Character.ai: The Transformer Paper Co-Author Who Left Google to Build a $1B AI Chatbot Platform in 16 Months

Noam Shazeer spent nearly two decades at Google, where he became one of the most influential AI researchers in the world. In 2017, he co-authored the "Attention Is All You Need" paper that introduced the transformer architecture — the foundation of virtually every major AI system today including ChatGPT and Google's own models.

Why He Left Google

Together with colleague Daniel de Freitas, who built Google's experimental chatbots Meena and LaMDA, Shazeer grew frustrated that Google refused to release their conversational AI to the public due to safety concerns. Despite pleas from CEO Sundar Pichai to stay, Shazeer and de Freitas left Google in November 2021 to found Character.AI with the mission of building "personalized superintelligence."

Explosive Launch

They launched the beta in September 2022, allowing users to create and chat with AI characters, real or fictional, in open-ended conversations. The product exploded: within two months, site visits grew four-fold to nearly 100 million monthly. By around two months post-launch the company was reporting a rate of roughly 1 billion words sent per day, and by around five months post-launch cumulative messages had crossed 2 billion, with the second billion arriving in a single month. No marketing, no ad spend, pure product virality.

Unicorn and the Google Return

By March 2023, just 16 months after founding, Character.AI closed a $150M Series A at a $1 billion valuation from a16z. Then in August 2024, in a dramatic twist, both Shazeer and de Freitas returned to Google (DeepMind) as part of a $2.7 billion licensing deal, while Character.AI continued operating independently.

• Founded: November 2021
• Beta launch: September 2022
• ~1B words/day: ~2 months post-launch; 2B+ cumulative messages: ~5 months post-launch
• $1B valuation: March 2023 (16 months from founding)
• Google licensing deal: $2.7B (August 2024)