Textbook of AI

ChatGPT is the conversational AI product released by OpenAI on 30 November 2022. It is a large language model, initially based on GPT-3.5, later GPT-4 and GPT-4o, fine-tuned with RLHF following the InstructGPT recipe to produce helpful, harmless and honest conversational responses. The product was released as a free research preview at chat.openai.com.

ChatGPT was the consumer launch that brought large language models to mass attention. It reached one million users in five days and 100 million monthly active users in two months, the fastest-growing consumer application in history at that time. The release reshaped public discourse about AI, transformed competitive pressure on every other AI organisation, accelerated regulatory engagement worldwide, and triggered an investment boom that has not abated as of 2026.

The technical innovation was less the underlying model, GPT-3.5 had been available via API for many months, than the conversational interface, the RLHF alignment that made the model reliably helpful, and the simple chat-style product that made the capabilities legible to non-technical users. The launch demonstrated that the bottleneck on AI deployment was not raw capability but interface and alignment.

The ChatGPT release initiated: a wave of frontier-model competitive launches (Claude in March 2023, Bard/Gemini in March 2023, LLaMA in February 2023); enterprise adoption of LLMs at unprecedented scale; regulatory engagement (EU AI Act, the Bletchley AI Safety Summit, the US AI Executive Order); a substantial public conversation about AI safety, alignment and the long-term implications of advanced AI.

As of 2026, ChatGPT remains OpenAI's flagship consumer product, with several hundred million weekly active users.