GPT

GPT (Generative Pre-trained Transformer) is OpenAI's flagship line of large language models. The series began with GPT-1 (2018) and has progressed through GPT-2 (2019), GPT-3 (2020), GPT-3.5 (2022, powering the original ChatGPT), GPT-4 (2023), and GPT-4o (2024). The o-series (o1, o3) extends GPT with chain-of-thought reasoning. GPT models are available via the OpenAI API, ChatGPT, and Microsoft Copilot.