Arena

Arena — originally Chatbot Arena, and for a time LMArena — is the company behind the most widely cited public leaderboard for AI models. It began in 2023 as a research project at UC Berkeley's Sky Computing Lab (formerly LMSYS) and spun out into a company led by CEO Anastasios Angelopoulos and CTO Wei-Lin Chiang, with Berkeley professor and Databricks co-founder Ion Stoica as an advisor.

Arena's core idea is simple and influential: instead of scoring models only on fixed benchmarks, it lets people compare two anonymous model responses side by side and vote for the better one, aggregating millions of these human votes into a ranking. That crowd-sourced leaderboard has become the field's de facto scoreboard, cited by labs and the press whenever a new model ships.

The company raised a Series A in January 2026 at a 1.7 billion dollar valuation, led by Andreessen Horowitz and Felicis, and now runs a paid evaluations service alongside the free public leaderboard — selling deep model analytics to the same AI labs and enterprises that compete for the top spot. That positions Arena against human-data and evaluation firms like Scale AI and Surge as model-makers pour money into measuring and improving their systems.