The product that changed everything
Product AnnouncementLaunched ChatGPT, a conversational AI fine-tuned from GPT-3.5 using RLHF. It reached 100M users in 2 months — the fastest-growing consumer application in history — and brought AI into mainstream public consciousness.
GPT-3.5 fine-tuned with RLHF using the InstructGPT methodology (SFT → RM → PPO).
The critical innovation wasn't technical — it was the UX decision to present the model as a conversational agent with memory within a session. This made the technology accessible to non-technical users.
ChatGPT reached 1 million users within 5 days and 100 million within 2 months, surpassing TikTok's growth rate.