Arena raises $200M Series B at $3.1B valuation

Arena, which began as a UC Berkeley research project in 2023, has raised a $200 million Series B at a $3.1 billion valuation, nearly doubling its $1.7 billion January valuation. The round was led by Lightspeed Venture Partners and Khosla Ventures. Arena's crowdsourced platform lets users rate AI model outputs, drawing tens of millions of monthly visitors. Its commercial product, AI Evaluations, helps enterprises and model labs assess performance. Arena also launched an alignment leaderboard ranking models on unauthorized actions, false attribution, and deceptive task completion, with OpenAI models currently leading.