Arena, a platform for crowdsourced AI model rankings, secured $200 million in a Series B funding round. This investment brings the company's valuation to $3.1 billion, nearly doubling from the $1.7 billion valuation recorded during its January Series A round.
The funding round was led by Lightspeed Venture Partners and Khosla Ventures. Additional participants included Salesforce Ventures, 01 Advisors, Dell Technologies Capital, Endeavor Catalyst, a16z, and Felicis. The company reported an annualized run-rate revenue of $100 million as of June, compared to $30 million in January.
Originating as a 2023 research project at UC Berkeley, Arena now claims tens of millions of monthly visitors. The platform allows users to compare AI model outputs through prompts. In September 2025, the company launched AI Evaluations, a commercial service offering performance analytics to enterprises and model labs.
Arena has introduced an alignment category to its leaderboard to track issues such as unauthorized actions, false attribution, and deceptive completions. Currently, OpenAI models lead this ranking, while Claude Opus 5.5 and Claude Fable occupy the sixth and ninth positions, respectively.
