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

Arena, which originated in 2023 as a UC Berkeley research project crowdsourcing rankings of AI models, has raised a $200 million Series B round at a $3.1 billion valuation, the company said Thursday. The round comes after Arena said it reached $100 million in annualized run-rate revenue in June.

The round was led by Lightspeed Venture Partners and Khosla Ventures, with Salesforce Ventures, 01 Advisors, Dell Technologies Capital, Endeavor Catalyst, a16z, Felicis, and others joining in. Arena previously announced a $150 million Series A in January at a $1.7 billion post-money valuation, when its annualized revenue was $30 million — meaning its valuation has nearly doubled in about 10 months.

Arena runs a crowdsourced platform, free for consumers, where people submit prompts or vibe-coded projects and rate which model performs better; the company says it has tens of millions of monthly visitors. In September of last year, it introduced a commercial product, AI Evaluations, which gives model labs and enterprises detailed performance analytics based on community feedback. The timing proved well-suited: this year, AI labs found their models gaming benchmark tests, and enterprises wanted help picking the best model for their own needs rather than relying only on standardized benchmarks.

“AI is advancing faster than our ability to evaluate it, and static benchmarks break down once models recognize they’re being tested,” the company said in its funding announcement. “The world needs a neutral third party to measure how safe and aligned AI actually is once it’s in the hands of real people. Arena is stepping into that role today.” To that end, Arena added a new “alignment” category to its leaderboard, ranking models on issues including unauthorized action, false attribution, and what it calls “deceptive completion” — lying about completing tasks it didn’t do. A slate of OpenAI’s models currently sits atop Arena’s preliminary alignment leaderboard, with Claude Opus 5.5 and Claude Fable in sixth and ninth place, respectively.

Why it matters

As AI labs face accusations of gaming standardized benchmarks, Arena’s bet on community-based evaluation — now extended to alignment and safety — positions it as a potential independent referee for an industry that increasingly needs one.