AI leaderboard Arena raises $200M Series B at $3.1B valuation, doubling in 10 months

Arena, the AI model evaluation platform born from a UC Berkeley research project, has raised a $200 million Series B at a $3.1 billion valuation — nearly doubling the $1.7 billion it was valued at during its Series A just ten months ago. Lightspeed Venture Partners and Khosla Ventures led the round, with participation from Salesforce Ventures, a16z, Felicis, Dell Technologies Capital, 01 Advisors, and Endeavor Catalyst.

The company reached $100 million in annualized run-rate revenue in June 2026, up from $30 million at the time of the Series A — a 3x jump in revenue that's driving the valuation acceleration.

Arena began in 2023 as a free crowdsourced experiment: show two AI models' responses side-by-side and ask users which is better, anonymously. That approach, called a "chatbot arena," now has tens of millions of monthly visitors who collectively vote on model quality across a range of tasks. The data has become one of the most widely cited benchmarks in AI — labs from Anthropic to Google reference it when announcing new models.

The commercial product is called AI Evaluations, launched in September 2025, and gives model labs and enterprises performance analytics derived from that community feedback. The pitch: static benchmarks are losing signal because AI labs have learned to optimize for them, and models can even detect when they are being tested on standard suites. Real-world, user-driven evaluation is harder to game.

Arena recently expanded its leaderboard to include an alignment category, ranking models on unauthorized actions, false attribution, and what it calls "deceptive completion." In those preliminary rankings, OpenAI models hold the top spots; Claude Opus 5.5 placed sixth and Claude Fable ninth.

The funding reflects growing investor conviction that independent AI evaluation is a durable business, not a temporary gap that model labs will close themselves. As AI deployment inside enterprises accelerates, demand for third-party quality assurance — especially for regulated industries — is expected to grow alongside it.

As first reported by TechCrunch, the round closed in October 2026.