ChatGPT

OpenAI was formally announced as a nonprofit on December 11, 2015 by Sam Altman, Elon Musk, Greg Brockman, Ilya Sutskever, Wojciech Zaremba and John Schulman, with roughly $1 billion in pledged funding. Seven years later, on November 30, 2022, OpenAI released ChatGPT as a free research preview built on GPT-3.5, framing it as an experiment to gather user feedback. Uptake was explosive: the chatbot reached one million users within five days and an estimated 100 million monthly users within two months, then the fastest consumer-app adoption on record.

OpenAI monetized the product quickly, launching the paid ChatGPT Plus tier in February 2023, followed a few weeks later by GPT-4 on March 14, 2023, which brought multimodal image understanding and improved reliability. Corporate turmoil followed in November 2023, when OpenAI's board fired Altman, saying he had not been "consistently candid" with them; he was reinstated five days later after most staff threatened to resign, and the board was subsequently reconstituted.

In May 2024, OpenAI shipped GPT-4o ("omni"), a natively multimodal model handling text, vision and audio that became free to all ChatGPT users. The launch was overshadowed by controversy: OpenAI's "Sky" demo voice drew accusations from actress Scarlett Johansson that it imitated her voice despite her having declined to participate, and within the same week chief scientist Ilya Sutskever and safety lead Jan Leike resigned, with OpenAI disbanding its "Superalignment" safety team amid Leike's public complaint that "safety culture and processes have taken a backseat to shiny products."

OpenAI then diversified its model lineup with the o1 reasoning series (September 2024), GPT-4.5 (February 2025) and GPT-4.1 (April 2025, the first production model with a 1-million-token context window), before unifying its chat and reasoning lines into GPT-5 on August 7, 2025. This period also brought serious legal exposure: The New York Times sued OpenAI and Microsoft for copyright infringement in December 2023, and in August 2025 the parents of 16-year-old Adam Raine sued OpenAI and Altman, alleging ChatGPT acted as their son's "suicide coach."

Iteration accelerated through late 2025 and 2026 — GPT-5.1 (November 2025), a rushed GPT-5.2 (December 2025, reportedly pushed forward by an internal "Code Red" memo after Google's Gemini 3 Pro launch), GPT-5.3-Codex (February 2026), GPT-5.4 (March 2026) and GPT-5.5 (April 2026). The current flagship, GPT-5.6, arrived in a limited preview on June 26, 2026 restricted to vetted partners at the Trump administration's request over cyber-capability concerns, before reaching general availability on July 9, 2026 as a three-tier family — Sol (flagship), Terra (balanced) and Luna (cost-efficient) — that OpenAI calls its strongest model yet across coding, science and cybersecurity.