GPT 4.5: How to Access and Use It

A new model drops every few months, and suddenly what seemed cutting-edge yesterday feels outdated.

GPT-4.5 launched in February 2025 as OpenAI’s largest GPT model for chat at the time, with stronger broad knowledge, natural conversation, and reduced hallucinations compared with GPT-4o.

In 2026, GPT-4.5 is no longer available in ChatGPT. OpenAI retired GPT-4.5 from ChatGPT on June 26, 2026. The gpt-4.5-preview API model had already been shut down on July 14, 2025.

If you’re searching for how to access GPT-4.5 today, this page explains what changed, how GPT-4.5 access worked, what the model was designed for, and which newer options replaced it.

What Is GPT-4.5?

GPT-4.5 was released as a research preview in February 2025 and was OpenAI’s largest GPT model for chat at launch. Unlike reasoning-first models such as o1, GPT-4.5 focused on scaling unsupervised learning to improve broad knowledge, natural conversation, understanding of user intent, and factual reliability.

GPT-4.5 arrived as OpenAI was pursuing two complementary approaches to model improvement: scaling unsupervised learning and scaling reasoning. GPT-4.5 focused on the first approach, while models such as o1 and o3-mini focused more heavily on reasoning.

For GPT-4.5, OpenAI scaled compute and data alongside architecture and optimization improvements. The result was broader knowledge, better understanding of user intent, fewer hallucinations, and more natural conversation compared with GPT-4o.

GPT-4.5 was not designed as a reasoning-first model. OpenAI positioned it as a research preview focused on scaling pre-training and unsupervised learning to improve broad knowledge, understanding of user intent, and natural conversation.

How to Access GPT-4.5

GPT-4.5 is no longer available in ChatGPT or through the OpenAI API. Here’s how GPT-4.5 access worked, and what changed in 2026.

Can You Use GPT-4.5 for Free?

No. GPT-4.5 is no longer available in ChatGPT on any plan. When OpenAI originally launched the model, access started with ChatGPT Pro and later expanded to other paid plans rather than the Free plan.

1. ChatGPT Pro Users ($200 Plan)

• GPT-4.5 first launched in ChatGPT for Pro users on February 27, 2025, before expanding to other paid plans.
• GPT-4.5 was retired from ChatGPT in June 2026, so a ChatGPT Pro subscription no longer provides access to the model.

2. ChatGPT+ ($20), ChatGPT EDU, and ChatGPT Enterprise

• GPT-4.5 later expanded beyond Pro to other paid ChatGPT plans, including Plus, Enterprise, and Edu. OpenAI confirmed Enterprise and Edu access on March 13, 2025.
• That access has since ended. GPT-4.5 was retired from ChatGPT in June 2026, so these plans no longer provide access to the model.

3. OpenAI API Access

• GPT-4.5 launched in the OpenAI API as gpt-4.5-preview in February 2025.
• OpenAI deprecated the model in April 2025 and shut down API access on July 14, 2025.
• OpenAI recommended GPT-4.1 as the replacement because it offered similar or better performance on many key capabilities at lower cost and latency.

4. Microsoft Partners

• Microsoft made GPT-4.5 Preview available through Azure OpenAI in February 2025.
• Microsoft also tested GPT-4.5 in a limited preview for Copilot Studio in March 2025.
• GPT-4.5 Preview was later retired from Azure OpenAI on July 14, 2025, with GPT-4.1 listed as the recommended replacement.

5. Access GPT-4.5 via Chatbase

GPT-4.5 became available on Chatbase in February 2025, giving teams another way to use the model with their own business knowledge and AI agents. GPT-4.5 is no longer listed in Chatbase’s current model catalog.

If you’re building an agent today, Chatbase supports newer GPT models, including GPT-5 Mini, GPT-5 Nano, GPT-5.5, GPT-5.6 Terra, and GPT-5.6 Luna. You can build an AI agent with your own data and choose a current model based on the workload.

OpenAI positioned GPT-4.5 as an improvement in broad knowledge, understanding of user intent, natural conversation, and factual reliability compared with GPT-4o.

GPT-4.5 was an evolution of OpenAI’s GPT pre-training approach rather than a new reasoning architecture. In OpenAI’s launch evaluations, it outperformed GPT-4o on benchmarks including GPQA, MMMU, and SWE-bench Verified.

In February 2025, Sam Altman described GPT-4.5 as OpenAI’s “last non-chain-of-thought model” and said the company planned to unify GPT-series and reasoning-model capabilities in GPT-5.

That direction later appeared in GPT-5, which OpenAI launched as a unified system that decides when to answer quickly and when to use deeper reasoning.

GPT Timeline: From GPT-3.5 to GPT-4.5

While OpenAI has released models like GPT-1, GPT-2, and GPT-3, the real turning point for AI's mass-market adoption came with GPT-3.5. This was the moment when AI truly became mainstream, powering ChatGPT and revolutionizing how people interacted with AI models.

November 2022 – GPT-3.5

• GPT-3.5 launched with ChatGPT, marking the start of mass-market AI adoption and setting the stage for conversational AI at scale.

March 2023 – GPT-4

• OpenAI introduced GPT-4, its first truly multimodal model, capable of processing both text and images.
• This release significantly improved reasoning, creativity, and problem-solving.

2023 – 2024: Iterative Updates (GPT-4 Turbo, GPT-4-0314, etc.)

• OpenAI refined GPT-4 with models like GPT-4-0314 and GPT-4 Turbo, optimizing for speed, cost-efficiency, and longer context windows.
• These iterations focused on delivering better performance at scale.

2024 – The Rise of Reasoning Models

• Towards the end of 2024, OpenAI and other AI companies shifted towards reasoning-based models, where structured step-by-step thinking became the core competitive advantage.

February 2025 – GPT-4.5 Arrives

• GPT-4.5 launched on February 27, 2025 as a research preview and OpenAI’s largest GPT model for chat at the time. It scaled pre-training and unsupervised learning to improve broad knowledge, natural conversation, user-intent understanding, and factual reliability.

Get started: Build an AI agent with a current GPT model on Chatbase

Can You Try GPT-4.5 Right Now?

No. OpenAI retired GPT-4.5 from ChatGPT on June 26, 2026, and the gpt-4.5-preview API model had already been shut down on July 14, 2025.

GPT-4.5 still matters as part of OpenAI’s model history, especially because it represented a different scaling approach before the company moved toward unified reasoning systems such as GPT-5.

For current OpenAI model options, see our GPT-5.6 Sol guide. To test current GPT models with your own knowledge and workflows, you can sign in to Chatbase.