

Cade Metz, writing for The New York Times, stated that the model "signifies the end of an era" and was "unlikely to generate as much excitement as GPT-4".^[8] Many other outlets, such as The Verge and Axios, also covered the model's release.^{[9][10][vague]}