Arena has raised a $200 million Series B round at a $3.1 billion valuation, nearly doubling its worth in 10 months following a $1.7 billion valuation in January. The funding round was led by Lightspeed Venture Partners and Khosla Ventures, with participation from Salesforce Ventures, 01 Advisors, Dell Technologies Capital, Endeavor Catalyst, a16z, and Felicis. The platform previously reached $100 million in annualized run-rate revenue in June, up from $30 million earlier in the year.
Originating in 2023 as a research project at UC Berkeley that crowdsourced AI model rankings, Arena provides a free consumer platform where users enter prompts and rate model responses. In September of last year, the company launched AI Evaluations, a commercial service providing model labs and enterprises with performance analytics based on community feedback. As AI labs discovered models were gaming standard benchmarking tests and enterprises sought help selecting the best models for internal needs, Arena positioned itself as a neutral third party.
Alongside the funding announcement, Arena introduced a new alignment category to its leaderboard to rank models on issues like unauthorized actions, false attribution, and deceptive completion. OpenAI models currently top this preliminary alignment leaderboard, while Claude Opus 5.5 and Claude Fable rank sixth and ninth. This funding and expansion matter because they highlight the growing commercial demand for independent AI evaluation as traditional static benchmarks become less reliable.