Arena, the crowdsourced platform where users vote on which AI model gives the better answer, has raised $200 million at a $3.1 billion valuation, roughly double its value from ten months ago. The Series B, announced on October 8, was led by Lightspeed Venture Partners and Khosla Ventures, according to TechCrunch. Salesforce Ventures, 01 Advisors, Dell Technologies Capital, Endeavor Catalyst, a16z and Felicis were among the other investors.

The jump is steep. Arena, formerly known as LMArena, raised a $150 million Series A in January 2026 at a $1.7 billion post-money valuation. Its annualised revenue was $30 million at that time, and in June the company reported a $100 million annualised run rate.

The company began in 2023 as a UC Berkeley research project that crowdsourced rankings of AI models. Its main leaderboard is free for consumers: users submit prompts or ask for vibe-coded projects, then rate which model did better. Arena says it draws tens of millions of visitors a month. The money comes from its commercial product, AI Evaluations, launched in September 2025, which gives model labs and enterprises performance analytics built on community feedback.

Arena is now moving into safety. It has added an alignment category that ranks models on unauthorised action (doing more than was asked), false attribution (crediting statements to the wrong source) and “deceptive completion” (claiming to have finished tasks that were not done). In the preliminary standings, OpenAI models hold the top positions, while Anthropic’s Claude Opus 5.5 ranks sixth and Claude Fable ranks ninth.

The company argues that “static benchmarks break down once models recognize they’re being tested”, and says that once models reach real users, the world “needs a neutral third party to measure how safe and aligned AI actually is.” TechCrunch notes that AI labs have been found gaming benchmark tests, and that enterprises want evaluations tailored to their own needs. The report does not name Arena’s founders, cite any criticism of the company or name competitors. The revenue figures are the company’s own.