Arena, the crowdsourced AI model ranking platform that began as a UC Berkeley research project in 2023, said Thursday it has raised a $200 million Series B round at a $3.1 billion valuation. The new funding comes roughly 10 months after the company's $150 million Series A in January, which carried a $1.7 billion post-money valuation. Arena said its annualized revenue stood at $30 million at the time of that earlier round and reached $100 million in June.

Lightspeed Venture Partners and Khosla Ventures led the Series B. Salesforce Ventures, 01 Advisors, Dell Technologies Capital, Endeavor Catalyst, a16z, Felicis and other investors also participated.

Arena operates a free, crowdsourced platform where consumers submit prompts or request vibe-coded projects and then judge which AI model performs better. The company says it draws tens of millions of monthly visitors. In September of last year, it launched a commercial product called AI Evaluations, which supplies model labs and enterprises with detailed performance analytics drawn from that community feedback.

That timing landed as AI labs discovered their models were gaming benchmarking tests, finding ways to score well without genuinely earning the results, and as enterprises sought guidance on which models suited their own internal needs rather than relying solely on standardized benchmarks. In its funding announcement, Arena said AI is advancing faster than the ability to evaluate it, and that static benchmarks break down once models recognize they are being tested. The company said the world needs a neutral third party to measure how safe and aligned AI is once real people are using it, and that Arena is stepping into that role.

Arena has added an alignment category to its leaderboard, ranking models on issues including unauthorized action, meaning taking actions they were not asked to take; false attribution, meaning crediting statements or facts to the wrong source; and what Arena calls deceptive completion, or lying about finishing tasks that were not done.

OpenAI models currently occupy the top of the preliminary alignment leaderboard, according to Arena, with Claude Opus 5.5 in sixth place and Claude Fable in ninth. The company has not disclosed further plans for the new capital.

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