ChatGPT

ChatGPT is a conversational artificial intelligence assistant developed by OpenAI, released as a free research preview on 30 November 2022. Built on the company's Generative Pre-trained Transformer (GPT) family of large language models, it allows users to hold natural-language conversations, ask questions, generate text and code, analyse documents, and complete a wide range of tasks through a simple chat interface.^[1] ChatGPT is widely credited with bringing generative AI into mainstream public use and is among the most rapidly adopted consumer applications in history.^[3]

History

ChatGPT was launched on 30 November 2022 as a free "research preview" powered by GPT-3.5. Within five days it had passed one million users, and by January 2023 it was estimated to have reached 100 million monthly active users, making it the fastest-growing consumer application ever recorded at the time.^[3] In February 2023 OpenAI introduced ChatGPT Plus, a US$20-per-month subscription offering priority access and new features, and in March 2023 the more capable GPT-4 model became available to subscribers with image-understanding capabilities.^[4]

Subsequent milestones included the launch of ChatGPT Enterprise in August 2023, the introduction of custom GPTs and the GPT Store in November 2023, and the release of GPT-4o in May 2024, which added real-time voice conversation and made a frontier model available on the free tier for the first time.^[2][4] In August 2025 OpenAI released GPT-5, which unifies fast responses and deliberate reasoning within a single model, and it has since been succeeded by further GPT-5-series updates.^[2] By late 2025 ChatGPT was reported to have roughly 810 million weekly active users.^[3]

Technology

ChatGPT is built on OpenAI's GPT architecture, a family of transformer-based large language models trained on large corpora of text from the internet. The original service was fine-tuned from GPT-3.5 using reinforcement learning from human feedback (RLHF), a technique in which human raters rank model outputs and the model is trained to prefer responses that humans judge as helpful and harmless.^[1] The model predicts text token by token, generating responses that mimic human writing style, which enables tasks such as summarisation, translation, coding, and creative writing.^[5]

Later versions expanded the system into a multimodal assistant able to process text, images, and audio, and to browse the web, execute code, and use tools such as file analysis and image generation. The free tier provides access to a fast default model, while paid tiers (Plus, Pro, and Team/Enterprise) add higher usage limits, longer context windows, and access to reasoning models for complex problem-solving.^[2][5]

Applications and Impact

ChatGPT is used across education, business, software development, customer service, healthcare, and creative industries. Typical applications include drafting documents and emails, writing and debugging code, tutoring students, powering customer-support chatbots, and generating marketing content.^[5] The service also underpins OpenAI's developer API, through which organisations integrate GPT models into their own products. Its popularity triggered a wave of competing assistants from Google (Gemini), Anthropic (Claude), Meta, and others, and accelerated corporate investment in generative AI.^[2]

Concerns raised about ChatGPT include hallucination (the confident generation of false information), data-privacy risks, the potential for academic misconduct, and the impact of automation on jobs. These issues have driven debates over AI regulation in many countries.^[5]

>See Also

• Large Language Models
• OpenAI
• GPT-5
• Gemini
• Claude Language Model

References